Re: [RFC] changes to buffer.c (was Test12 ll_rw_block error)

From: Chris Mason (
Date: Wed Dec 27 2000 - 15:49:20 EST

On Wednesday, December 27, 2000 21:26:02 +0100 Daniel Phillips
<> wrote:

> Hi Chris. I took your patch for a test drive under dbench and it seems
> impressively stable under load, but there are performance problems.
> Test machine: 64 meg, 500 Mhz K6, IDE, Ext2, Blocksize=4K
> Without patch: 9.5 MB/sec, 11 min 6 secs
> With patch: 3.12 MB/sec, 33 min 51 sec

Cool, thanks for the testing. Which benchmark are you using? bonnie and
dbench don't show any changes on my scsi disks, I'll give IDE a try as well.

> Philosophically, I wonder if it's right for the buffer flush mechanism
> to be calling into the filesystem. It seems like the buffer lists
> should stay sitting between the filesystem and the block layer, it
> actually does a pretty good job.
What I'm looking for is a separation of the write management (aging, memory
pressure, etc, etc) from the actual write method. The lists (VM, buffer.c,
whatever) should do the management, and the FS should do the i/o. This
patch is not a perfect solution by any means, but its a start.


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