From: Vlastimil Babka <vbabka@suse.cz>
To: Eric Dumazet <eric.dumazet@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, Michal Hocko <mhocko@kernel.org>,
netdev@vger.kernel.org
Subject: Re: [PATCH v2] fs/select: add vmalloc fallback for select(2)
Date: Tue, 27 Sep 2016 10:13:16 +0200 [thread overview]
Message-ID: <6e62a278-4ac3-a866-51c6-e32511406aba@suse.cz> (raw)
In-Reply-To: <1474940324.28155.44.camel@edumazet-glaptop3.roam.corp.google.com>
On 09/27/2016 03:38 AM, Eric Dumazet wrote:
> On Mon, 2016-09-26 at 17:01 -0700, Andrew Morton wrote:
>
>> I don't share Eric's concerns about performance here. If the vmalloc()
>> is called, we're about to write to that quite large amount of memory
>> which we just allocated, and the vmalloc() overhead will be relatively
>> low.
>
> I did not care of the performance of this particular select() system
> call really, but other cpus because of more TLB invalidations.
There are many other ways to cause those, AFAIK. The reclaim/compaction
for order-3 allocation has its own impact on system, including TLB flushes.
Or a flood of mmap(MAP_POPULATE) and madvise(MADV_DONTNEED) calls...
This vmalloc() would however require raising RLIMIT_NOFILE above the defaults.
> At least CONFIG_DEBUG_PAGEALLOC=y builds should be impacted, but maybe
> we do not care.
I doubt anyone runs that in production, especially if performance is of concern.
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next prev parent reply other threads:[~2016-09-27 8:13 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-22 16:43 [PATCH v2] fs/select: add vmalloc fallback for select(2) Vlastimil Babka
2016-09-22 16:49 ` Eric Dumazet
2016-09-22 16:56 ` Vlastimil Babka
2016-09-22 17:07 ` Eric Dumazet
2016-09-22 17:55 ` Vlastimil Babka
2016-09-23 9:42 ` David Laight
2016-09-23 9:58 ` Vlastimil Babka
2016-09-23 13:35 ` David Laight
2016-09-26 10:01 ` Vlastimil Babka
2016-09-26 15:02 ` David Laight
2016-09-25 18:50 ` Andi Kleen
2016-09-27 0:01 ` Andrew Morton
2016-09-27 1:38 ` Eric Dumazet
2016-09-27 8:13 ` Vlastimil Babka [this message]
2016-09-27 13:34 ` Eric Dumazet
2016-09-27 8:06 ` Vlastimil Babka
2016-09-27 8:45 ` [PATCH v3] " Vlastimil Babka
2016-09-27 10:22 ` Michal Hocko
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