All of lore.kernel.org
 help / color / mirror / Atom feed
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.

WARNING: multiple messages have this Message-ID (diff)
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.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  reply	other threads:[~2016-09-27  8:13 UTC|newest]

Thread overview: 38+ 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 16:43 ` Vlastimil Babka
2016-09-22 16:49 ` Eric Dumazet
2016-09-22 16:49   ` Eric Dumazet
2016-09-22 16:49   ` Eric Dumazet
2016-09-22 16:56   ` Vlastimil Babka
2016-09-22 16:56     ` Vlastimil Babka
2016-09-22 17:07     ` Eric Dumazet
2016-09-22 17:07       ` Eric Dumazet
2016-09-22 17:07       ` Eric Dumazet
2016-09-22 17:55       ` Vlastimil Babka
2016-09-22 17:55         ` Vlastimil Babka
2016-09-23  9:42         ` David Laight
2016-09-23  9:58           ` Vlastimil Babka
2016-09-23  9:58             ` Vlastimil Babka
2016-09-23  9:58             ` Vlastimil Babka
2016-09-23 13:35             ` David Laight
2016-09-26 10:01               ` Vlastimil Babka
2016-09-26 10:01                 ` Vlastimil Babka
2016-09-26 15:02                 ` David Laight
2016-09-25 18:50   ` Andi Kleen
2016-09-25 18:50     ` Andi Kleen
2016-09-27  0:01 ` Andrew Morton
2016-09-27  0:01   ` Andrew Morton
2016-09-27  1:38   ` Eric Dumazet
2016-09-27  1:38     ` Eric Dumazet
2016-09-27  1:38     ` Eric Dumazet
2016-09-27  8:13     ` Vlastimil Babka [this message]
2016-09-27  8:13       ` Vlastimil Babka
2016-09-27 13:34       ` Eric Dumazet
2016-09-27 13:34         ` Eric Dumazet
2016-09-27 13:34         ` Eric Dumazet
2016-09-27  8:06   ` Vlastimil Babka
2016-09-27  8:06     ` Vlastimil Babka
2016-09-27  8:45 ` [PATCH v3] " Vlastimil Babka
2016-09-27  8:45   ` Vlastimil Babka
2016-09-27 10:22   ` Michal Hocko
2016-09-27 10:22     ` Michal Hocko

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=6e62a278-4ac3-a866-51c6-e32511406aba@suse.cz \
    --to=vbabka@suse.cz \
    --cc=akpm@linux-foundation.org \
    --cc=eric.dumazet@gmail.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.