From: Tejun Heo <tj@kernel.org>
To: Tahsin Erdogan <tahsin@google.com>
Cc: Michal Hocko <mhocko@kernel.org>,
Christoph Lameter <cl@linux.com>,
Andrew Morton <akpm@linux-foundation.org>,
Chris Wilson <chris@chris-wilson.co.uk>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Roman Pen <r.peniaev@gmail.com>,
Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
zijun_hu <zijun_hu@htc.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
David Rientjes <rientjes@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/3] percpu: improve allocation success rate for non-GFP_KERNEL callers
Date: Mon, 27 Feb 2017 15:29:06 -0500 [thread overview]
Message-ID: <20170227202906.GF8707@htj.duckdns.org> (raw)
In-Reply-To: <CAAeU0aORY=N0e0gMKu-CBAEF=HLuHUNV6KWy27th1rwuPMcTMg@mail.gmail.com>
Hello,
On Mon, Feb 27, 2017 at 12:27:08PM -0800, Tahsin Erdogan wrote:
> A better example is the call path below:
>
> pcpu_alloc+0x68f/0x710
> __alloc_percpu_gfp+0xd/0x10
> __percpu_counter_init+0x55/0xc0
> cfq_pd_alloc+0x3b2/0x4e0
> blkg_alloc+0x187/0x230
> blkg_create+0x489/0x670
> blkg_lookup_create+0x9a/0x230
> blkg_conf_prep+0x1fb/0x240
> __cfqg_set_weight_device.isra.105+0x5c/0x180
> cfq_set_weight_on_dfl+0x69/0xc0
> cgroup_file_write+0x39/0x1c0
> kernfs_fop_write+0x13f/0x1d0
> __vfs_write+0x23/0x120
> vfs_write+0xc2/0x1f0
> SyS_write+0x44/0xb0
> entry_SYSCALL_64_fastpath+0x18/0xad
>
> A failure in this call path gives grief to tools which are trying to
> configure io
> weights. We see occasional failures happen here shortly after reboots even
> when system is not under any memory pressure. Machines with a lot of cpus
> are obviously more vulnerable.
Ah, absolutely, that's a stupid failure but we should be able to fix
that by making the blkg functions take gfp mask and allocate
accordingly, right? It'll probably take preallocation tricks because
of locking but should be doable.
Thanks.
--
tejun
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next prev parent reply other threads:[~2017-02-27 20:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-25 21:00 [PATCH " Tahsin Erdogan
2017-02-25 23:54 ` kbuild test robot
2017-02-26 0:48 ` kbuild test robot
2017-02-26 4:38 ` [PATCH v2 " Tahsin Erdogan
2017-02-27 9:52 ` Michal Hocko
2017-02-27 13:00 ` Tahsin Erdogan
2017-02-27 15:25 ` Michal Hocko
2017-02-27 17:01 ` Tahsin Erdogan
2017-02-27 17:07 ` Michal Hocko
2017-02-27 17:14 ` Michal Hocko
2017-02-27 19:32 ` Tahsin Erdogan
2017-02-27 19:47 ` Michal Hocko
2017-02-27 19:51 ` Tejun Heo
2017-02-27 20:27 ` Tahsin Erdogan
2017-02-27 20:29 ` Tejun Heo [this message]
2017-02-27 20:37 ` Tahsin Erdogan
2017-02-27 20:45 ` Tejun Heo
2017-02-27 21:12 ` Tahsin Erdogan
2017-02-27 21:28 ` Tejun Heo
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