* Re: [withdrawn] zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch removed from -mm tree
[not found] <5513199f.t25SPuX5ULuM6JS8%akpm@linux-foundation.org>
@ 2015-03-26 0:27 ` Sergey Senozhatsky
2015-03-26 7:39 ` Minchan Kim
0 siblings, 1 reply; 4+ messages in thread
From: Sergey Senozhatsky @ 2015-03-26 0:27 UTC (permalink / raw)
To: minchan; +Cc: akpm, sergey.senozhatsky, ngupta, sfr, linux-kernel, linux-mm
On (03/25/15 13:25), akpm@linux-foundation.org wrote:
> The patch titled
> Subject: zsmalloc: remove extra cond_resched() in __zs_compact
> has been removed from the -mm tree. Its filename was
> zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch
>
> This patch was dropped because it was withdrawn
>
> ------------------------------------------------------
> From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Subject: zsmalloc: remove extra cond_resched() in __zs_compact
>
> Do not perform cond_resched() before the busy compaction loop in
> __zs_compact(), because this loop does it when needed.
>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Nitin Gupta <ngupta@vflare.org>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> mm/zsmalloc.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff -puN mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact mm/zsmalloc.c
> --- a/mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact
> +++ a/mm/zsmalloc.c
> @@ -1717,8 +1717,6 @@ static unsigned long __zs_compact(struct
> struct page *dst_page = NULL;
> unsigned long nr_total_migrated = 0;
>
> - cond_resched();
> -
> spin_lock(&class->lock);
> while ((src_page = isolate_source_page(class))) {
>
Hello,
Minchan, did I miss your NACK on this patch? or could you please ACK it?
-ss
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [withdrawn] zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch removed from -mm tree
2015-03-26 0:27 ` [withdrawn] zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch removed from -mm tree Sergey Senozhatsky
@ 2015-03-26 7:39 ` Minchan Kim
2015-03-26 8:13 ` Sergey Senozhatsky
0 siblings, 1 reply; 4+ messages in thread
From: Minchan Kim @ 2015-03-26 7:39 UTC (permalink / raw)
To: Sergey Senozhatsky
Cc: akpm, sergey.senozhatsky, ngupta, sfr, linux-kernel, linux-mm
Hello Sergey,
Sorry for slow response.
I am overwhelmed with too much to do. :(
On Thu, Mar 26, 2015 at 09:27:17AM +0900, Sergey Senozhatsky wrote:
> On (03/25/15 13:25), akpm@linux-foundation.org wrote:
> > The patch titled
> > Subject: zsmalloc: remove extra cond_resched() in __zs_compact
> > has been removed from the -mm tree. Its filename was
> > zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch
> >
> > This patch was dropped because it was withdrawn
> >
> > ------------------------------------------------------
> > From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> > Subject: zsmalloc: remove extra cond_resched() in __zs_compact
> >
> > Do not perform cond_resched() before the busy compaction loop in
> > __zs_compact(), because this loop does it when needed.
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> > Cc: Minchan Kim <minchan@kernel.org>
> > Cc: Nitin Gupta <ngupta@vflare.org>
> > Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> > ---
> >
> > mm/zsmalloc.c | 2 --
> > 1 file changed, 2 deletions(-)
> >
> > diff -puN mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact mm/zsmalloc.c
> > --- a/mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact
> > +++ a/mm/zsmalloc.c
> > @@ -1717,8 +1717,6 @@ static unsigned long __zs_compact(struct
> > struct page *dst_page = NULL;
> > unsigned long nr_total_migrated = 0;
> >
> > - cond_resched();
> > -
> > spin_lock(&class->lock);
> > while ((src_page = isolate_source_page(class))) {
> >
>
> Hello,
>
> Minchan, did I miss your NACK on this patch? or could you please ACK it?
I saw this patch yesterday night but didn't acked intentionally because
I was not sure and too tired to see the code so I postpone.
If we removed cond_resched out of outer loop(ie, your patch), we lose
the chance to reschedule if alloc_target_page fails(ie, there is no
zspage in ZS_ALMOST_FULL and ZS_ALMOST_EMPTY).
It might be not rare event if we does compation successfully for a
size_class. However, with next coming higher size_class for __zs_compact,
we will encounter cond_resched during compaction.
So, I am happy to ack. :)
Acked-by: Minchan Kim <minchan@kernel.org>
>
> -ss
--
Kind regards,
Minchan Kim
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [withdrawn] zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch removed from -mm tree
2015-03-26 7:39 ` Minchan Kim
@ 2015-03-26 8:13 ` Sergey Senozhatsky
2015-03-27 2:34 ` Minchan Kim
0 siblings, 1 reply; 4+ messages in thread
From: Sergey Senozhatsky @ 2015-03-26 8:13 UTC (permalink / raw)
To: Minchan Kim
Cc: Sergey Senozhatsky, akpm, sergey.senozhatsky, ngupta, sfr,
linux-kernel, linux-mm
On (03/26/15 16:39), Minchan Kim wrote:
> Hello Sergey,
>
> Sorry for slow response.
> I am overwhelmed with too much to do. :(
>
Hello,
sure, no problem.
> > > diff -puN mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact mm/zsmalloc.c
> > > --- a/mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact
> > > +++ a/mm/zsmalloc.c
> > > @@ -1717,8 +1717,6 @@ static unsigned long __zs_compact(struct
> > > struct page *dst_page = NULL;
> > > unsigned long nr_total_migrated = 0;
> > >
> > > - cond_resched();
> > > -
> > > spin_lock(&class->lock);
> > > while ((src_page = isolate_source_page(class))) {
>
> If we removed cond_resched out of outer loop(ie, your patch), we lose
> the chance to reschedule if alloc_target_page fails(ie, there is no
> zspage in ZS_ALMOST_FULL and ZS_ALMOST_EMPTY).
in outer loop we have preemption enabled and unlocked class. wouldn't that help?
(hm, UP system?)
> It might be not rare event if we does compation successfully for a
> size_class. However, with next coming higher size_class for __zs_compact,
> we will encounter cond_resched during compaction.
> So, I am happy to ack. :)
>
> Acked-by: Minchan Kim <minchan@kernel.org>
thanks!
-ss
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [withdrawn] zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch removed from -mm tree
2015-03-26 8:13 ` Sergey Senozhatsky
@ 2015-03-27 2:34 ` Minchan Kim
0 siblings, 0 replies; 4+ messages in thread
From: Minchan Kim @ 2015-03-27 2:34 UTC (permalink / raw)
To: Sergey Senozhatsky
Cc: akpm, sergey.senozhatsky, ngupta, sfr, linux-kernel, linux-mm
On Thu, Mar 26, 2015 at 05:13:13PM +0900, Sergey Senozhatsky wrote:
> On (03/26/15 16:39), Minchan Kim wrote:
> > Hello Sergey,
> >
> > Sorry for slow response.
> > I am overwhelmed with too much to do. :(
> >
>
> Hello,
> sure, no problem.
>
> > > > diff -puN mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact mm/zsmalloc.c
> > > > --- a/mm/zsmalloc.c~zsmalloc-remove-extra-cond_resched-in-__zs_compact
> > > > +++ a/mm/zsmalloc.c
> > > > @@ -1717,8 +1717,6 @@ static unsigned long __zs_compact(struct
> > > > struct page *dst_page = NULL;
> > > > unsigned long nr_total_migrated = 0;
> > > >
> > > > - cond_resched();
> > > > -
> > > > spin_lock(&class->lock);
> > > > while ((src_page = isolate_source_page(class))) {
>
> >
> > If we removed cond_resched out of outer loop(ie, your patch), we lose
> > the chance to reschedule if alloc_target_page fails(ie, there is no
> > zspage in ZS_ALMOST_FULL and ZS_ALMOST_EMPTY).
>
>
> in outer loop we have preemption enabled and unlocked class. wouldn't that help?
> (hm, UP system?)
It depends on preemption model. If you enable full preemption, you are right
but if you enable just voluntary preemption, cond_resched will help latency.
Thanks.
--
Kind regards,
Minchan Kim
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-03-26 0:27 ` [withdrawn] zsmalloc-remove-extra-cond_resched-in-__zs_compact.patch removed from -mm tree Sergey Senozhatsky
2015-03-26 7:39 ` Minchan Kim
2015-03-26 8:13 ` Sergey Senozhatsky
2015-03-27 2:34 ` Minchan Kim
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