From: Thomas Garnier <thgarnie@google.com>
To: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>,
Pekka Enberg <penberg@kernel.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Greg Thelen <gthelen@google.com>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v2] memcg: Prevent memcg caches to be both OFF_SLAB & OBJFREELIST_SLAB
Date: Mon, 7 Nov 2016 11:52:46 -0800 [thread overview]
Message-ID: <CAJcbSZE+TsP4i7GisocejQMwbVYv+AH8GY1JA8+o4Zt8ropCKw@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.20.1611071324380.19249@east.gentwo.org>
On Mon, Nov 7, 2016 at 11:28 AM, Christoph Lameter <cl@linux.com> wrote:
> On Mon, 7 Nov 2016, Thomas Garnier wrote:
>
>> I am not sure that is possible. kmem_cache_create currently check for
>> possible alias, I assume that it goes against what memcg tries to do.
>
> What does aliasing have to do with this? The aliases must have the same
> flags otherwise the caches would not have been merged.
>
I assume there might be cases where the parent cache and the new memcg
cache are compatible for merge (same flags and size). We can bypass
that by adding SLAB_NEVER_MERGE but I am not sure what is the
consequence of that.
>> Separate the changes in two patches might make sense:
>>
>> 1) Fix the original bug by masking the flags passed to create_cache
>> 2) Add flags check in kmem_cache_create.
>>
>> Does it make sense?
>
> Sure.
>
Great, I will send both patches.
>> > I also want to make sure that there are no other callers that specify
>> > extraneou flags while we are at it.
>> I will review as many as I can but we might run into surprises (quick
>> boot on defconfig didn't show anything). That's why having two
>> different patches might be useful.
>
> These surprises can be caught later ... Just make sure that the core works
> fine with this. You cannot audit all drivers.
>
Okay, I will.
--
Thomas
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prev parent reply other threads:[~2016-11-07 19:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-31 18:36 Thomas Garnier
2016-10-31 23:38 ` David Rientjes
2016-11-02 15:59 ` Thomas Garnier
2016-11-03 0:46 ` David Rientjes
2016-11-03 20:33 ` Christoph Lameter
2016-11-07 18:52 ` Thomas Garnier
2016-11-07 19:28 ` Christoph Lameter
2016-11-07 19:52 ` Thomas Garnier [this message]
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