linux-kernel - Re: [PATCH] kvm, mm: account kvm related kmem slabs to kmemcg

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Date:   Thu, 5 Oct 2017 23:40:04 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        Greg Thelen <gthelen@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>, x86@...nel.org,
        kvm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kvm, mm: account kvm related kmem slabs to kmemcg

On Thu, Oct 5, 2017 at 9:28 PM, Anshuman Khandual
<khandual@...ux.vnet.ibm.com> wrote:
> On 10/06/2017 06:37 AM, Shakeel Butt wrote:
>> The kvm slabs can consume a significant amount of system memory
>> and indeed in our production environment we have observed that
>> a lot of machines are spending significant amount of memory that
>> can not be left as system memory overhead. Also the allocations
>> from these slabs can be triggered directly by user space applications
>> which has access to kvm and thus a buggy application can leak
>> such memory. So, these caches should be accounted to kmemcg.
>
> But there may be other situations like this where user space can
> trigger allocation from various SLAB objects inside the kernel
> which are accounted as system memory. So how we draw the line
> which ones should be accounted for memcg. Just being curious.
>
Yes, there are indeed other slabs where user space can trigger
allocations. IMO selecting which kmem caches to account is kind of
workload and user specific decision. The ones I am converting are
selected based on the data gathered from our production environment.
However I think it would be useful in general.