From: Michal Hocko <mhocko@suse.com>
To: Rik van Riel <riel@surriel.com>
Cc: hughd@google.com, xuyu@linux.alibaba.com,
akpm@linux-foundation.org, mgorman@suse.de, aarcange@redhat.com,
willy@infradead.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com, linux-mm@kvack.org, vbabka@suse.cz
Subject: Re: [PATCH 1/2] mm,thp,shmem: limit shmem THP alloc gfp_mask
Date: Thu, 19 Nov 2020 10:37:03 +0100 [thread overview]
Message-ID: <20201119093703.GB12284@dhcp22.suse.cz> (raw)
In-Reply-To: <84effe90c3ee13fbfa6e732d2e3b3d9b557d1be1.camel@surriel.com>
On Fri 13-11-20 22:44:20, Rik van Riel wrote:
> On Thu, 2020-11-12 at 11:52 +0100, Michal Hocko wrote:
> > On Thu 05-11-20 14:15:07, Rik van Riel wrote:
> > >
> > > This patch applies the same configurated limitation of THPs to
> > > shmem
> > > hugepage allocations, to prevent that from happening.
> >
> > I believe you should also exaplain why we want to control defrag by
> > the
> > global knob while the enable logic is per mount.
>
> I added that to the changelog for the next version of
> the patches.
>
> > > This way a THP defrag setting of "never" or "defer+madvise" will
> > > result
> > > in quick allocation failures without direct reclaim when no 2MB
> > > free
> > > pages are available.
> > >
> > > With this patch applied, THP allocations for tmpfs will be a little
> > > more aggressive than today for files mmapped with MADV_HUGEPAGE,
> > > and a little less aggressive for files that are not mmapped or
> > > mapped without that flag.
> >
> > This begs some numbers. A little is rather bad unit of performance. I
> > do
> > agree that unifying those makes sense in general though.
>
> The aggressiveness is in changes to the gfp_mask, eg by
> adding __GFP_NORETRY. How that translates into THP
> allocation success rates is entirely dependent on the
> workload and on what else is in memory at the time.
Yes and that is why I would argue about consistency with THP rather than
put claims that hard to back by numbers.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-11-19 9:37 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-05 19:15 [PATCH 0/2] mm,thp,shm: limit shmem THP alloc gfp_mask Rik van Riel
2020-11-05 19:15 ` [PATCH 1/2] mm,thp,shmem: " Rik van Riel
2020-11-12 10:52 ` Michal Hocko
2020-11-14 3:44 ` Rik van Riel
2020-11-19 9:37 ` Michal Hocko [this message]
2020-11-05 19:15 ` [PATCH 2/2] mm,thp,shm: limit gfp mask to no more than specified Rik van Riel
2020-11-06 3:05 ` Hillf Danton
2020-11-06 17:53 ` Rik van Riel
2020-11-07 1:58 ` Hillf Danton
2020-11-12 11:22 ` Michal Hocko
2020-11-14 3:40 ` Rik van Riel
2020-11-19 9:38 ` Michal Hocko
2020-11-23 19:39 ` Rik van Riel
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