From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Andrew Morton <akpm@linux-foundation.org>,
Tim Chen <tim.c.chen@linux.intel.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andi Kleen <ak@linux.intel.com>,
Mel Gorman <mgorman@techsingularity.net>,
Vladimir Davydov <vdavydov@virtuozzo.com>,
Konstantin Khlebnikov <koct9i@gmail.com>
Subject: Re: [RFC PATCH 3/3] mm: increase scalability of global memory commitment accounting
Date: Fri, 12 Feb 2016 15:24:18 +0300 [thread overview]
Message-ID: <56BDCEF2.3030409@virtuozzo.com> (raw)
In-Reply-To: <20160211125103.8a4fb0ffed593938321755d2@linux-foundation.org>
On 02/11/2016 11:51 PM, Andrew Morton wrote:
> On Wed, 10 Feb 2016 16:24:16 -0800 Tim Chen <tim.c.chen@linux.intel.com> wrote:
>
>> On Wed, 2016-02-10 at 13:28 -0800, Andrew Morton wrote:
>>
>>>
>>> If a process is unmapping 4MB then it's pretty crazy for us to be
>>> hitting the percpu_counter 32 separate times for that single operation.
>>>
>>> Is there some way in which we can batch up the modifications within the
>>> caller and update the counter less frequently? Perhaps even in a
>>> single hit?
>>
>> I think the problem is the batch size is too small and we overflow
>> the local counter into the global counter for 4M allocations.
>
> That's one way of looking at the issue. The other way (which I point
> out above) is that we're calling vm_[un]_acct_memory too frequently
> when mapping/unmapping 4M segments.
>
We call it only once per mmap() or munmap(), so there is nothing to improve.
> Exactly which mmap.c callsite is causing this issue?
>
mmap_region() (or do_brk()) ->
security_vm_enough_memory() ->
__vm_enough_memory() ->
vm_acct_memory()
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prev parent reply other threads:[~2016-02-12 12:23 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-10 14:52 [PATCH 1/3] mm: move max_map_count bits into mm.h Andrey Ryabinin
2016-02-10 14:52 ` [PATCH 2/3] mm: dedupclicate memory overcommitment code Andrey Ryabinin
2016-02-10 14:52 ` [RFC PATCH 3/3] mm: increase scalability of global memory commitment accounting Andrey Ryabinin
2016-02-10 17:46 ` Konstantin Khlebnikov
2016-02-11 13:36 ` Andrey Ryabinin
2016-02-11 16:57 ` Tim Chen
2016-02-10 18:00 ` Tim Chen
2016-02-10 21:28 ` Andrew Morton
2016-02-11 0:24 ` Tim Chen
2016-02-11 13:54 ` Andrey Ryabinin
2016-02-11 18:20 ` Tim Chen
2016-02-11 19:45 ` Dave Hansen
2016-02-11 20:51 ` Andrew Morton
2016-02-11 21:18 ` Tim Chen
2016-02-12 12:24 ` Andrey Ryabinin [this message]
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