netdev - Re: [PATCH] net: add big honking pfmemalloc OOM warning

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Date:   Thu, 11 Apr 2019 03:26:30 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Juha-Matti Tilli <juha-matti.tilli@...eca.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Rafael Aquini <aquini@...hat.com>,
        Murphy Zhou <xzhou@...hat.com>,
        Yongcheng Yang <yoyang@...hat.com>,
        Jianhong Yin <jiyin@...hat.com>
Subject: Re: [PATCH] net: add big honking pfmemalloc OOM warning

On Wed, Apr 10, 2019 at 11:26 PM Juha-Matti Tilli
<juha-matti.tilli@...eca.com> wrote:
>
> On Wed, Apr 10, 2019 at 6:36 PM Eric Dumazet <edumazet@...gle.com> wrote:
> > Before diving into the details, can we first double check which exact
> > kernel version you are using ?
> >
> > In the past some pfmemalloc bugs have been solved, I do not want spend
> > time finding them a second time.
>
> Of course I can tell the kernel version.
>
> The NFS server is 3.10.0-862.14.4.el7.foreca.x86_64 where "foreca"
> means we've applied a custom Samsung SSD TRIM patch, nothing else
> different from regular CentOS / RHEL kernel.
>
> The NFS client is 3.10.0-957.5.1.el7.x86_64.
>
> The pfmemalloc problem happens at the server, not at the client.
>
> The exact patches in this kernel may be a bit complicated to
> determine, because RHEL apparently likes to maintain their own kernel
> version. They do not have the SNMP counter even, which is why I opened
> a bug report to RHEL Bugzilla. I have extracted source code, so if you
> can tell a list of git commit SHA1 hashes that could fix the issue, I
> can check manually whether they're there, and open bug reports to RHEL
> bugzilla to have them backported if not there.
>
> I at least see this in the exact kernel version I'm using:

Here (netdev/lkml) we deal with current kernels.

Chances are very high the bug(s) you are fighting was(were) already fixed.

Please repro the bug using latest David Miller net tree, otherwise we
will _not_ accept any patch.

Thank you

>
> static inline bool ixgbe_page_is_reserved(struct page *page)
> {
>         return (page_to_nid(page) != numa_mem_id()) || page_is_pfmemalloc(page);
> }
>
> ...so ixgbe shouldn't be reusing pfmemalloc pages.
>
> BR, Juha-Matti