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From: Andrea Arcangeli <andrea@suse.de>
To: Jens Axboe <axboe@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
	Marcelo Tosatti <marcelo@conectiva.com.br>,
	Chris Mason <mason@suse.com>, lkml <linux-kernel@vger.kernel.org>,
	"Stephen C. Tweedie" <sct@redhat.com>,
	Jeff Garzik <jgarzik@pobox.com>, Andrew Morton <akpm@digeo.com>,
	Alexander Viro <viro@math.psu.edu>
Subject: Re: RFC on io-stalls patch
Date: Wed, 16 Jul 2003 14:43:55 +0200	[thread overview]
Message-ID: <20030716124355.GE4978@dualathlon.random> (raw)
In-Reply-To: <20030715112737.GQ833@suse.de>

On Tue, Jul 15, 2003 at 01:27:37PM +0200, Jens Axboe wrote:
> On Tue, Jul 15 2003, Alan Cox wrote:
> > On Maw, 2003-07-15 at 06:26, Jens Axboe wrote:
> > > Sorry, but I think that is nonsense. This is the way we have always
> > > worked. You just have to maintain a decent queue length still (like we
> > > always have in 2.4) and there are no problems.
> > 
> > The memory pinning problem is still real - and always has been. It shows up
> > best not on IDE disks but large slow media like magneto opticals where you
> > can queue lots of I/O but you get 500K/second
> 
> Not the same thing. On slow media, like dvd-ram, what causes the problem
> is that you can dirty basically all of the RAM in the system. That has
> nothing to do with memory pinned in the request queue.

you can trivially bound the amount of dirty memory to nearly 0% with the
bdflush sysctl. And the overkill size of the queue until pre3 could be
an huge VM overhead compared to the dirty memory on lowmem boxes,
example a 32/64M machine. So I disagree it's only a mistake of write
throttling that gives problems on slow media.

Infact I tend to think the biggest problem for slow media in 2.4 is the
lack of per spindle pdflush.

Andrea

  reply	other threads:[~2003-07-16 12:29 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-07-08 20:06 RFC on io-stalls patch Marcelo Tosatti
2003-07-10 13:57 ` Jens Axboe
2003-07-11 14:13   ` Chris Mason
2003-07-12  0:20     ` Nick Piggin
2003-07-12 18:37       ` Chris Mason
2003-07-12  7:37     ` Jens Axboe
2003-07-12  7:48       ` Jens Axboe
2003-07-12 18:32       ` Chris Mason
2003-07-13  0:33         ` Andrea Arcangeli
2003-07-13  9:01         ` Jens Axboe
2003-07-13 16:20           ` Chris Mason
2003-07-13 16:45             ` Jeff Garzik
2003-07-13 19:33               ` Andrea Arcangeli
2003-07-13 17:47             ` Jens Axboe
2003-07-13 19:35               ` Andrea Arcangeli
2003-07-14  0:36                 ` Chris Mason
2003-07-13 19:19           ` Andrea Arcangeli
2003-07-14  5:49             ` Jens Axboe
2003-07-14 12:23               ` Marcelo Tosatti
2003-07-14 13:12                 ` Jens Axboe
2003-07-14 19:51                   ` Jens Axboe
2003-07-14 20:09                     ` Chris Mason
2003-07-14 20:19                       ` Andrea Arcangeli
2003-07-14 21:24                         ` Chris Mason
2003-07-15  5:46                       ` Jens Axboe
2003-07-14 20:09                     ` Marcelo Tosatti
2003-07-14 20:24                       ` Andrea Arcangeli
2003-07-14 20:34                         ` Chris Mason
2003-07-15  5:35                           ` Jens Axboe
     [not found]                           ` <20030714224528.GU16313@dualathlon.random>
2003-07-15  5:40                             ` Jens Axboe
     [not found]                             ` <1058229360.13317.364.camel@tiny.suse.com>
2003-07-15  5:43                               ` Jens Axboe
     [not found]                               ` <20030714175238.3eaddd9a.akpm@osdl.org>
     [not found]                                 ` <20030715020706.GC16313@dualathlon.random>
2003-07-15  5:45                                   ` Jens Axboe
2003-07-15  6:01                                     ` Andrea Arcangeli
2003-07-15  6:08                                       ` Jens Axboe
2003-07-15  7:03                                         ` Andrea Arcangeli
2003-07-15  8:28                                           ` Jens Axboe
2003-07-15  9:12                                             ` Chris Mason
2003-07-15  9:17                                               ` Jens Axboe
2003-07-15  9:18                                                 ` Jens Axboe
2003-07-15  9:30                                                   ` Chris Mason
2003-07-15 10:03                                                   ` Andrea Arcangeli
2003-07-15 10:11                                                     ` Jens Axboe
2003-07-15 14:18                                                 ` Chris Mason
2003-07-15 14:29                                                   ` Jens Axboe
2003-07-16 17:06                                                   ` Chris Mason
2003-07-15  9:22                                               ` Chris Mason
2003-07-15  9:59                                               ` Andrea Arcangeli
2003-07-15  9:48                                             ` Andrea Arcangeli
2003-07-14 20:16                     ` Andrea Arcangeli
2003-07-14 20:17                       ` Marcelo Tosatti
2003-07-14 20:27                         ` Andrea Arcangeli
2003-07-15  5:26                       ` Jens Axboe
2003-07-15  5:48                         ` Andrea Arcangeli
2003-07-15  6:01                           ` Jens Axboe
2003-07-15  6:33                             ` Andrea Arcangeli
2003-07-15 11:22                         ` Alan Cox
2003-07-15 11:27                           ` Jens Axboe
2003-07-16 12:43                             ` Andrea Arcangeli [this message]
2003-07-16 12:46                               ` Jens Axboe
2003-07-16 12:59                                 ` Andrea Arcangeli
2003-07-16 13:04                                   ` Jens Axboe
2003-07-16 13:11                                     ` Andrea Arcangeli
2003-07-16 13:21                                       ` Jens Axboe
2003-07-16 13:44                                         ` Andrea Arcangeli
2003-07-16 14:00                                           ` Jens Axboe
2003-07-16 14:24                                             ` Andrea Arcangeli
2003-07-16 16:49                                     ` Andrew Morton
2003-07-15 18:47 Shane Shrybman

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