On 9/9/05, Roger Heflin <rheflin@xxxxxxxxx> wrote:
I saw it mentioned before that the kernel only allows a certain
percentage of total memory to be dirty, I thought the number was
around 40%, and I have seen machines with large amounts of ram,
hit the 40% and then put the writing application into disk wait
until certain amounts of things are written out, and then take
it out of disk wait, and repeat when it again hits 40%, given your
rate different it would be close to 40% in 50seconds.
yes, on 2.6 there are two tunables which are important here. dirty_background_ratio is the threshold where the kernel will begin
flushing dirty buffers, so it should change how soon the disk becomes
active. dirty_ratio changes when the write-throttling code kicks in,
which is what Anthony is seeing. The purpose of the write throttling
code is to limit the dirtying process to disk bandwidth, so that is a
Feature. Anthony, try *increasing* dirty_ratio, you can go up to 100,
but you could trigger an OOM if you let it get too high, so maybe try
setting it at 85 or so. This should effectively disable the write
throttling and give you the bandwidth you want.
NATE
And I think that you mean MB(yte) not Mb(it).
Roger
-----Original Message-----
From: linux-kernel-owner@xxxxxxxxxxxxxxx [mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of Anthony Wesley
Sent: Friday, September 09, 2005 4:11 AM
To: linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: kernel 2.6.13 buffer strangeness
Thanks David, but if you read my original post in full you'll see that I've tried that, and while I can start the write out sooner by lowering /proc/sys/vm/dirty_ratio , it makes no difference to the results that I am getting. I still seem to run out of steam after only 50 seconds where it should take about 3 minutes.
regards, Anthony
--
Anthony Wesley
Director and IT/Network Consultant
Smart Networks Pty Ltd
Acquerra Pty Ltd
Anthony.Wesley@xxxxxxxxxxxxxxx
Phone: (02) 62595404 or 0419409836
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