From: Rik van Riel <riel@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Phillips <phillips@phunq.net>,
linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC] [PATCH] A clean approach to writeout throttling
Date: Thu, 6 Dec 2007 10:52:42 -0500 [thread overview]
Message-ID: <20071206105242.3e289a21@cuia.boston.redhat.com> (raw)
In-Reply-To: <20071206035511.83bef995.akpm@linux-foundation.org>
On Thu, 6 Dec 2007 03:55:11 -0800
Andrew Morton <akpm@linux-foundation.org> wrote:
> - We a-priori decide to limit a particular stack's peak memory usage to
> 1MB
>
> - We empirically discover that the maximum amount of memory which is
> allocated by that stack on behalf of a single BIO is 16kb. (ie: that's
> the most it has ever used for a single BIO).
>
> - Now, we refuse to feed any more BIOs into the stack when its
> instantaneous memory usage exceeds (1MB - 16kb).
>
> Of course, the _average_ memory-per-BIO is much less than 16kb. So there
> are a lot of BIOs in flight - probably hundreds, but a minimum of 63.
There is only one problem I can see with this. With network block
IO, some memory will be consumed upon IO completion. We need to
make sure we reserve (number of in flight BIOs * maximum amount of
memory consumed upon IO completion) memory, in addition to the
memory you're accounting in your example above.
--
All Rights Reversed
next prev parent reply other threads:[~2007-12-06 15:53 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-06 0:03 [RFC] [PATCH] A clean approach to writeout throttling Daniel Phillips
2007-12-06 1:24 ` Andrew Morton
2007-12-06 6:21 ` Daniel Phillips
2007-12-06 7:31 ` Andrew Morton
2007-12-06 9:48 ` Daniel Phillips
2007-12-06 11:55 ` Andrew Morton
2007-12-06 15:52 ` Rik van Riel [this message]
2007-12-06 17:34 ` Andrew Morton
2007-12-06 17:48 ` Rik van Riel
2007-12-06 20:04 ` Daniel Phillips
2007-12-06 20:27 ` Andrew Morton
2007-12-06 21:27 ` Daniel Phillips
2007-12-06 21:53 ` Bill Davidsen
2007-12-07 0:04 ` Daniel Phillips
2007-12-07 0:29 ` Andrew Morton
2007-12-07 7:13 ` Daniel Phillips
2007-12-10 9:20 ` Daniel Phillips
2007-12-10 10:47 ` Jens Axboe
2007-12-10 11:23 ` [RFC] [PATCH] A clean aEvgeniy pproach " Daniel Phillips
2007-12-10 11:41 ` Jens Axboe
2007-12-10 12:13 ` Daniel Phillips
2007-12-10 12:16 ` Jens Axboe
2007-12-10 12:27 ` Daniel Phillips
2007-12-10 12:32 ` Jens Axboe
2007-12-10 13:04 ` Daniel Phillips
2007-12-10 13:19 ` Jens Axboe
2007-12-10 13:26 ` Daniel Phillips
2007-12-10 13:30 ` Jens Axboe
2007-12-10 13:43 ` Daniel Phillips
2007-12-10 13:53 ` Jens Axboe
2007-12-10 14:17 ` Daniel Phillips
2007-12-11 13:15 ` Jens Axboe
2007-12-11 19:38 ` Daniel Phillips
2007-12-11 20:01 ` Jens Axboe
2007-12-11 20:11 ` Daniel Phillips
2007-12-11 20:07 ` Daniel Phillips
2007-12-10 11:33 ` [RFC] [PATCH] A clean approach " Daniel Phillips
2007-12-10 21:31 ` Jonathan Corbet
2007-12-10 22:06 ` Pekka Enberg
2007-12-11 4:21 ` Daniel Phillips
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