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From: kumon@flab.fujitsu.co.jp
Date: Wed, 22 Nov 2000 19:59:38 +0900
Message-Id: <200011221059.TAA03907@asami.proc.flab.fujitsu.co.jp>
To: Jens Axboe <axboe@suse.de>
Cc: kumon@flab.fujitsu.co.jp, linux-kernel@vger.kernel.org,
        Dave Jones <davej@suse.de>, Andrea Arcangeli <andrea@suse.de>
Subject: Re: [PATCH] livelock in elevator scheduling
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Jens Axboe writes:
 > I'd be very interested if you could repeat your test with my
 > block patch applied. It has, among other things, a more fair (and
 > faster) insertion.
 > 
 > *.kernel.org/pub/linux/kernel/people/axboe/patches/2.4.0-test11/blk-11.bz2

This patch fixes the "DoS" behavior of the current queuing mechanism.
Even if I set the "pass-over" values to very large number (1000000) it
stably runs.
Thank you for your patch.

>From my understanding, passover is an option of the elevator
scheduling to prioritize long waiting requests for improving online
responses.  In that test, passover value setting doesn't affect the
benchmark number, which is probable.

Will the patch is included in the next kernel?


BTW,
The major performance difference between test1 and test2 was caused by
whether the hard_dirty_limit is hit or not.

The current Linux has a lot of difficult to set parameters in
/proc/sys.
 Once a system goes beyond some settable limits, the system behavior
changes so sharp.  Bdf_prm.nrfract in fs/buffer.c is one of the
difficult parameters.  I hope a tool to monitor or set these value.

--
Computer Systems Laboratory, Fujitsu Labs.
kumon@flab.fujitsu.co.jp
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