From: Vlastimil Babka <vbabka@suse.cz>
To: David Hildenbrand <david@redhat.com>,
ultrachin@163.com, akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Cc: brookxu.cn@gmail.com, chen xiaoguang <xiaoggchen@tencent.com>,
zeng jingxiang <linuszeng@tencent.com>,
lu yihui <yihuilu@tencent.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>
Subject: Re: [PATCH] mm: Free per cpu pages async to shorten program exit time
Date: Fri, 8 Oct 2021 14:38:15 +0200 [thread overview]
Message-ID: <8f30837b-5186-e836-21bc-9964456400c1@suse.cz> (raw)
In-Reply-To: <d71e6021-777b-3ca9-b08f-64fe7ff51e08@redhat.com>
On 10/8/21 10:17, David Hildenbrand wrote:
> On 08.10.21 08:39, ultrachin@163.com wrote:
>> From: chen xiaoguang <xiaoggchen@tencent.com>
>>
>> The exit time is long when program allocated big memory and
>> the most time consuming part is free memory which takes 99.9%
>> of the total exit time. By using async free we can save 25% of
>> exit time.
>>
>> Signed-off-by: chen xiaoguang <xiaoggchen@tencent.com>
>> Signed-off-by: zeng jingxiang <linuszeng@tencent.com>
>> Signed-off-by: lu yihui <yihuilu@tencent.com>
>
> I recently discussed with Claudio if it would be possible to tear down the
> process MM deferred, because for some use cases (secure/encrypted
> virtualization, very large mmaps) tearing down the page tables is already
> the much more expensive operation.
OK, but what exactly is the benefit here? The cpu time will have to be spent
in any case, but we move it to a context that's not accounted to the exiting
process. Is that good? Also if it's a large process and restarts
immediately, allocating all the memory back again, it might not be available
as it's still being freed in the background, leading to a risk of OOM?
> There is mmdrop_async(), and I wondered if one could reuse that concept when
> tearing down a process -- I didn't look into feasibility, however, so it's
> just some very rough idea.
>
next prev parent reply other threads:[~2021-10-08 12:38 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20211008063933.331989-1-ultrachin@163.com>
2021-10-08 8:17 ` [PATCH] mm: Free per cpu pages async to shorten program exit time David Hildenbrand
2021-10-08 8:52 ` Claudio Imbrenda
2021-10-08 9:15 ` David Hildenbrand
2021-10-08 9:22 ` Claudio Imbrenda
2021-10-08 9:24 ` David Hildenbrand
2021-10-08 12:38 ` Vlastimil Babka [this message]
2021-10-08 12:54 ` Claudio Imbrenda
2021-10-08 12:55 ` David Hildenbrand
2021-10-10 22:42 ` Andrew Morton
2021-10-11 9:28 ` Michal Hocko
2021-10-11 9:40 ` David Hildenbrand
2021-10-11 11:23 ` Michal Hocko
2021-10-13 17:38 ` Daniel Jordan
2021-10-08 11:27 ` kernel test robot
2021-10-08 12:29 ` kernel test robot
2021-10-11 8:20 ` [mm] 3e55b36596: kernel_BUG_at_mm/page_alloc.c kernel test robot
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