From: Nicolas Saenz Julienne <nsaenzju@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, frederic@kernel.org, tglx@linutronix.de,
mgorman@suse.de, linux-rt-users@vger.kernel.org, vbabka@suse.cz,
cl@linux.com, paulmck@kernel.org, willy@infradead.org
Subject: Re: [PATCH 2/2] mm/page_alloc: Add remote draining support to per-cpu lists
Date: Tue, 15 Feb 2022 09:47:35 +0100 [thread overview]
Message-ID: <2374bbca7651b671ec934fa5c630cbe3eed3b496.camel@redhat.com> (raw)
In-Reply-To: <YgKQfsznPUDN34un@fuller.cnet>
On Tue, 2022-02-08 at 12:47 -0300, Marcelo Tosatti wrote:
> > Changes since RFC:
> > - Avoid unnecessary spin_lock_irqsave/restore() in free_pcppages_bulk()
> > - Add more detail to commit and code comments.
> > - Use synchronize_rcu() instead of synchronize_rcu_expedited(), the RCU
> > documentation says to avoid it unless really justified. I don't think
> > it's justified here, if we can schedule and join works, waiting for
> > an RCU grace period is OK.
>
> https://patchwork.ozlabs.org/project/netdev/patch/1306228052.3026.16.camel@edumazet-laptop/
>
> Adding 100ms to direct reclaim path might be problematic. It will also
> slowdown kcompactd (note it'll call drain_all_pages for each zone).
I did some measurements on an idle machine, worst case was ~30ms. I agree that
might too much for direct reclaim, so I'll switch back to expedited and add a
comment.
> > - Avoid sparse warnings by using rcu_access_pointer() and
> > rcu_dereference_protected().
> >
> > include/linux/mmzone.h | 22 +++++-
> > mm/page_alloc.c | 155 ++++++++++++++++++++++++++---------------
> > mm/vmstat.c | 6 +-
> > 3 files changed, 120 insertions(+), 63 deletions(-)
> >
> > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> > index b4cb85d9c6e8..b0b593fd8e48 100644
> > --- a/include/linux/mmzone.h
> > +++ b/include/linux/mmzone.h
> > @@ -388,13 +388,31 @@ struct per_cpu_pages {
> > short expire; /* When 0, remote pagesets are drained */
> > #endif
> >
> > - struct pcplists *lp;
> > + /*
> > + * As a rule of thumb, any access to struct per_cpu_pages's 'lp' has
> > + * happen with the pagesets local_lock held and using
> > + * rcu_dereference_check(). If there is a need to modify both
> > + * 'lp->count' and 'lp->lists' in the same critical section 'pcp->lp'
> > + * can only be derefrenced once. See for example:
>
> Typo.
Noted.
Thanks!
--
Nicolás Sáenz
next prev parent reply other threads:[~2022-02-15 8:47 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-08 10:07 [PATCH 0/2] mm/page_alloc: Remote per-cpu lists drain support Nicolas Saenz Julienne
2022-02-08 10:07 ` [PATCH 1/2] mm/page_alloc: Access lists in 'struct per_cpu_pages' indirectly Nicolas Saenz Julienne
2022-03-03 14:33 ` Marcelo Tosatti
2022-02-08 10:07 ` [PATCH 2/2] mm/page_alloc: Add remote draining support to per-cpu lists Nicolas Saenz Julienne
2022-02-08 15:47 ` Marcelo Tosatti
2022-02-15 8:47 ` Nicolas Saenz Julienne [this message]
2022-02-15 17:32 ` Paul E. McKenney
2022-02-09 8:55 ` [PATCH 0/2] mm/page_alloc: Remote per-cpu lists drain support Xiongfeng Wang
2022-02-09 9:45 ` Nicolas Saenz Julienne
2022-02-09 11:26 ` Xiongfeng Wang
2022-02-09 11:36 ` Nicolas Saenz Julienne
2022-02-10 10:59 ` Xiongfeng Wang
2022-02-10 11:04 ` Nicolas Saenz Julienne
2022-03-03 11:45 ` Mel Gorman
2022-03-07 13:57 ` Nicolas Saenz Julienne
2022-03-10 16:31 ` Mel Gorman
2022-03-07 20:47 ` Marcelo Tosatti
2022-03-24 18:59 ` Nicolas Saenz Julienne
2022-03-25 10:48 ` Mel Gorman
2022-03-28 13:51 ` Nicolas Saenz Julienne
2022-03-29 9:45 ` Mel Gorman
2022-03-30 11:29 ` Nicolas Saenz Julienne
2022-03-31 15:24 ` Mel Gorman
2022-03-03 13:27 ` Vlastimil Babka
2022-03-03 14:10 ` Nicolas Saenz Julienne
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2374bbca7651b671ec934fa5c630cbe3eed3b496.camel@redhat.com \
--to=nsaenzju@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=frederic@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-rt-users@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mtosatti@redhat.com \
--cc=paulmck@kernel.org \
--cc=tglx@linutronix.de \
--cc=vbabka@suse.cz \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).