From: Alexander Duyck <alexander.duyck@gmail.com>
To: Wei Yang <richard.weiyang@linux.alibaba.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm/page_reporting: the "page" must not be the list head
Date: Tue, 18 Aug 2020 07:58:14 -0700 [thread overview]
Message-ID: <CAKgT0UdiRw4WMe8RxOZ3A6fcQJ9Tp7BAWBbuYkje7YWiT0cVOA@mail.gmail.com> (raw)
In-Reply-To: <20200818032217.GA31960@L-31X9LVDL-1304.local>
On Mon, Aug 17, 2020 at 8:22 PM Wei Yang
<richard.weiyang@linux.alibaba.com> wrote:
>
> On Mon, Aug 17, 2020 at 09:05:32AM -0700, Alexander Duyck wrote:
> >
> >
> >On 8/17/2020 2:35 AM, David Hildenbrand wrote:
> >> On 17.08.20 10:48, Wei Yang wrote:
> >> > If "page" is the list head, list_for_each_entry_safe() would stop
> >> > iteration.
> >> >
> >> > Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
> >> > ---
> >> > mm/page_reporting.c | 2 +-
> >> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >> >
> >> > diff --git a/mm/page_reporting.c b/mm/page_reporting.c
> >> > index 3bbd471cfc81..aaaa3605123d 100644
> >> > --- a/mm/page_reporting.c
> >> > +++ b/mm/page_reporting.c
> >> > @@ -178,7 +178,7 @@ page_reporting_cycle(struct page_reporting_dev_info *prdev, struct zone *zone,
> >> > * the new head of the free list before we release the
> >> > * zone lock.
> >> > */
> >> > - if (&page->lru != list && !list_is_first(&page->lru, list))
> >> > + if (!list_is_first(&page->lru, list))
> >> > list_rotate_to_front(&page->lru, list);
> >> > /* release lock before waiting on report processing */
> >> >
> >>
> >> Is this a fix or a cleanup? If it's a fix, can this be reproduced easily
> >> and what ere the effects?
> >>
> >
> >This should be a clean-up. Since the &page->lru != list will always be true.
> >
> >If I recall at some point the that was a check for &next->lru != list but I
> >think I pulled out an additional conditional check somewhere so that we just
> >go through the start of the loop again and iterate over reported pages until
> >we are guaranteed to have a non-reported page to rotate to the top of the
> >list with the general idea being that we wanted the allocator to pull
> >non-reported pages before reported pages.
>
> Hi, Alexander,
>
> I see you mentioned in the changelog, this change "mm/page_reporting: rotate
> reported pages to the tail of the list" brings some performance gain.
>
> Would you mind sharing more test detail? I would like to have a try at my
> side.
>
> Thanks :-)
I seem to recall my default test for most of this was the page_fault1
test from the will-it-scale suite of tests. Basically I was running
that while leaving page reporting enabled. However I don't know how
much visibility you would have into the performance impact as I seem
to recall I had to modify the frequency of scheduling for the
reporting polling task in order to see much of an impact.
Thanks.
- Alex
next prev parent reply other threads:[~2020-08-18 14:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-17 8:48 [PATCH] mm/page_reporting: the "page" must not be the list head Wei Yang
2020-08-17 9:35 ` David Hildenbrand
2020-08-17 16:05 ` Alexander Duyck
2020-08-17 17:07 ` David Hildenbrand
2020-08-18 3:05 ` Wei Yang
2020-08-18 7:23 ` David Hildenbrand
2020-08-18 8:41 ` Wei Yang
2020-08-18 3:22 ` Wei Yang
2020-08-18 14:58 ` Alexander Duyck [this message]
2020-08-18 3:03 ` Wei Yang
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