* [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-27 10:36 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-27 10:36 UTC (permalink / raw)
To: Andrew Morton
Cc: KOSAKI Motohiro, Neil Brown, Con Kolivas, Jan Kara, Rik van Riel,
Peter Zijlstra, linux-kernel, linux-fsdevel, linux-mm, david,
hch, axboe
The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%.
This is not a user expected behavior. And it's inconsistent with
calc_period_shift(), which uses the plain vm_dirty_ratio value.
Let's rip the internal bound.
At the same time, fix balance_dirty_pages() to work with the
dirty_thresh=0 case. This allows applications to proceed when
dirty+writeback pages are all cleaned.
And ">" fits with the name "exceeded" better than ">=" does. Neil
think it is an aesthetic improvement as well as a functional one :)
CC: Jan Kara <jack@suse.cz>
CC: Rik van Riel <riel@redhat.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Proposed-by: Con Kolivas <kernel@kolivas.org>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-26 08:37:31.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-26 08:37:55.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
@@ -542,8 +536,8 @@ static void balance_dirty_pages(struct a
* the last resort safeguard.
*/
dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
- || (nr_reclaimable + nr_writeback >= dirty_thresh);
+ (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
+ || (nr_reclaimable + nr_writeback > dirty_thresh);
if (!dirty_exceeded)
break;
^ permalink raw reply [flat|nested] 35+ messages in thread* [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-27 10:36 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-27 10:36 UTC (permalink / raw)
To: Andrew Morton
Cc: KOSAKI Motohiro, Neil Brown, Con Kolivas, Jan Kara, Rik van Riel,
Peter Zijlstra, linux-kernel, linux-fsdevel, linux-mm, david,
hch, axboe
The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%.
This is not a user expected behavior. And it's inconsistent with
calc_period_shift(), which uses the plain vm_dirty_ratio value.
Let's rip the internal bound.
At the same time, fix balance_dirty_pages() to work with the
dirty_thresh=0 case. This allows applications to proceed when
dirty+writeback pages are all cleaned.
And ">" fits with the name "exceeded" better than ">=" does. Neil
think it is an aesthetic improvement as well as a functional one :)
CC: Jan Kara <jack@suse.cz>
CC: Rik van Riel <riel@redhat.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
Proposed-by: Con Kolivas <kernel@kolivas.org>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-26 08:37:31.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-26 08:37:55.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
@@ -542,8 +536,8 @@ static void balance_dirty_pages(struct a
* the last resort safeguard.
*/
dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
- || (nr_reclaimable + nr_writeback >= dirty_thresh);
+ (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
+ || (nr_reclaimable + nr_writeback > dirty_thresh);
if (!dirty_exceeded)
break;
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-27 10:36 ` Wu Fengguang
(?)
@ 2010-08-27 10:39 ` Peter Zijlstra
-1 siblings, 0 replies; 35+ messages in thread
From: Peter Zijlstra @ 2010-08-27 10:39 UTC (permalink / raw)
To: Wu Fengguang
Cc: Andrew Morton, KOSAKI Motohiro, Neil Brown, Con Kolivas,
Jan Kara, Rik van Riel, linux-kernel, linux-fsdevel, linux-mm,
david, hch, axboe
On Fri, 2010-08-27 at 18:36 +0800, Wu Fengguang wrote:
> The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%.
> This is not a user expected behavior. And it's inconsistent with
> calc_period_shift(), which uses the plain vm_dirty_ratio value.
>
> Let's rip the internal bound.
>
> At the same time, fix balance_dirty_pages() to work with the
> dirty_thresh=0 case. This allows applications to proceed when
> dirty+writeback pages are all cleaned.
>
> And ">" fits with the name "exceeded" better than ">=" does. Neil
> think it is an aesthetic improvement as well as a functional one :)
>
> CC: Jan Kara <jack@suse.cz>
> CC: Rik van Riel <riel@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Proposed-by: Con Kolivas <kernel@kolivas.org>
> Reviewed-by: Neil Brown <neilb@suse.de>
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-27 10:39 ` Peter Zijlstra
0 siblings, 0 replies; 35+ messages in thread
From: Peter Zijlstra @ 2010-08-27 10:39 UTC (permalink / raw)
To: Wu Fengguang
Cc: Andrew Morton, KOSAKI Motohiro, Neil Brown, Con Kolivas,
Jan Kara, Rik van Riel, linux-kernel, linux-fsdevel, linux-mm,
david, hch, axboe
On Fri, 2010-08-27 at 18:36 +0800, Wu Fengguang wrote:
> The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-27 10:39 ` Peter Zijlstra
0 siblings, 0 replies; 35+ messages in thread
From: Peter Zijlstra @ 2010-08-27 10:39 UTC (permalink / raw)
To: Wu Fengguang
Cc: Andrew Morton, KOSAKI Motohiro, Neil Brown, Con Kolivas,
Jan Kara, Rik van Riel, linux-kernel, linux-fsdevel, linux-mm,
david, hch, axboe
On Fri, 2010-08-27 at 18:36 +0800, Wu Fengguang wrote:
> The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-27 10:36 ` Wu Fengguang
@ 2010-08-27 13:47 ` Rik van Riel
-1 siblings, 0 replies; 35+ messages in thread
From: Rik van Riel @ 2010-08-27 13:47 UTC (permalink / raw)
To: Wu Fengguang
Cc: Andrew Morton, KOSAKI Motohiro, Neil Brown, Con Kolivas,
Jan Kara, Peter Zijlstra, linux-kernel, linux-fsdevel, linux-mm,
david, hch, axboe
On 08/27/2010 06:36 AM, Wu Fengguang wrote:
> The dirty_ratio was siliently limited in global_dirty_limits() to>= 5%.
> This is not a user expected behavior. And it's inconsistent with
> calc_period_shift(), which uses the plain vm_dirty_ratio value.
>
> Let's rip the internal bound.
>
> At the same time, fix balance_dirty_pages() to work with the
> dirty_thresh=0 case. This allows applications to proceed when
> dirty+writeback pages are all cleaned.
>
> And ">" fits with the name "exceeded" better than">=" does. Neil
> think it is an aesthetic improvement as well as a functional one :)
>
> CC: Jan Kara<jack@suse.cz>
> CC: Rik van Riel<riel@redhat.com>
> CC: Peter Zijlstra<a.p.zijlstra@chello.nl>
> Proposed-by: Con Kolivas<kernel@kolivas.org>
> Reviewed-by: Neil Brown<neilb@suse.de>
> Reviewed-by: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
--
All rights reversed
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-27 13:47 ` Rik van Riel
0 siblings, 0 replies; 35+ messages in thread
From: Rik van Riel @ 2010-08-27 13:47 UTC (permalink / raw)
To: Wu Fengguang
Cc: Andrew Morton, KOSAKI Motohiro, Neil Brown, Con Kolivas,
Jan Kara, Peter Zijlstra, linux-kernel, linux-fsdevel, linux-mm,
david, hch, axboe
On 08/27/2010 06:36 AM, Wu Fengguang wrote:
> The dirty_ratio was siliently limited in global_dirty_limits() to>= 5%.
> This is not a user expected behavior. And it's inconsistent with
> calc_period_shift(), which uses the plain vm_dirty_ratio value.
>
> Let's rip the internal bound.
>
> At the same time, fix balance_dirty_pages() to work with the
> dirty_thresh=0 case. This allows applications to proceed when
> dirty+writeback pages are all cleaned.
>
> And ">" fits with the name "exceeded" better than">=" does. Neil
> think it is an aesthetic improvement as well as a functional one :)
>
> CC: Jan Kara<jack@suse.cz>
> CC: Rik van Riel<riel@redhat.com>
> CC: Peter Zijlstra<a.p.zijlstra@chello.nl>
> Proposed-by: Con Kolivas<kernel@kolivas.org>
> Reviewed-by: Neil Brown<neilb@suse.de>
> Reviewed-by: KOSAKI Motohiro<kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
--
All rights reversed
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH v2] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-27 10:36 ` Wu Fengguang
@ 2010-08-29 0:19 ` Wu Fengguang
-1 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-29 0:19 UTC (permalink / raw)
To: Andrew Morton
Cc: KOSAKI Motohiro, Neil Brown, Con Kolivas, Jan Kara, Rik van Riel,
Peter Zijlstra, linux-kernel, linux-fsdevel, linux-mm, david,
hch, axboe
The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%.
This is not a user expected behavior. And it's inconsistent with
calc_period_shift(), which uses the plain vm_dirty_ratio value.
Let's rip the internal bound.
At the same time, fix balance_dirty_pages() to work with the
dirty_thresh=0 case. This allows applications to proceed when
dirty+writeback pages are all cleaned.
And ">" fits with the name "exceeded" better than ">=" does. Neil
think it is an aesthetic improvement as well as a functional one :)
v2: convert the background writeback checks, too. Just to be sure.
CC: Jan Kara <jack@suse.cz>
Proposed-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
fs/fs-writeback.c | 2 +-
mm/page-writeback.c | 16 +++++-----------
2 files changed, 6 insertions(+), 12 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-29 08:10:30.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-29 08:12:08.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
@@ -510,7 +504,7 @@ static void balance_dirty_pages(struct a
* catch-up. This avoids (excessively) small writeouts
* when the bdi limits are ramping up.
*/
- if (nr_reclaimable + nr_writeback <
+ if (nr_reclaimable + nr_writeback <=
(background_thresh + dirty_thresh) / 2)
break;
@@ -542,8 +536,8 @@ static void balance_dirty_pages(struct a
* the last resort safeguard.
*/
dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
- || (nr_reclaimable + nr_writeback >= dirty_thresh);
+ (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
+ || (nr_reclaimable + nr_writeback > dirty_thresh);
if (!dirty_exceeded)
break;
--- linux-next.orig/fs/fs-writeback.c 2010-08-29 08:12:51.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2010-08-29 08:12:53.000000000 +0800
@@ -574,7 +574,7 @@ static inline bool over_bground_thresh(v
global_dirty_limits(&background_thresh, &dirty_thresh);
return (global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
+ global_page_state(NR_UNSTABLE_NFS) > background_thresh);
}
/*
^ permalink raw reply [flat|nested] 35+ messages in thread* [PATCH v2] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-29 0:19 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-29 0:19 UTC (permalink / raw)
To: Andrew Morton
Cc: KOSAKI Motohiro, Neil Brown, Con Kolivas, Jan Kara, Rik van Riel,
Peter Zijlstra, linux-kernel, linux-fsdevel, linux-mm, david,
hch, axboe
The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%.
This is not a user expected behavior. And it's inconsistent with
calc_period_shift(), which uses the plain vm_dirty_ratio value.
Let's rip the internal bound.
At the same time, fix balance_dirty_pages() to work with the
dirty_thresh=0 case. This allows applications to proceed when
dirty+writeback pages are all cleaned.
And ">" fits with the name "exceeded" better than ">=" does. Neil
think it is an aesthetic improvement as well as a functional one :)
v2: convert the background writeback checks, too. Just to be sure.
CC: Jan Kara <jack@suse.cz>
Proposed-by: Con Kolivas <kernel@kolivas.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
fs/fs-writeback.c | 2 +-
mm/page-writeback.c | 16 +++++-----------
2 files changed, 6 insertions(+), 12 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-29 08:10:30.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-29 08:12:08.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
@@ -510,7 +504,7 @@ static void balance_dirty_pages(struct a
* catch-up. This avoids (excessively) small writeouts
* when the bdi limits are ramping up.
*/
- if (nr_reclaimable + nr_writeback <
+ if (nr_reclaimable + nr_writeback <=
(background_thresh + dirty_thresh) / 2)
break;
@@ -542,8 +536,8 @@ static void balance_dirty_pages(struct a
* the last resort safeguard.
*/
dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
- || (nr_reclaimable + nr_writeback >= dirty_thresh);
+ (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
+ || (nr_reclaimable + nr_writeback > dirty_thresh);
if (!dirty_exceeded)
break;
--- linux-next.orig/fs/fs-writeback.c 2010-08-29 08:12:51.000000000 +0800
+++ linux-next/fs/fs-writeback.c 2010-08-29 08:12:53.000000000 +0800
@@ -574,7 +574,7 @@ static inline bool over_bground_thresh(v
global_dirty_limits(&background_thresh, &dirty_thresh);
return (global_page_state(NR_FILE_DIRTY) +
- global_page_state(NR_UNSTABLE_NFS) >= background_thresh);
+ global_page_state(NR_UNSTABLE_NFS) > background_thresh);
}
/*
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 35+ messages in thread
* [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-20 3:25 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-20 3:25 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-kernel, linux-fsdevel, linux-mm, riel, david, hch, axboe,
Michael Rubin, Jan Kara, Neil Brown
The dirty_ratio was silently limited to >= 5%. This is not a user
expected behavior. Let's rip it.
It's not likely the user space will depend on the old behavior.
So the risk of breaking user space is very low.
CC: Jan Kara <jack@suse.cz>
CC: Neil Brown <neilb@suse.de>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-20 10:55:17.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-20 10:56:36.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
^ permalink raw reply [flat|nested] 35+ messages in thread* [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-20 3:25 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-20 3:25 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-kernel, linux-fsdevel, linux-mm, riel, david, hch, axboe,
Michael Rubin, Jan Kara, Neil Brown
The dirty_ratio was silently limited to >= 5%. This is not a user
expected behavior. Let's rip it.
It's not likely the user space will depend on the old behavior.
So the risk of breaking user space is very low.
CC: Jan Kara <jack@suse.cz>
CC: Neil Brown <neilb@suse.de>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
mm/page-writeback.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-20 10:55:17.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-20 10:56:36.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
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^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-20 3:25 ` Wu Fengguang
@ 2010-08-20 3:46 ` Rik van Riel
-1 siblings, 0 replies; 35+ messages in thread
From: Rik van Riel @ 2010-08-20 3:46 UTC (permalink / raw)
To: Wu Fengguang
Cc: Andrew Morton, linux-kernel, linux-fsdevel, linux-mm, david, hch,
axboe, Michael Rubin, Jan Kara, Neil Brown
On 08/19/2010 11:25 PM, Wu Fengguang wrote:
> The dirty_ratio was silently limited to>= 5%. This is not a user
> expected behavior. Let's rip it.
>
> It's not likely the user space will depend on the old behavior.
> So the risk of breaking user space is very low.
>
> CC: Jan Kara<jack@suse.cz>
> CC: Neil Brown<neilb@suse.de>
> Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
--
All rights reversed
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-20 3:46 ` Rik van Riel
0 siblings, 0 replies; 35+ messages in thread
From: Rik van Riel @ 2010-08-20 3:46 UTC (permalink / raw)
To: Wu Fengguang
Cc: Andrew Morton, linux-kernel, linux-fsdevel, linux-mm, david, hch,
axboe, Michael Rubin, Jan Kara, Neil Brown
On 08/19/2010 11:25 PM, Wu Fengguang wrote:
> The dirty_ratio was silently limited to>= 5%. This is not a user
> expected behavior. Let's rip it.
>
> It's not likely the user space will depend on the old behavior.
> So the risk of breaking user space is very low.
>
> CC: Jan Kara<jack@suse.cz>
> CC: Neil Brown<neilb@suse.de>
> Signed-off-by: Wu Fengguang<fengguang.wu@intel.com>
Acked-by: Rik van Riel <riel@redhat.com>
--
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^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-20 3:25 ` Wu Fengguang
@ 2010-08-20 4:13 ` KOSAKI Motohiro
-1 siblings, 0 replies; 35+ messages in thread
From: KOSAKI Motohiro @ 2010-08-20 4:13 UTC (permalink / raw)
To: Wu Fengguang
Cc: kosaki.motohiro, Andrew Morton, linux-kernel, linux-fsdevel,
linux-mm, riel, david, hch, axboe, Michael Rubin, Jan Kara,
Neil Brown
> The dirty_ratio was silently limited to >= 5%. This is not a user
> expected behavior. Let's rip it.
>
> It's not likely the user space will depend on the old behavior.
> So the risk of breaking user space is very low.
>
> CC: Jan Kara <jack@suse.cz>
> CC: Neil Brown <neilb@suse.de>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Thank you.
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-20 4:13 ` KOSAKI Motohiro
0 siblings, 0 replies; 35+ messages in thread
From: KOSAKI Motohiro @ 2010-08-20 4:13 UTC (permalink / raw)
To: Wu Fengguang
Cc: kosaki.motohiro, Andrew Morton, linux-kernel, linux-fsdevel,
linux-mm, riel, david, hch, axboe, Michael Rubin, Jan Kara,
Neil Brown
> The dirty_ratio was silently limited to >= 5%. This is not a user
> expected behavior. Let's rip it.
>
> It's not likely the user space will depend on the old behavior.
> So the risk of breaking user space is very low.
>
> CC: Jan Kara <jack@suse.cz>
> CC: Neil Brown <neilb@suse.de>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Thank you.
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
--
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^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-20 4:13 ` KOSAKI Motohiro
@ 2010-08-20 5:50 ` Con Kolivas
-1 siblings, 0 replies; 35+ messages in thread
From: Con Kolivas @ 2010-08-20 5:50 UTC (permalink / raw)
To: KOSAKI Motohiro
Cc: Wu Fengguang, Andrew Morton, linux-kernel, linux-fsdevel,
linux-mm, riel, david, hch, axboe
On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > The dirty_ratio was silently limited to >= 5%. This is not a user
> > expected behavior. Let's rip it.
> >
> > It's not likely the user space will depend on the old behavior.
> > So the risk of breaking user space is very low.
> >
> > CC: Jan Kara <jack@suse.cz>
> > CC: Neil Brown <neilb@suse.de>
> > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
>
> Thank you.
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
I have tried to do this in the past, and setting this value to 0 on some
machines caused the machine to come to a complete standstill with small
writes to disk. It seemed there was some kind of "minimum" amount of data
required by the VM before anything would make it to the disk and I never
quite found out where that blockade occurred. This was some time ago (3 years
ago) so I'm not sure if the problem has since been fixed in the VM since
then. I suggest you do some testing with this value set to zero before
approving this change.
Regards,
--
-ck
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-20 5:50 ` Con Kolivas
0 siblings, 0 replies; 35+ messages in thread
From: Con Kolivas @ 2010-08-20 5:50 UTC (permalink / raw)
To: KOSAKI Motohiro
Cc: Wu Fengguang, Andrew Morton, linux-kernel, linux-fsdevel,
linux-mm, riel, david, hch, axboe
On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > The dirty_ratio was silently limited to >= 5%. This is not a user
> > expected behavior. Let's rip it.
> >
> > It's not likely the user space will depend on the old behavior.
> > So the risk of breaking user space is very low.
> >
> > CC: Jan Kara <jack@suse.cz>
> > CC: Neil Brown <neilb@suse.de>
> > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
>
> Thank you.
> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
I have tried to do this in the past, and setting this value to 0 on some
machines caused the machine to come to a complete standstill with small
writes to disk. It seemed there was some kind of "minimum" amount of data
required by the VM before anything would make it to the disk and I never
quite found out where that blockade occurred. This was some time ago (3 years
ago) so I'm not sure if the problem has since been fixed in the VM since
then. I suggest you do some testing with this value set to zero before
approving this change.
Regards,
--
-ck
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-20 5:50 ` Con Kolivas
@ 2010-08-20 5:56 ` Wu Fengguang
-1 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-20 5:56 UTC (permalink / raw)
To: Con Kolivas
Cc: KOSAKI Motohiro, Andrew Morton, linux-kernel, linux-fsdevel,
linux-mm, riel, david, hch, axboe
On Fri, Aug 20, 2010 at 01:50:54PM +0800, Con Kolivas wrote:
> On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > expected behavior. Let's rip it.
> > >
> > > It's not likely the user space will depend on the old behavior.
> > > So the risk of breaking user space is very low.
> > >
> > > CC: Jan Kara <jack@suse.cz>
> > > CC: Neil Brown <neilb@suse.de>
> > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> >
> > Thank you.
> > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> I have tried to do this in the past, and setting this value to 0 on some
> machines caused the machine to come to a complete standstill with small
> writes to disk. It seemed there was some kind of "minimum" amount of data
> required by the VM before anything would make it to the disk and I never
> quite found out where that blockade occurred. This was some time ago (3 years
> ago) so I'm not sure if the problem has since been fixed in the VM since
> then. I suggest you do some testing with this value set to zero before
> approving this change.
Good point. I'll do more homework. Thanks for the reminding!
Thanks,
Fengguang
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-20 5:56 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-20 5:56 UTC (permalink / raw)
To: Con Kolivas
Cc: KOSAKI Motohiro, Andrew Morton, linux-kernel, linux-fsdevel,
linux-mm, riel, david, hch, axboe
On Fri, Aug 20, 2010 at 01:50:54PM +0800, Con Kolivas wrote:
> On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > expected behavior. Let's rip it.
> > >
> > > It's not likely the user space will depend on the old behavior.
> > > So the risk of breaking user space is very low.
> > >
> > > CC: Jan Kara <jack@suse.cz>
> > > CC: Neil Brown <neilb@suse.de>
> > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> >
> > Thank you.
> > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> I have tried to do this in the past, and setting this value to 0 on some
> machines caused the machine to come to a complete standstill with small
> writes to disk. It seemed there was some kind of "minimum" amount of data
> required by the VM before anything would make it to the disk and I never
> quite found out where that blockade occurred. This was some time ago (3 years
> ago) so I'm not sure if the problem has since been fixed in the VM since
> then. I suggest you do some testing with this value set to zero before
> approving this change.
Good point. I'll do more homework. Thanks for the reminding!
Thanks,
Fengguang
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-20 5:50 ` Con Kolivas
@ 2010-08-23 4:42 ` Neil Brown
-1 siblings, 0 replies; 35+ messages in thread
From: Neil Brown @ 2010-08-23 4:42 UTC (permalink / raw)
To: Con Kolivas
Cc: KOSAKI Motohiro, Wu Fengguang, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Fri, 20 Aug 2010 15:50:54 +1000
Con Kolivas <kernel@kolivas.org> wrote:
> On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > expected behavior. Let's rip it.
> > >
> > > It's not likely the user space will depend on the old behavior.
> > > So the risk of breaking user space is very low.
> > >
> > > CC: Jan Kara <jack@suse.cz>
> > > CC: Neil Brown <neilb@suse.de>
> > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> >
> > Thank you.
> > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> I have tried to do this in the past, and setting this value to 0 on some
> machines caused the machine to come to a complete standstill with small
> writes to disk. It seemed there was some kind of "minimum" amount of data
> required by the VM before anything would make it to the disk and I never
> quite found out where that blockade occurred. This was some time ago (3 years
> ago) so I'm not sure if the problem has since been fixed in the VM since
> then. I suggest you do some testing with this value set to zero before
> approving this change.
>
If it is appropriate to have a lower limit, that should be imposed where
the sysctl is defined in kernel/sysctl.c, not imposed after the fact where
the value is used.
As we now have dirty_bytes which over-rides dirty_ratio, there is little
cost in having a lower_limit for dirty_ratio - it could even stay at 5% -
but it really shouldn't be silent. Writing a number below the limit to the
sysctl file should fail.
NeilBrown
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-23 4:42 ` Neil Brown
0 siblings, 0 replies; 35+ messages in thread
From: Neil Brown @ 2010-08-23 4:42 UTC (permalink / raw)
To: Con Kolivas
Cc: KOSAKI Motohiro, Wu Fengguang, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Fri, 20 Aug 2010 15:50:54 +1000
Con Kolivas <kernel@kolivas.org> wrote:
> On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > expected behavior. Let's rip it.
> > >
> > > It's not likely the user space will depend on the old behavior.
> > > So the risk of breaking user space is very low.
> > >
> > > CC: Jan Kara <jack@suse.cz>
> > > CC: Neil Brown <neilb@suse.de>
> > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> >
> > Thank you.
> > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> I have tried to do this in the past, and setting this value to 0 on some
> machines caused the machine to come to a complete standstill with small
> writes to disk. It seemed there was some kind of "minimum" amount of data
> required by the VM before anything would make it to the disk and I never
> quite found out where that blockade occurred. This was some time ago (3 years
> ago) so I'm not sure if the problem has since been fixed in the VM since
> then. I suggest you do some testing with this value set to zero before
> approving this change.
>
If it is appropriate to have a lower limit, that should be imposed where
the sysctl is defined in kernel/sysctl.c, not imposed after the fact where
the value is used.
As we now have dirty_bytes which over-rides dirty_ratio, there is little
cost in having a lower_limit for dirty_ratio - it could even stay at 5% -
but it really shouldn't be silent. Writing a number below the limit to the
sysctl file should fail.
NeilBrown
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-23 4:42 ` Neil Brown
@ 2010-08-23 6:23 ` Wu Fengguang
-1 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-23 6:23 UTC (permalink / raw)
To: Neil Brown
Cc: Con Kolivas, KOSAKI Motohiro, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Mon, Aug 23, 2010 at 12:42:48PM +0800, Neil Brown wrote:
> On Fri, 20 Aug 2010 15:50:54 +1000
> Con Kolivas <kernel@kolivas.org> wrote:
>
> > On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > > expected behavior. Let's rip it.
> > > >
> > > > It's not likely the user space will depend on the old behavior.
> > > > So the risk of breaking user space is very low.
> > > >
> > > > CC: Jan Kara <jack@suse.cz>
> > > > CC: Neil Brown <neilb@suse.de>
> > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > >
> > > Thank you.
> > > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> >
> > I have tried to do this in the past, and setting this value to 0 on some
> > machines caused the machine to come to a complete standstill with small
> > writes to disk. It seemed there was some kind of "minimum" amount of data
> > required by the VM before anything would make it to the disk and I never
> > quite found out where that blockade occurred. This was some time ago (3 years
> > ago) so I'm not sure if the problem has since been fixed in the VM since
> > then. I suggest you do some testing with this value set to zero before
> > approving this change.
You are right, vm.dirty_ratio=0 will block applications for ever..
>
> If it is appropriate to have a lower limit, that should be imposed where
> the sysctl is defined in kernel/sysctl.c, not imposed after the fact where
> the value is used.
>
> As we now have dirty_bytes which over-rides dirty_ratio, there is little
> cost in having a lower_limit for dirty_ratio - it could even stay at 5% -
> but it really shouldn't be silent. Writing a number below the limit to the
> sysctl file should fail.
How about imposing an explicit bound of 1%? That's more natural and
its risk of breaking user space should be lower than 5%.
Thanks,
Fengguang
---
writeback: remove the internal 5% low bound on dirty_ratio
The dirty_ratio was silently limited in global_dirty_limits() to >= 5%. This
is not a user expected behavior. And it's inconsistent with calc_period_shift(),
which uses the plain vm_dirty_ratio value. So let's rip the internal bound.
At the same time, force a user visible low bound of 1% for the vm.dirty_ratio
interface. Applications trying to write 0 will be rejected with -EINVAL. This
will break user space applications if they
1) try to write 0 to vm.dirty_ratio
2) and check the return value
That is very weird combination, so the risk of breaking user space is low.
CC: Jan Kara <jack@suse.cz>
CC: Neil Brown <neilb@suse.de>
CC: Rik van Riel <riel@redhat.com>
CC: Con Kolivas <kernel@kolivas.org>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
kernel/sysctl.c | 2 +-
mm/page-writeback.c | 10 ++--------
2 files changed, 3 insertions(+), 9 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-20 20:14:11.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-23 10:31:01.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
--- linux-next.orig/kernel/sysctl.c 2010-08-23 14:06:11.000000000 +0800
+++ linux-next/kernel/sysctl.c 2010-08-23 14:07:30.000000000 +0800
@@ -1029,7 +1029,7 @@ static struct ctl_table vm_table[] = {
.maxlen = sizeof(vm_dirty_ratio),
.mode = 0644,
.proc_handler = dirty_ratio_handler,
- .extra1 = &zero,
+ .extra1 = &one,
.extra2 = &one_hundred,
},
{
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-23 6:23 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-23 6:23 UTC (permalink / raw)
To: Neil Brown
Cc: Con Kolivas, KOSAKI Motohiro, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Mon, Aug 23, 2010 at 12:42:48PM +0800, Neil Brown wrote:
> On Fri, 20 Aug 2010 15:50:54 +1000
> Con Kolivas <kernel@kolivas.org> wrote:
>
> > On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > > expected behavior. Let's rip it.
> > > >
> > > > It's not likely the user space will depend on the old behavior.
> > > > So the risk of breaking user space is very low.
> > > >
> > > > CC: Jan Kara <jack@suse.cz>
> > > > CC: Neil Brown <neilb@suse.de>
> > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > >
> > > Thank you.
> > > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> >
> > I have tried to do this in the past, and setting this value to 0 on some
> > machines caused the machine to come to a complete standstill with small
> > writes to disk. It seemed there was some kind of "minimum" amount of data
> > required by the VM before anything would make it to the disk and I never
> > quite found out where that blockade occurred. This was some time ago (3 years
> > ago) so I'm not sure if the problem has since been fixed in the VM since
> > then. I suggest you do some testing with this value set to zero before
> > approving this change.
You are right, vm.dirty_ratio=0 will block applications for ever..
>
> If it is appropriate to have a lower limit, that should be imposed where
> the sysctl is defined in kernel/sysctl.c, not imposed after the fact where
> the value is used.
>
> As we now have dirty_bytes which over-rides dirty_ratio, there is little
> cost in having a lower_limit for dirty_ratio - it could even stay at 5% -
> but it really shouldn't be silent. Writing a number below the limit to the
> sysctl file should fail.
How about imposing an explicit bound of 1%? That's more natural and
its risk of breaking user space should be lower than 5%.
Thanks,
Fengguang
---
writeback: remove the internal 5% low bound on dirty_ratio
The dirty_ratio was silently limited in global_dirty_limits() to >= 5%. This
is not a user expected behavior. And it's inconsistent with calc_period_shift(),
which uses the plain vm_dirty_ratio value. So let's rip the internal bound.
At the same time, force a user visible low bound of 1% for the vm.dirty_ratio
interface. Applications trying to write 0 will be rejected with -EINVAL. This
will break user space applications if they
1) try to write 0 to vm.dirty_ratio
2) and check the return value
That is very weird combination, so the risk of breaking user space is low.
CC: Jan Kara <jack@suse.cz>
CC: Neil Brown <neilb@suse.de>
CC: Rik van Riel <riel@redhat.com>
CC: Con Kolivas <kernel@kolivas.org>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
kernel/sysctl.c | 2 +-
mm/page-writeback.c | 10 ++--------
2 files changed, 3 insertions(+), 9 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-20 20:14:11.000000000 +0800
+++ linux-next/mm/page-writeback.c 2010-08-23 10:31:01.000000000 +0800
@@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
- else {
- int dirty_ratio;
-
- dirty_ratio = vm_dirty_ratio;
- if (dirty_ratio < 5)
- dirty_ratio = 5;
- dirty = (dirty_ratio * available_memory) / 100;
- }
+ else
+ dirty = (vm_dirty_ratio * available_memory) / 100;
if (dirty_background_bytes)
background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
--- linux-next.orig/kernel/sysctl.c 2010-08-23 14:06:11.000000000 +0800
+++ linux-next/kernel/sysctl.c 2010-08-23 14:07:30.000000000 +0800
@@ -1029,7 +1029,7 @@ static struct ctl_table vm_table[] = {
.maxlen = sizeof(vm_dirty_ratio),
.mode = 0644,
.proc_handler = dirty_ratio_handler,
- .extra1 = &zero,
+ .extra1 = &one,
.extra2 = &one_hundred,
},
{
--
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^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-23 6:23 ` Wu Fengguang
@ 2010-08-23 6:30 ` Con Kolivas
-1 siblings, 0 replies; 35+ messages in thread
From: Con Kolivas @ 2010-08-23 6:30 UTC (permalink / raw)
To: Wu Fengguang
Cc: Neil Brown, KOSAKI Motohiro, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Mon, 23 Aug 2010 04:23:59 pm Wu Fengguang wrote:
> On Mon, Aug 23, 2010 at 12:42:48PM +0800, Neil Brown wrote:
> > On Fri, 20 Aug 2010 15:50:54 +1000
> >
> > Con Kolivas <kernel@kolivas.org> wrote:
> > > On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > > > expected behavior. Let's rip it.
> > > > >
> > > > > It's not likely the user space will depend on the old behavior.
> > > > > So the risk of breaking user space is very low.
> > > > >
> > > > > CC: Jan Kara <jack@suse.cz>
> > > > > CC: Neil Brown <neilb@suse.de>
> > > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > > >
> > > > Thank you.
> > > > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > >
> > > I have tried to do this in the past, and setting this value to 0 on
> > > some machines caused the machine to come to a complete standstill with
> > > small writes to disk. It seemed there was some kind of "minimum" amount
> > > of data required by the VM before anything would make it to the disk
> > > and I never quite found out where that blockade occurred. This was some
> > > time ago (3 years ago) so I'm not sure if the problem has since been
> > > fixed in the VM since then. I suggest you do some testing with this
> > > value set to zero before approving this change.
>
> You are right, vm.dirty_ratio=0 will block applications for ever..
Indeed. And while you shouldn't set the lower limit to zero to avoid this
problem, it doesn't answer _why_ this happens. What is this "minimum write"
that blocks everything, will 1% be enough, and is it hiding another real bug
somewhere in the VM?
Regards,
Con
--
-ck
^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-23 6:30 ` Con Kolivas
0 siblings, 0 replies; 35+ messages in thread
From: Con Kolivas @ 2010-08-23 6:30 UTC (permalink / raw)
To: Wu Fengguang
Cc: Neil Brown, KOSAKI Motohiro, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Mon, 23 Aug 2010 04:23:59 pm Wu Fengguang wrote:
> On Mon, Aug 23, 2010 at 12:42:48PM +0800, Neil Brown wrote:
> > On Fri, 20 Aug 2010 15:50:54 +1000
> >
> > Con Kolivas <kernel@kolivas.org> wrote:
> > > On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > > > expected behavior. Let's rip it.
> > > > >
> > > > > It's not likely the user space will depend on the old behavior.
> > > > > So the risk of breaking user space is very low.
> > > > >
> > > > > CC: Jan Kara <jack@suse.cz>
> > > > > CC: Neil Brown <neilb@suse.de>
> > > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > > >
> > > > Thank you.
> > > > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > >
> > > I have tried to do this in the past, and setting this value to 0 on
> > > some machines caused the machine to come to a complete standstill with
> > > small writes to disk. It seemed there was some kind of "minimum" amount
> > > of data required by the VM before anything would make it to the disk
> > > and I never quite found out where that blockade occurred. This was some
> > > time ago (3 years ago) so I'm not sure if the problem has since been
> > > fixed in the VM since then. I suggest you do some testing with this
> > > value set to zero before approving this change.
>
> You are right, vm.dirty_ratio=0 will block applications for ever..
Indeed. And while you shouldn't set the lower limit to zero to avoid this
problem, it doesn't answer _why_ this happens. What is this "minimum write"
that blocks everything, will 1% be enough, and is it hiding another real bug
somewhere in the VM?
Regards,
Con
--
-ck
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-23 6:30 ` Con Kolivas
@ 2010-08-23 7:15 ` Wu Fengguang
-1 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-23 7:15 UTC (permalink / raw)
To: Con Kolivas
Cc: Neil Brown, KOSAKI Motohiro, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Mon, Aug 23, 2010 at 02:30:40PM +0800, Con Kolivas wrote:
> On Mon, 23 Aug 2010 04:23:59 pm Wu Fengguang wrote:
> > On Mon, Aug 23, 2010 at 12:42:48PM +0800, Neil Brown wrote:
> > > On Fri, 20 Aug 2010 15:50:54 +1000
> > >
> > > Con Kolivas <kernel@kolivas.org> wrote:
> > > > On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > > > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > > > > expected behavior. Let's rip it.
> > > > > >
> > > > > > It's not likely the user space will depend on the old behavior.
> > > > > > So the risk of breaking user space is very low.
> > > > > >
> > > > > > CC: Jan Kara <jack@suse.cz>
> > > > > > CC: Neil Brown <neilb@suse.de>
> > > > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > > > >
> > > > > Thank you.
> > > > > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > > >
> > > > I have tried to do this in the past, and setting this value to 0 on
> > > > some machines caused the machine to come to a complete standstill with
> > > > small writes to disk. It seemed there was some kind of "minimum" amount
> > > > of data required by the VM before anything would make it to the disk
> > > > and I never quite found out where that blockade occurred. This was some
> > > > time ago (3 years ago) so I'm not sure if the problem has since been
> > > > fixed in the VM since then. I suggest you do some testing with this
> > > > value set to zero before approving this change.
> >
> > You are right, vm.dirty_ratio=0 will block applications for ever..
>
> Indeed. And while you shouldn't set the lower limit to zero to avoid this
> problem, it doesn't answer _why_ this happens. What is this "minimum write"
> that blocks everything, will 1% be enough, and is it hiding another real bug
> somewhere in the VM?
Good question.
This simple change will unblock the application even with vm_dirty_ratio=0.
# echo 0 > /proc/sys/vm/dirty_ratio
# echo 0 > /proc/sys/vm/dirty_background_ratio
# vmmon nr_dirty nr_writeback nr_unstable
nr_dirty nr_writeback nr_unstable
0 444 1369
37 37 326
0 0 37
74 772 694
0 0 19
0 0 1406
0 0 23
0 0 0
0 370 186
74 1073 1221
0 12 26
0 703 1147
37 0 999
37 37 1517
0 888 63
0 0 0
0 0 20
37 0 0
37 74 1776
0 0 8
37 629 333
0 12 19
Even with it, the 1% explicit bound still looks reasonable for me.
Who will want to set it to 0%? That would destroy IO inefficient.
Thanks,
Fengguang
---
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -542,8 +536,8 @@ static void balance_dirty_pages(struct address_space *mapping,
* the last resort safeguard.
*/
dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
- || (nr_reclaimable + nr_writeback >= dirty_thresh);
+ (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
+ || (nr_reclaimable + nr_writeback > dirty_thresh);
if (!dirty_exceeded)
break;
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-23 7:15 ` Wu Fengguang
0 siblings, 0 replies; 35+ messages in thread
From: Wu Fengguang @ 2010-08-23 7:15 UTC (permalink / raw)
To: Con Kolivas
Cc: Neil Brown, KOSAKI Motohiro, Andrew Morton, linux-kernel,
linux-fsdevel, linux-mm, riel, david, hch, axboe
On Mon, Aug 23, 2010 at 02:30:40PM +0800, Con Kolivas wrote:
> On Mon, 23 Aug 2010 04:23:59 pm Wu Fengguang wrote:
> > On Mon, Aug 23, 2010 at 12:42:48PM +0800, Neil Brown wrote:
> > > On Fri, 20 Aug 2010 15:50:54 +1000
> > >
> > > Con Kolivas <kernel@kolivas.org> wrote:
> > > > On Fri, 20 Aug 2010 02:13:25 pm KOSAKI Motohiro wrote:
> > > > > > The dirty_ratio was silently limited to >= 5%. This is not a user
> > > > > > expected behavior. Let's rip it.
> > > > > >
> > > > > > It's not likely the user space will depend on the old behavior.
> > > > > > So the risk of breaking user space is very low.
> > > > > >
> > > > > > CC: Jan Kara <jack@suse.cz>
> > > > > > CC: Neil Brown <neilb@suse.de>
> > > > > > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > > > >
> > > > > Thank you.
> > > > > Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> > > >
> > > > I have tried to do this in the past, and setting this value to 0 on
> > > > some machines caused the machine to come to a complete standstill with
> > > > small writes to disk. It seemed there was some kind of "minimum" amount
> > > > of data required by the VM before anything would make it to the disk
> > > > and I never quite found out where that blockade occurred. This was some
> > > > time ago (3 years ago) so I'm not sure if the problem has since been
> > > > fixed in the VM since then. I suggest you do some testing with this
> > > > value set to zero before approving this change.
> >
> > You are right, vm.dirty_ratio=0 will block applications for ever..
>
> Indeed. And while you shouldn't set the lower limit to zero to avoid this
> problem, it doesn't answer _why_ this happens. What is this "minimum write"
> that blocks everything, will 1% be enough, and is it hiding another real bug
> somewhere in the VM?
Good question.
This simple change will unblock the application even with vm_dirty_ratio=0.
# echo 0 > /proc/sys/vm/dirty_ratio
# echo 0 > /proc/sys/vm/dirty_background_ratio
# vmmon nr_dirty nr_writeback nr_unstable
nr_dirty nr_writeback nr_unstable
0 444 1369
37 37 326
0 0 37
74 772 694
0 0 19
0 0 1406
0 0 23
0 0 0
0 370 186
74 1073 1221
0 12 26
0 703 1147
37 0 999
37 37 1517
0 888 63
0 0 0
0 0 20
37 0 0
37 74 1776
0 0 8
37 629 333
0 12 19
Even with it, the 1% explicit bound still looks reasonable for me.
Who will want to set it to 0%? That would destroy IO inefficient.
Thanks,
Fengguang
---
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -542,8 +536,8 @@ static void balance_dirty_pages(struct address_space *mapping,
* the last resort safeguard.
*/
dirty_exceeded =
- (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh)
- || (nr_reclaimable + nr_writeback >= dirty_thresh);
+ (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh)
+ || (nr_reclaimable + nr_writeback > dirty_thresh);
if (!dirty_exceeded)
break;
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
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^ permalink raw reply [flat|nested] 35+ messages in thread
* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
2010-08-23 6:23 ` Wu Fengguang
@ 2010-08-24 0:00 ` KOSAKI Motohiro
-1 siblings, 0 replies; 35+ messages in thread
From: KOSAKI Motohiro @ 2010-08-24 0:00 UTC (permalink / raw)
To: Wu Fengguang
Cc: kosaki.motohiro, Neil Brown, Con Kolivas, Andrew Morton,
linux-kernel, linux-fsdevel, linux-mm, riel, david, hch, axboe
> writeback: remove the internal 5% low bound on dirty_ratio
>
> The dirty_ratio was silently limited in global_dirty_limits() to >= 5%. This
> is not a user expected behavior. And it's inconsistent with calc_period_shift(),
> which uses the plain vm_dirty_ratio value. So let's rip the internal bound.
>
> At the same time, force a user visible low bound of 1% for the vm.dirty_ratio
> interface. Applications trying to write 0 will be rejected with -EINVAL. This
> will break user space applications if they
> 1) try to write 0 to vm.dirty_ratio
> 2) and check the return value
> That is very weird combination, so the risk of breaking user space is low.
I'm ok this one too. because I bet nobody use 0% dirty ratio on their production
server and/or their own desktop. (i.e. I don't mind lab machine crash)
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> CC: Jan Kara <jack@suse.cz>
> CC: Neil Brown <neilb@suse.de>
> CC: Rik van Riel <riel@redhat.com>
> CC: Con Kolivas <kernel@kolivas.org>
> CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
> kernel/sysctl.c | 2 +-
> mm/page-writeback.c | 10 ++--------
> 2 files changed, 3 insertions(+), 9 deletions(-)
>
> --- linux-next.orig/mm/page-writeback.c 2010-08-20 20:14:11.000000000 +0800
> +++ linux-next/mm/page-writeback.c 2010-08-23 10:31:01.000000000 +0800
> @@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
>
> if (vm_dirty_bytes)
> dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
> - else {
> - int dirty_ratio;
> -
> - dirty_ratio = vm_dirty_ratio;
> - if (dirty_ratio < 5)
> - dirty_ratio = 5;
> - dirty = (dirty_ratio * available_memory) / 100;
> - }
> + else
> + dirty = (vm_dirty_ratio * available_memory) / 100;
>
> if (dirty_background_bytes)
> background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
> --- linux-next.orig/kernel/sysctl.c 2010-08-23 14:06:11.000000000 +0800
> +++ linux-next/kernel/sysctl.c 2010-08-23 14:07:30.000000000 +0800
> @@ -1029,7 +1029,7 @@ static struct ctl_table vm_table[] = {
> .maxlen = sizeof(vm_dirty_ratio),
> .mode = 0644,
> .proc_handler = dirty_ratio_handler,
> - .extra1 = &zero,
> + .extra1 = &one,
> .extra2 = &one_hundred,
> },
> {
^ permalink raw reply [flat|nested] 35+ messages in thread* Re: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio
@ 2010-08-24 0:00 ` KOSAKI Motohiro
0 siblings, 0 replies; 35+ messages in thread
From: KOSAKI Motohiro @ 2010-08-24 0:00 UTC (permalink / raw)
To: Wu Fengguang
Cc: kosaki.motohiro, Neil Brown, Con Kolivas, Andrew Morton,
linux-kernel, linux-fsdevel, linux-mm, riel, david, hch, axboe
> writeback: remove the internal 5% low bound on dirty_ratio
>
> The dirty_ratio was silently limited in global_dirty_limits() to >= 5%. This
> is not a user expected behavior. And it's inconsistent with calc_period_shift(),
> which uses the plain vm_dirty_ratio value. So let's rip the internal bound.
>
> At the same time, force a user visible low bound of 1% for the vm.dirty_ratio
> interface. Applications trying to write 0 will be rejected with -EINVAL. This
> will break user space applications if they
> 1) try to write 0 to vm.dirty_ratio
> 2) and check the return value
> That is very weird combination, so the risk of breaking user space is low.
I'm ok this one too. because I bet nobody use 0% dirty ratio on their production
server and/or their own desktop. (i.e. I don't mind lab machine crash)
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> CC: Jan Kara <jack@suse.cz>
> CC: Neil Brown <neilb@suse.de>
> CC: Rik van Riel <riel@redhat.com>
> CC: Con Kolivas <kernel@kolivas.org>
> CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
> CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
> kernel/sysctl.c | 2 +-
> mm/page-writeback.c | 10 ++--------
> 2 files changed, 3 insertions(+), 9 deletions(-)
>
> --- linux-next.orig/mm/page-writeback.c 2010-08-20 20:14:11.000000000 +0800
> +++ linux-next/mm/page-writeback.c 2010-08-23 10:31:01.000000000 +0800
> @@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *
>
> if (vm_dirty_bytes)
> dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);
> - else {
> - int dirty_ratio;
> -
> - dirty_ratio = vm_dirty_ratio;
> - if (dirty_ratio < 5)
> - dirty_ratio = 5;
> - dirty = (dirty_ratio * available_memory) / 100;
> - }
> + else
> + dirty = (vm_dirty_ratio * available_memory) / 100;
>
> if (dirty_background_bytes)
> background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE);
> --- linux-next.orig/kernel/sysctl.c 2010-08-23 14:06:11.000000000 +0800
> +++ linux-next/kernel/sysctl.c 2010-08-23 14:07:30.000000000 +0800
> @@ -1029,7 +1029,7 @@ static struct ctl_table vm_table[] = {
> .maxlen = sizeof(vm_dirty_ratio),
> .mode = 0644,
> .proc_handler = dirty_ratio_handler,
> - .extra1 = &zero,
> + .extra1 = &one,
> .extra2 = &one_hundred,
> },
> {
--
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^ permalink raw reply [flat|nested] 35+ messages in thread
[parent not found: <201008241620.54048.kernel@kolivas.org>]
end of thread, other threads:[~2010-08-29 0:19 UTC | newest]
Thread overview: 35+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-08-27 10:36 [PATCH] writeback: remove the internal 5% low bound on dirty_ratio Wu Fengguang
2010-08-27 10:36 ` Wu Fengguang
2010-08-27 10:39 ` Peter Zijlstra
2010-08-27 10:39 ` Peter Zijlstra
2010-08-27 10:39 ` Peter Zijlstra
2010-08-27 13:47 ` Rik van Riel
2010-08-27 13:47 ` Rik van Riel
2010-08-29 0:19 ` [PATCH v2] " Wu Fengguang
2010-08-29 0:19 ` Wu Fengguang
-- strict thread matches above, loose matches on Subject: below --
2010-08-20 3:25 [PATCH] " Wu Fengguang
2010-08-20 3:25 ` Wu Fengguang
2010-08-20 3:46 ` Rik van Riel
2010-08-20 3:46 ` Rik van Riel
2010-08-20 4:13 ` KOSAKI Motohiro
2010-08-20 4:13 ` KOSAKI Motohiro
2010-08-20 5:50 ` Con Kolivas
2010-08-20 5:50 ` Con Kolivas
2010-08-20 5:56 ` Wu Fengguang
2010-08-20 5:56 ` Wu Fengguang
2010-08-23 4:42 ` Neil Brown
2010-08-23 4:42 ` Neil Brown
2010-08-23 6:23 ` Wu Fengguang
2010-08-23 6:23 ` Wu Fengguang
2010-08-23 6:30 ` Con Kolivas
2010-08-23 6:30 ` Con Kolivas
2010-08-23 7:15 ` Wu Fengguang
2010-08-23 7:15 ` Wu Fengguang
2010-08-24 0:00 ` KOSAKI Motohiro
2010-08-24 0:00 ` KOSAKI Motohiro
[not found] ` <201008241620.54048.kernel@kolivas.org>
[not found] ` <20100824071440.GA14598@localhost>
[not found] ` <201008251840.00532.kernel@kolivas.org>
2010-08-26 1:29 ` Wu Fengguang
2010-08-26 1:29 ` Wu Fengguang
2010-08-26 1:36 ` Neil Brown
2010-08-26 1:36 ` Neil Brown
2010-08-26 4:22 ` KOSAKI Motohiro
2010-08-26 4:22 ` KOSAKI Motohiro
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