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* [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator
@ 2021-07-05 17:05 Uladzislau Rezki (Sony)
  2021-07-05 17:05 ` [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check Uladzislau Rezki (Sony)
                   ` (2 more replies)
  0 siblings, 3 replies; 9+ messages in thread
From: Uladzislau Rezki (Sony) @ 2021-07-05 17:05 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-mm, LKML, Mel Gorman, Christoph Hellwig, Matthew Wilcox,
	Nicholas Piggin, Uladzislau Rezki, Hillf Danton, Michal Hocko,
	Oleksiy Avramchenko, Steven Rostedt

In case of simultaneous vmalloc allocations, for example it is 1GB and
12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT
kernel.

<snip>
[   62.512621] RIP: 0010:__alloc_pages_bulk+0xa9f/0xbb0
[   62.512628] Code: ff 8b 44 24 48 44 29 f8 83 f8 01 0f 84 ea fe ff ff e9 07 f6 ff ff 48 8b 44 24 60 48 89 28 e9 00 f9 ff ff fb 66 0f 1f 44 00 00 <e9> e8 fd ff ff 65 48 01 51 10 e9 3e fe ff ff 48 8b 44 24 78 4d 89
[   62.512629] RSP: 0018:ffffa7bfc29ffd20 EFLAGS: 00000206
[   62.512631] RAX: 0000000000000200 RBX: ffffcd5405421888 RCX: ffff8c36ffdeb928
[   62.512632] RDX: 0000000000040000 RSI: ffffa896f06b2ff8 RDI: ffffcd5405421880
[   62.512633] RBP: ffffcd5405421880 R08: 000000000000007d R09: ffffffffffffffff
[   62.512634] R10: ffffffff9d63c084 R11: 00000000ffffffff R12: ffff8c373ffaeb80
[   62.512635] R13: ffff8c36ffdf65f8 R14: ffff8c373ffaeb80 R15: 0000000000040000
[   62.512637] FS:  0000000000000000(0000) GS:ffff8c36ffdc0000(0000) knlGS:0000000000000000
[   62.512638] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   62.512639] CR2: 000055c8e2fe8610 CR3: 0000000c13e10000 CR4: 00000000000006e0
[   62.512641] Call Trace:
[   62.512646]  __vmalloc_node_range+0x11c/0x2d0
[   62.512649]  ? full_fit_alloc_test+0x140/0x140 [test_vmalloc]
[   62.512654]  __vmalloc_node+0x4b/0x70
[   62.512656]  ? fix_size_alloc_test+0x44/0x60 [test_vmalloc]
[   62.512659]  fix_size_alloc_test+0x44/0x60 [test_vmalloc]
[   62.512662]  test_func+0xe7/0x1f0 [test_vmalloc]
[   62.512666]  ? fix_align_alloc_test+0x50/0x50 [test_vmalloc]
[   62.512668]  kthread+0x11a/0x140
[   62.512671]  ? set_kthread_struct+0x40/0x40
[   62.512672]  ret_from_fork+0x22/0x30
<snip>

To address this issue invoke a bulk-allocator many times until all pages
are obtained, i.e. do batched page requests adding cond_resched() meanwhile
to reschedule. Batched value is hard-coded and is 100 pages per call.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 mm/vmalloc.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index aaad569e8963..5297958ac7c5 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2785,10 +2785,32 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 	 * to fails, fallback to a single page allocator that is
 	 * more permissive.
 	 */
-	if (!order)
-		nr_allocated = alloc_pages_bulk_array_node(
-			gfp, nid, nr_pages, pages);
-	else
+	if (!order) {
+		while (nr_allocated < nr_pages) {
+			int nr, nr_pages_request;
+
+			/*
+			 * A maximum allowed request is hard-coded and is 100
+			 * pages per call. That is done in order to prevent a
+			 * long preemption off scenario in the bulk-allocator
+			 * so the range is [1:100].
+			 */
+			nr_pages_request = min(100, (int)(nr_pages - nr_allocated));
+
+			nr = alloc_pages_bulk_array_node(gfp, nid,
+				nr_pages_request, pages + nr_allocated);
+
+			nr_allocated += nr;
+			cond_resched();
+
+			/*
+			 * If zero or pages were obtained partly,
+			 * fallback to a single page allocator.
+			 */
+			if (nr != nr_pages_request)
+				break;
+		}
+	} else
 		/*
 		 * Compound pages required for remap_vmalloc_page if
 		 * high-order pages.
-- 
2.20.1


^ permalink raw reply	[flat|nested] 9+ messages in thread

* [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check
  2021-07-05 17:05 [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Uladzislau Rezki (Sony)
@ 2021-07-05 17:05 ` Uladzislau Rezki (Sony)
  2021-07-07  8:51   ` Michal Hocko
  2021-07-06 20:26 ` [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Andrew Morton
  2021-07-07  8:50 ` Michal Hocko
  2 siblings, 1 reply; 9+ messages in thread
From: Uladzislau Rezki (Sony) @ 2021-07-05 17:05 UTC (permalink / raw)
  To: Andrew Morton
  Cc: linux-mm, LKML, Mel Gorman, Christoph Hellwig, Matthew Wilcox,
	Nicholas Piggin, Uladzislau Rezki, Hillf Danton, Michal Hocko,
	Oleksiy Avramchenko, Steven Rostedt

Get rid of gfpflags_allow_blocking() check from the vmalloc() path
as it is supposed to be sleepable anyway. Thus remove it from the
alloc_vmap_area() as well as from the vm_area_alloc_pages().

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 mm/vmalloc.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5297958ac7c5..93a9cbdba905 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1479,6 +1479,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 				int node, gfp_t gfp_mask)
 {
 	struct vmap_area *va;
+	unsigned long freed;
 	unsigned long addr;
 	int purged = 0;
 	int ret;
@@ -1542,13 +1543,12 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 		goto retry;
 	}
 
-	if (gfpflags_allow_blocking(gfp_mask)) {
-		unsigned long freed = 0;
-		blocking_notifier_call_chain(&vmap_notify_list, 0, &freed);
-		if (freed > 0) {
-			purged = 0;
-			goto retry;
-		}
+	freed = 0;
+	blocking_notifier_call_chain(&vmap_notify_list, 0, &freed);
+
+	if (freed > 0) {
+		purged = 0;
+		goto retry;
 	}
 
 	if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())
@@ -2834,9 +2834,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
 		for (i = 0; i < (1U << order); i++)
 			pages[nr_allocated + i] = page + i;
 
-		if (gfpflags_allow_blocking(gfp))
-			cond_resched();
-
+		cond_resched();
 		nr_allocated += 1U << order;
 	}
 
-- 
2.20.1


^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator
  2021-07-05 17:05 [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Uladzislau Rezki (Sony)
  2021-07-05 17:05 ` [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check Uladzislau Rezki (Sony)
@ 2021-07-06 20:26 ` Andrew Morton
  2021-07-07  8:42   ` Michal Hocko
  2021-07-07 14:49   ` Uladzislau Rezki
  2021-07-07  8:50 ` Michal Hocko
  2 siblings, 2 replies; 9+ messages in thread
From: Andrew Morton @ 2021-07-06 20:26 UTC (permalink / raw)
  To: Uladzislau Rezki (Sony)
  Cc: linux-mm, LKML, Mel Gorman, Christoph Hellwig, Matthew Wilcox,
	Nicholas Piggin, Hillf Danton, Michal Hocko, Oleksiy Avramchenko,
	Steven Rostedt

On Mon,  5 Jul 2021 19:05:36 +0200 "Uladzislau Rezki (Sony)" <urezki@gmail.com> wrote:

> In case of simultaneous vmalloc allocations, for example it is 1GB and
> 12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT
> kernel.
> 
> <snip>
> ...
>
> are obtained, i.e. do batched page requests adding cond_resched() meanwhile
> to reschedule. Batched value is hard-coded and is 100 pages per call.
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Can we please have a Fixes: for this?

Is this fix important enough for 4.14-rcx?  I think so...

> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2785,10 +2785,32 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>  	 * to fails, fallback to a single page allocator that is
>  	 * more permissive.
>  	 */
> -	if (!order)
> -		nr_allocated = alloc_pages_bulk_array_node(
> -			gfp, nid, nr_pages, pages);
> -	else
> +	if (!order) {
> +		while (nr_allocated < nr_pages) {
> +			int nr, nr_pages_request;
> +
> +			/*
> +			 * A maximum allowed request is hard-coded and is 100
> +			 * pages per call. That is done in order to prevent a
> +			 * long preemption off scenario in the bulk-allocator
> +			 * so the range is [1:100].
> +			 */
> +			nr_pages_request = min(100, (int)(nr_pages - nr_allocated));

Yes, they types are all over the place.

nr_pages: unsigned long
nr_allocated: unsigned int
nr, nr_pages_request: int

Can we please choose the most appropriate type and use that
consistently?



^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator
  2021-07-06 20:26 ` [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Andrew Morton
@ 2021-07-07  8:42   ` Michal Hocko
  2021-07-07 14:47     ` Uladzislau Rezki
  2021-07-07 14:49   ` Uladzislau Rezki
  1 sibling, 1 reply; 9+ messages in thread
From: Michal Hocko @ 2021-07-07  8:42 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Uladzislau Rezki (Sony),
	linux-mm, LKML, Mel Gorman, Christoph Hellwig, Matthew Wilcox,
	Nicholas Piggin, Hillf Danton, Oleksiy Avramchenko,
	Steven Rostedt

On Tue 06-07-21 13:26:53, Andrew Morton wrote:
> On Mon,  5 Jul 2021 19:05:36 +0200 "Uladzislau Rezki (Sony)" <urezki@gmail.com> wrote:
> 
> > In case of simultaneous vmalloc allocations, for example it is 1GB and
> > 12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT
> > kernel.
> > 
> > <snip>
> > ...
> >
> > are obtained, i.e. do batched page requests adding cond_resched() meanwhile
> > to reschedule. Batched value is hard-coded and is 100 pages per call.
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> 
> Can we please have a Fixes: for this?

Is this a fix for any actual real life problem? I mean allocating 1GB of
vmalloc space back and forth sounds like a stretch to me.
 
> Is this fix important enough for 4.14-rcx?  I think so...

I do not think so. This is an improvement so that vmalloc behaves more
sanely for those abusers...
-- 
Michal Hocko
SUSE Labs

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator
  2021-07-05 17:05 [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Uladzislau Rezki (Sony)
  2021-07-05 17:05 ` [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check Uladzislau Rezki (Sony)
  2021-07-06 20:26 ` [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Andrew Morton
@ 2021-07-07  8:50 ` Michal Hocko
  2 siblings, 0 replies; 9+ messages in thread
From: Michal Hocko @ 2021-07-07  8:50 UTC (permalink / raw)
  To: Uladzislau Rezki (Sony)
  Cc: Andrew Morton, linux-mm, LKML, Mel Gorman, Christoph Hellwig,
	Matthew Wilcox, Nicholas Piggin, Hillf Danton,
	Oleksiy Avramchenko, Steven Rostedt

On Mon 05-07-21 19:05:36, Uladzislau Rezki (Sony) wrote:
> In case of simultaneous vmalloc allocations, for example it is 1GB and
> 12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT
> kernel.
> 
> <snip>
> [   62.512621] RIP: 0010:__alloc_pages_bulk+0xa9f/0xbb0
> [   62.512628] Code: ff 8b 44 24 48 44 29 f8 83 f8 01 0f 84 ea fe ff ff e9 07 f6 ff ff 48 8b 44 24 60 48 89 28 e9 00 f9 ff ff fb 66 0f 1f 44 00 00 <e9> e8 fd ff ff 65 48 01 51 10 e9 3e fe ff ff 48 8b 44 24 78 4d 89
> [   62.512629] RSP: 0018:ffffa7bfc29ffd20 EFLAGS: 00000206
> [   62.512631] RAX: 0000000000000200 RBX: ffffcd5405421888 RCX: ffff8c36ffdeb928
> [   62.512632] RDX: 0000000000040000 RSI: ffffa896f06b2ff8 RDI: ffffcd5405421880
> [   62.512633] RBP: ffffcd5405421880 R08: 000000000000007d R09: ffffffffffffffff
> [   62.512634] R10: ffffffff9d63c084 R11: 00000000ffffffff R12: ffff8c373ffaeb80
> [   62.512635] R13: ffff8c36ffdf65f8 R14: ffff8c373ffaeb80 R15: 0000000000040000
> [   62.512637] FS:  0000000000000000(0000) GS:ffff8c36ffdc0000(0000) knlGS:0000000000000000
> [   62.512638] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   62.512639] CR2: 000055c8e2fe8610 CR3: 0000000c13e10000 CR4: 00000000000006e0
> [   62.512641] Call Trace:
> [   62.512646]  __vmalloc_node_range+0x11c/0x2d0
> [   62.512649]  ? full_fit_alloc_test+0x140/0x140 [test_vmalloc]
> [   62.512654]  __vmalloc_node+0x4b/0x70
> [   62.512656]  ? fix_size_alloc_test+0x44/0x60 [test_vmalloc]
> [   62.512659]  fix_size_alloc_test+0x44/0x60 [test_vmalloc]
> [   62.512662]  test_func+0xe7/0x1f0 [test_vmalloc]
> [   62.512666]  ? fix_align_alloc_test+0x50/0x50 [test_vmalloc]
> [   62.512668]  kthread+0x11a/0x140
> [   62.512671]  ? set_kthread_struct+0x40/0x40
> [   62.512672]  ret_from_fork+0x22/0x30
> <snip>
> 
> To address this issue invoke a bulk-allocator many times until all pages
> are obtained, i.e. do batched page requests adding cond_resched() meanwhile
> to reschedule. Batched value is hard-coded and is 100 pages per call.

Yes, this makes perfect sense to me. I would just be more explicit that
this is an artificially created problem likely not being a problem at
the moment but why not to prepare for a future.

> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Acked-by: Michal Hocko <mhocko@suse.com>


Thanks!
> ---
>  mm/vmalloc.c | 30 ++++++++++++++++++++++++++----
>  1 file changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index aaad569e8963..5297958ac7c5 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2785,10 +2785,32 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>  	 * to fails, fallback to a single page allocator that is
>  	 * more permissive.
>  	 */
> -	if (!order)
> -		nr_allocated = alloc_pages_bulk_array_node(
> -			gfp, nid, nr_pages, pages);
> -	else
> +	if (!order) {
> +		while (nr_allocated < nr_pages) {
> +			int nr, nr_pages_request;
> +
> +			/*
> +			 * A maximum allowed request is hard-coded and is 100
> +			 * pages per call. That is done in order to prevent a
> +			 * long preemption off scenario in the bulk-allocator
> +			 * so the range is [1:100].
> +			 */
> +			nr_pages_request = min(100, (int)(nr_pages - nr_allocated));
> +
> +			nr = alloc_pages_bulk_array_node(gfp, nid,
> +				nr_pages_request, pages + nr_allocated);
> +
> +			nr_allocated += nr;
> +			cond_resched();
> +
> +			/*
> +			 * If zero or pages were obtained partly,
> +			 * fallback to a single page allocator.
> +			 */
> +			if (nr != nr_pages_request)
> +				break;
> +		}
> +	} else
>  		/*
>  		 * Compound pages required for remap_vmalloc_page if
>  		 * high-order pages.
> -- 
> 2.20.1

-- 
Michal Hocko
SUSE Labs

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check
  2021-07-05 17:05 ` [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check Uladzislau Rezki (Sony)
@ 2021-07-07  8:51   ` Michal Hocko
  2021-07-07 14:43     ` Uladzislau Rezki
  0 siblings, 1 reply; 9+ messages in thread
From: Michal Hocko @ 2021-07-07  8:51 UTC (permalink / raw)
  To: Uladzislau Rezki (Sony)
  Cc: Andrew Morton, linux-mm, LKML, Mel Gorman, Christoph Hellwig,
	Matthew Wilcox, Nicholas Piggin, Hillf Danton,
	Oleksiy Avramchenko, Steven Rostedt

On Mon 05-07-21 19:05:37, Uladzislau Rezki (Sony) wrote:
> Get rid of gfpflags_allow_blocking() check from the vmalloc() path
> as it is supposed to be sleepable anyway. Thus remove it from the
> alloc_vmap_area() as well as from the vm_area_alloc_pages().
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  mm/vmalloc.c | 18 ++++++++----------
>  1 file changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 5297958ac7c5..93a9cbdba905 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1479,6 +1479,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  				int node, gfp_t gfp_mask)
>  {
>  	struct vmap_area *va;
> +	unsigned long freed;
>  	unsigned long addr;
>  	int purged = 0;
>  	int ret;
> @@ -1542,13 +1543,12 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>  		goto retry;
>  	}
>  
> -	if (gfpflags_allow_blocking(gfp_mask)) {
> -		unsigned long freed = 0;
> -		blocking_notifier_call_chain(&vmap_notify_list, 0, &freed);
> -		if (freed > 0) {
> -			purged = 0;
> -			goto retry;
> -		}
> +	freed = 0;
> +	blocking_notifier_call_chain(&vmap_notify_list, 0, &freed);
> +
> +	if (freed > 0) {
> +		purged = 0;
> +		goto retry;
>  	}
>  
>  	if (!(gfp_mask & __GFP_NOWARN) && printk_ratelimit())
> @@ -2834,9 +2834,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>  		for (i = 0; i < (1U << order); i++)
>  			pages[nr_allocated + i] = page + i;
>  
> -		if (gfpflags_allow_blocking(gfp))
> -			cond_resched();
> -
> +		cond_resched();
>  		nr_allocated += 1U << order;
>  	}
>  
> -- 
> 2.20.1

-- 
Michal Hocko
SUSE Labs

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check
  2021-07-07  8:51   ` Michal Hocko
@ 2021-07-07 14:43     ` Uladzislau Rezki
  0 siblings, 0 replies; 9+ messages in thread
From: Uladzislau Rezki @ 2021-07-07 14:43 UTC (permalink / raw)
  To: Michal Hocko
  Cc: Uladzislau Rezki (Sony),
	Andrew Morton, linux-mm, LKML, Mel Gorman, Christoph Hellwig,
	Matthew Wilcox, Nicholas Piggin, Hillf Danton,
	Oleksiy Avramchenko, Steven Rostedt

On Wed, Jul 07, 2021 at 10:51:22AM +0200, Michal Hocko wrote:
> On Mon 05-07-21 19:05:37, Uladzislau Rezki (Sony) wrote:
> > Get rid of gfpflags_allow_blocking() check from the vmalloc() path
> > as it is supposed to be sleepable anyway. Thus remove it from the
> > alloc_vmap_area() as well as from the vm_area_alloc_pages().
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> 
> Acked-by: Michal Hocko <mhocko@suse.com>
> 

Thanks!

--
Vlad Rezki

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator
  2021-07-07  8:42   ` Michal Hocko
@ 2021-07-07 14:47     ` Uladzislau Rezki
  0 siblings, 0 replies; 9+ messages in thread
From: Uladzislau Rezki @ 2021-07-07 14:47 UTC (permalink / raw)
  To: Andrew Morton, Michal Hocko
  Cc: Andrew Morton, Uladzislau Rezki (Sony),
	linux-mm, LKML, Mel Gorman, Christoph Hellwig, Matthew Wilcox,
	Nicholas Piggin, Hillf Danton, Oleksiy Avramchenko,
	Steven Rostedt

On Wed, Jul 07, 2021 at 10:42:29AM +0200, Michal Hocko wrote:
> On Tue 06-07-21 13:26:53, Andrew Morton wrote:
> > On Mon,  5 Jul 2021 19:05:36 +0200 "Uladzislau Rezki (Sony)" <urezki@gmail.com> wrote:
> > 
> > > In case of simultaneous vmalloc allocations, for example it is 1GB and
> > > 12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT
> > > kernel.
> > > 
> > > <snip>
> > > ...
> > >
> > > are obtained, i.e. do batched page requests adding cond_resched() meanwhile
> > > to reschedule. Batched value is hard-coded and is 100 pages per call.
> > > 
> > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> > 
> > Can we please have a Fixes: for this?
> 
> Is this a fix for any actual real life problem? I mean allocating 1GB of
> vmalloc space back and forth sounds like a stretch to me.
>  
It is not a real scenario. I simulated it by the stress-suite tests. So the
Fixes tag is not needed, IMHO.

> > Is this fix important enough for 4.14-rcx?  I think so...
> 
> I do not think so. This is an improvement so that vmalloc behaves more
> sanely for those abusers...
>
A bulk-allocator has recently been introduced, so 4.x does not have it,
i.e. this change is not applicable and 4.x kernel does not suffer from
it.

--
Vlad Rezki

^ permalink raw reply	[flat|nested] 9+ messages in thread

* Re: [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator
  2021-07-06 20:26 ` [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Andrew Morton
  2021-07-07  8:42   ` Michal Hocko
@ 2021-07-07 14:49   ` Uladzislau Rezki
  1 sibling, 0 replies; 9+ messages in thread
From: Uladzislau Rezki @ 2021-07-07 14:49 UTC (permalink / raw)
  To: Andrew Morton
  Cc: Uladzislau Rezki (Sony),
	linux-mm, LKML, Mel Gorman, Christoph Hellwig, Matthew Wilcox,
	Nicholas Piggin, Hillf Danton, Michal Hocko, Oleksiy Avramchenko,
	Steven Rostedt

On Tue, Jul 06, 2021 at 01:26:53PM -0700, Andrew Morton wrote:
> On Mon,  5 Jul 2021 19:05:36 +0200 "Uladzislau Rezki (Sony)" <urezki@gmail.com> wrote:
> 
> > In case of simultaneous vmalloc allocations, for example it is 1GB and
> > 12 CPUs my system is able to hit "BUG: soft lockup" for !CONFIG_PREEMPT
> > kernel.
> > 
> > <snip>
> > ...
> >
> > are obtained, i.e. do batched page requests adding cond_resched() meanwhile
> > to reschedule. Batched value is hard-coded and is 100 pages per call.
> > 
> > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
> 
> Can we please have a Fixes: for this?
> 
> Is this fix important enough for 4.14-rcx?  I think so...
> 
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2785,10 +2785,32 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> >  	 * to fails, fallback to a single page allocator that is
> >  	 * more permissive.
> >  	 */
> > -	if (!order)
> > -		nr_allocated = alloc_pages_bulk_array_node(
> > -			gfp, nid, nr_pages, pages);
> > -	else
> > +	if (!order) {
> > +		while (nr_allocated < nr_pages) {
> > +			int nr, nr_pages_request;
> > +
> > +			/*
> > +			 * A maximum allowed request is hard-coded and is 100
> > +			 * pages per call. That is done in order to prevent a
> > +			 * long preemption off scenario in the bulk-allocator
> > +			 * so the range is [1:100].
> > +			 */
> > +			nr_pages_request = min(100, (int)(nr_pages - nr_allocated));
> 
> Yes, they types are all over the place.
> 
> nr_pages: unsigned long
> nr_allocated: unsigned int
> nr, nr_pages_request: int
> 
> Can we please choose the most appropriate type and use that
> consistently?
> 
Let me think over it to see what i can do.

--
Vlad Rezki

^ permalink raw reply	[flat|nested] 9+ messages in thread

end of thread, other threads:[~2021-07-07 14:51 UTC | newest]

Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-07-05 17:05 [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Uladzislau Rezki (Sony)
2021-07-05 17:05 ` [PATCH v2 2/2] mm/vmalloc: Remove gfpflags_allow_blocking() check Uladzislau Rezki (Sony)
2021-07-07  8:51   ` Michal Hocko
2021-07-07 14:43     ` Uladzislau Rezki
2021-07-06 20:26 ` [PATCH v2 1/2] mm/vmalloc: Use batched page requests in bulk-allocator Andrew Morton
2021-07-07  8:42   ` Michal Hocko
2021-07-07 14:47     ` Uladzislau Rezki
2021-07-07 14:49   ` Uladzislau Rezki
2021-07-07  8:50 ` Michal Hocko

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