Messages in this thread | | | From | Leroy van Logchem <> | Subject | Re: [RFC][PATCH 0/3] VM throttling: avoid blocking occasional writers | Date | Fri, 2 Mar 2007 13:06:30 +0000 (UTC) |
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> I'm sorry to piggy-back this thread. > > Could it be what I'm experiencing in the following bugzilla report: > http://bugzilla.kernel.org/show_bug.cgi?id=7372 > > As I explained in the report, I see this issue only since 2.6.18. > So if your concern is related to mine, what could have changed between > 2.6.17 and 2.6.18 related to this?
I don't think it's 2.6.x related, it's been under the sheets from start.
Related to your problem in the 7372 bug:
Pages are kept in memory for re-use, which is fast and fine except for: 1) data without re-use value or even single use 2) applications _do not_ advise the kernel how to cache pages related to there self generated i/o. POSIX does provide mechanisms to properly do so. But the kernel should help these poor apps.
To minimize your MySQL backup cp(1) problem, try this workaround:
cat ./cp_direct.sh #!/bin/sh dd if=$1 of=$2 bs=1M iflag=direct oflag=direct
Combine this with [/etc/sysctl.conf]:
vm.vfs_cache_pressure = 1 vm.dirty_ratio = 2 vm.dirty_background_ratio = 1
This should reduce both the stress on the vm and response latency during interactive work.
-- Leroy
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