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From: Andrew Morton <akpm@zip.com.au>
To: Andrea Arcangeli <andrea@suse.de>
Cc: Stephan von Krawczynski <skraw@ithnet.com>,
	jogi@planetzork.ping.de, linux-kernel@vger.kernel.org
Subject: Re: 2.4.10-pre11: alsaplayer skiping during kernel build (-pre10 did  not)
Date: Tue, 18 Sep 2001 13:02:27 -0700	[thread overview]
Message-ID: <3BA7A853.4EC44195@zip.com.au> (raw)
In-Reply-To: <20010918171416.A6540@planetzork.spacenet> <20010918172500.F19092@athlon.random> <20010918173515.B6698@planetzork.spacenet> <20010918174434.I19092@athlon.random> <20010918175104.D6698@planetzork.spacenet> <20010918212856.50cd5b87.skraw@ithnet.com>, <20010918212856.50cd5b87.skraw@ithnet.com>; from skraw@ithnet.com on Tue, Sep 18, 2001 at 09:28:56PM +0200 <20010918214152.A720@athlon.random>

Andrea Arcangeli wrote:
> 
> I now have an update ready for Linus to merge that should fix the few
> leftovers I had in the very first release of the vm rewrite but of
> course I will be interested to hear about any regression/progression
> about those changes, I'll post them in a few minutes in CC to l-k.
> 

Please include Andi's likely()/unlikely() change - it's nice.

I can't measure any obviously new causes of latency in your
VM.  It's nice that you've paid attention to this in various
places.

The main culprits now are the file IO and dirty buffer writeout paths:
up to fifty milliseconds in each.

I suggest you stick scheduling points in generic_file_read(),
generic_file_write() and write_locked_buffers() and then dispose
of the copy-user-latency patch from -aa kernels.

With the above fixed, the main source of latency is
/proc/meminfo->si_swapinfo(). It's about five milliseconds per gig
of swap, which isn't too bad.  But it's directly invokable by
userspace (ie: /usr/bin/top) and really should be made less dumb.

  reply	other threads:[~2001-09-18 20:02 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-09-18 15:14 jogi
2001-09-18 15:25 ` Andrea Arcangeli
2001-09-18 15:35   ` jogi
2001-09-18 15:44     ` Andrea Arcangeli
2001-09-18 15:51       ` jogi
2001-09-18 16:06       ` jogi
2001-09-18 19:28       ` Stephan von Krawczynski
2001-09-18 19:41         ` Andrea Arcangeli
2001-09-18 20:02           ` Andrew Morton [this message]
2001-09-18 20:18             ` Andrea Arcangeli
2001-09-19 12:37             ` Hugh Dickins
2001-09-19 13:21       ` jogi
2001-09-19 14:38       ` jogi
2001-09-18 15:25 ` jogi
2001-09-18 15:31   ` Andrea Arcangeli
2001-09-18 15:43     ` jogi

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