From: Chris Mason <mason@suse.com>
To: Andrea Arcangeli <andrea@suse.de>
Cc: Marcelo Tosatti <marcelo@conectiva.com.br>,
Jens Axboe <axboe@suse.de>, lkml <linux-kernel@vger.kernel.org>,
"Stephen C. Tweedie" <sct@redhat.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Jeff Garzik <jgarzik@pobox.com>, Andrew Morton <akpm@digeo.com>,
Alexander Viro <viro@math.psu.edu>
Subject: Re: RFC on io-stalls patch
Date: 14 Jul 2003 16:34:41 -0400 [thread overview]
Message-ID: <1058214881.13313.291.camel@tiny.suse.com> (raw)
In-Reply-To: <20030714202434.GS16313@dualathlon.random>
On Mon, 2003-07-14 at 16:24, Andrea Arcangeli wrote:
>
> this isn't what we had in pre4, this is more equivalent to an hack in
> pre4 where the requests aren't distributed anymore 50/50 but 10/90. Of
> course an I/O queue filled mostly by parallel sync reads, will make the
> writer go slower since it will very rarely find the queue not oversized
> in presence of a flood of readers. So the writer won't be able to make
> progress.
>
> This is a "stop the writers and give unlimited requests to the reader"
> hack, not a "reserve some request for the reader", of course then the
> reader is faster. of course then, contest shows huge improvements for
> the read loads.
Which is why it's a good place to start. If we didn't see huge
improvements here, there's no use in experimenting with this tactic
further.
>
> But contest only benchmarks the reader, it has no clue how fast the
> writer is AFIK. I would love to hear the bandwidth the writer is writing
> into the xtar_load. Maybe it's shown in some of the Loads/LCPU or
> something, but I don't know the semantics of those fields and I only
> look at time and ratio which I understand. so if any contest expert can
> enaborate if the xtar_load bandwidth is taken into consideration
> somewhere I would love to hear.
I had a much longer reply at first as well, but this is only day 1 of
Jens' benchmark, and he had plans to test other workloads. I'd like to
give him the chance to do that work before we think about merging the
patch. It's a good starting point for the question "can we do better
for reads?" (clearly the answer is yes).
-chris
next prev parent reply other threads:[~2003-07-14 20:25 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 [this message]
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
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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