From: Matthew Wilcox <willy@infradead.org>
To: Eric Dumazet <erdnetdev@gmail.com>
Cc: linux-mm@kvack.org, netdev@vger.kernel.org,
Dongli Zhang <dongli.zhang@oracle.com>,
Aruna Ramakrishna <aruna.ramakrishna@oracle.com>,
Bert Barbe <bert.barbe@oracle.com>,
Rama Nichanamatlu <rama.nichanamatlu@oracle.com>,
Venkat Venkatsubra <venkat.x.venkatsubra@oracle.com>,
Manjunath Patil <manjunath.b.patil@oracle.com>,
Joe Jin <joe.jin@oracle.com>, SRINIVAS <srinivas.eeda@oracle.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] page_frag: Recover from memory pressure
Date: Mon, 9 Nov 2020 14:32:49 +0000 [thread overview]
Message-ID: <20201109143249.GB17076@casper.infradead.org> (raw)
In-Reply-To: <20201105140224.GK17076@casper.infradead.org>
On Thu, Nov 05, 2020 at 02:02:24PM +0000, Matthew Wilcox wrote:
> On Thu, Nov 05, 2020 at 02:21:25PM +0100, Eric Dumazet wrote:
> > On 11/5/20 5:21 AM, Matthew Wilcox (Oracle) wrote:
> > > When the machine is under extreme memory pressure, the page_frag allocator
> > > signals this to the networking stack by marking allocations with the
> > > 'pfmemalloc' flag, which causes non-essential packets to be dropped.
> > > Unfortunately, even after the machine recovers from the low memory
> > > condition, the page continues to be used by the page_frag allocator,
> > > so all allocations from this page will continue to be dropped.
> > >
> > > Fix this by freeing and re-allocating the page instead of recycling it.
> > >
> > > Reported-by: Dongli Zhang <dongli.zhang@oracle.com>
> > > Cc: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
> > > Cc: Bert Barbe <bert.barbe@oracle.com>
> > > Cc: Rama Nichanamatlu <rama.nichanamatlu@oracle.com>
> > > Cc: Venkat Venkatsubra <venkat.x.venkatsubra@oracle.com>
> > > Cc: Manjunath Patil <manjunath.b.patil@oracle.com>
> > > Cc: Joe Jin <joe.jin@oracle.com>
> > > Cc: SRINIVAS <srinivas.eeda@oracle.com>
> > > Cc: stable@vger.kernel.org
> > > Fixes: 79930f5892e ("net: do not deplete pfmemalloc reserve")
> >
> > Your patch looks fine, although this Fixes: tag seems incorrect.
> >
> > 79930f5892e ("net: do not deplete pfmemalloc reserve") was propagating
> > the page pfmemalloc status into the skb, and seems correct to me.
> >
> > The bug was the page_frag_alloc() was keeping a problematic page for
> > an arbitrary period of time ?
>
> Isn't this the commit which unmasks the problem, though? I don't think
> it's the buggy commit, but if your tree doesn't have 79930f5892e, then
> you don't need this patch.
>
> Or are you saying the problem dates back all the way to
> c93bdd0e03e8 ("netvm: allow skb allocation to use PFMEMALLOC reserves")
>
> > > + if (nc->pfmemalloc) {
> >
> > if (unlikely(nc->pfmemalloc)) {
>
> ACK. Will make the change once we've settled on an appropriate Fixes tag.
Which commit should I claim this fixes?
next prev parent reply other threads:[~2020-11-09 14:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-05 4:21 [PATCH] page_frag: Recover from memory pressure Matthew Wilcox (Oracle)
2020-11-05 11:56 ` Vlastimil Babka
2020-11-05 12:05 ` Matthew Wilcox
2020-11-05 12:09 ` Vlastimil Babka
2020-11-05 13:21 ` Eric Dumazet
2020-11-05 14:02 ` Matthew Wilcox
2020-11-09 14:32 ` Matthew Wilcox [this message]
2020-11-09 14:37 ` Eric Dumazet
2020-11-15 6:47 ` Dongli Zhang
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