From: Andrea Arcangeli <andrea@suse.de>
To: Jens Axboe <axboe@suse.de>
Cc: Andrew Morton <akpm@osdl.org>, Chris Mason <mason@suse.com>,
marcelo@conectiva.com.br, linux-kernel@vger.kernel.org,
akpm@digeo.com
Subject: Re: RFC on io-stalls patch
Date: Tue, 15 Jul 2003 11:48:26 +0200 [thread overview]
Message-ID: <20030715094826.GF30537@dualathlon.random> (raw)
In-Reply-To: <20030715082850.GH833@suse.de>
On Tue, Jul 15, 2003 at 10:28:50AM +0200, Jens Axboe wrote:
> no_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.21 3 133 197.0 0.0 0.0 1.00
> 2.4.22-pre5 2 134 196.3 0.0 0.0 1.00
> 2.4.22-pre5-axboe 3 133 196.2 0.0 0.0 1.00
> ctar_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.21 3 190 140.5 15.0 15.8 1.43
> 2.4.22-pre5 3 235 114.0 25.0 22.1 1.75
> 2.4.22-pre5-axboe 3 194 138.1 19.7 20.6 1.46
>
> 2.4.22-pre5-axboe is way better than 2.4.21, look at the loads
> completed.
>
> xtar_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.21 3 287 93.0 14.0 15.3 2.16
> 2.4.22-pre5 3 309 86.4 15.0 14.9 2.31
> 2.4.22-pre5-axboe 3 249 107.2 11.3 14.1 1.87
>
> 2.4.21 beats 2.4.22-pre5, not too surprising and expected, and not
> terribly interesting either.
>
> io_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.21 3 543 49.7 100.4 19.0 4.08
> 2.4.22-pre5 3 637 42.5 120.2 18.5 4.75
> 2.4.22-pre5-axboe 3 540 50.0 103.0 18.1 4.06
>
> 2.4.22-pre5-axboe completes the most loads here per time unit.
>
> io_other:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.21 3 581 46.5 111.3 19.1 4.37
> 2.4.22-pre5 3 576 47.2 107.7 19.8 4.30
> 2.4.22-pre5-axboe 3 452 59.7 85.3 19.5 3.40
>
> 2.4.22-pre5 is again the slowest of the lot when it comes to
> workloads/time, 2.4.22-pre5 is again the fastest and completes the work
> load in the shortest time.
>
> read_load:
> Kernel [runs] Time CPU% Loads LCPU% Ratio
> 2.4.21 3 151 180.1 8.3 9.3 1.14
> 2.4.22-pre5 3 150 181.3 8.1 9.3 1.12
> 2.4.22-pre5-axboe 3 152 178.9 8.2 9.9 1.14
>
> Pretty equal.
io_other and xtar_load aren't exactly equal. As for elevator-lowlatency
alone I'm not sure why it doesn't show big benefits in the above
workloads. It was very noticeable in my tests where I normally counted
the lines per second in `find /` or `time ls` (from comparisons with
contest with previous kernels w/o elevator-lowlatency, it looked like it
made a difference too and I've got some positive feedback). Maybe it's
because we enlarged the queue size to 4M in this version, in the
original patches where I run most of the latency tests it was 2M but I
was concerned that it could be too small.
If it doesn't take too much time, I would be curious what happens if
you change:
MAX_QUEUE_SECTORS (4 << (20 - 9))
to
MAX_QUEUE_SECTORS (2 << (20 - 9))
(it's up to you if to apply your patch or not along with this change, it
should make a noticeable difference either ways)
Obviously, the smaller the queue, the higher the fairness and the lower
the latency, but the smaller the pipelining will be in the I/O queue, so
it'll be less guaranteed to keep the spindle constantly working, not an
issue for all low end devices though. Ideally it should be tunable per-device.
on a 50mbyte/sec array 2M didn't show any degradation either during
contigous I/O, but I didn't run any test on faster storages, so I felt
safer to use 4M in the latest versions, knowing latency would be
slightly hurted.
Andrea
next prev parent reply other threads:[~2003-07-15 9:33 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 [this message]
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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