From: Jens Axboe <axboe@suse.de>
To: kumon@flab.fujitsu.co.jp
Cc: linux-kernel@vger.kernel.org, Dave Jones <davej@suse.de>,
Andrea Arcangeli <andrea@suse.de>
Subject: Re: [PATCH] livelock in elevator scheduling
Date: Tue, 21 Nov 2000 12:36:08 +0100 [thread overview]
Message-ID: <20001121123608.F10007@suse.de> (raw)
In-Reply-To: <200011210838.RAA27382@asami.proc.flab.fujitsu.co.jp> <20001121112836.B10007@suse.de> <200011211130.UAA27961@asami.proc.flab.fujitsu.co.jp>
In-Reply-To: <200011211130.UAA27961@asami.proc.flab.fujitsu.co.jp>; from kumon@flab.fujitsu.co.jp on Tue, Nov 21, 2000 at 08:30:33PM +0900
On Tue, Nov 21 2000, kumon@flab.fujitsu.co.jp wrote:
> > Believe it or not, but this is intentional. In that regard, the
> > function name is a misnomer -- call it i/o scheduler instead :-)
>
> I never believe it intentional. If it is true, the current kernel
> will be suffered from a kind of DOS attack. Yes, actually I'm a
> victim of it.
The problem is caused by the too high sequence numbers in stock
kernel, as I said. Plus, the sequence decrementing doesn't take
request/buffer size into account. So the starvation _is_ limited,
the limit is just too high.
> By Running ZD's ServerBench, not only the performance down, but my
> machine blocks all commands execution including /bin/ps, /bin/ls... ,
> and those are not ^C able unless the benchmark is stopped. Those
> commands are read from disks but the requests are wating at the end of
> I/O queue, those won't be executed.
If performance is down, then that problem is most likely elsewhere.
I/O limited benchmarking typically thrives on lots of request
latency -- with that comes better throughput for individual threads.
> Anyway, I'll try your patch.
Thanks
--
* Jens Axboe <axboe@suse.de>
* SuSE Labs
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next prev parent reply other threads:[~2000-11-21 12:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-11-21 8:38 [PATCH] livelock in elevator scheduling kumon
2000-11-21 10:28 ` Jens Axboe
2000-11-21 11:30 ` kumon
2000-11-21 11:36 ` Jens Axboe [this message]
2000-12-02 0:22 ` Russell Cattelan
2000-12-02 15:42 ` Jens Axboe
2000-12-04 23:25 ` Russell Cattelan
2000-12-05 1:38 ` Russell Cattelan
2000-12-05 23:01 ` Jens Axboe
2000-12-06 0:53 ` Russell Cattelan
2000-11-21 12:39 ` kumon
2000-11-21 13:01 ` Jens Axboe
2000-11-22 6:08 ` kumon
2000-11-22 10:59 ` kumon
2000-11-22 15:50 ` davej
[not found] <200011210828.RAA27311@asami.proc.flab.fujitsu.co.jp>
2000-11-21 15:12 ` Andrea Arcangeli
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