Re: [PATCH 00/23] per device dirty throttling -v8

From: david
Date: Wed Aug 08 2007 - 21:31:10 EST


On Thu, 9 Aug 2007, Greg Trounson wrote:

Measurements show that noatime helps 20-30% on regular desktop workloads,
easily 50% for kernel builds and much more than that (in excess of 100%)
for file-read-intense workloads. We cannot just walk past such a _huge_
performance impact so easily without even reacting to the performance
arguments, and i'm happy Ubuntu picked up noatime,nodiratime and is
whipping up the floor with Fedora on the desktop.


Sorry I'm just not seeing those gains here. With my filesystems mounted with atime defaults the Quake sources build in 1m28.856s. A test with ls -ltu verifies that atime is working as expected. When I remount my filesystems with:
mount [fs] -o remount,noatime,nodiratime
I get a compile time of 1m23.368s, a mere 6% improvement.

This is on a dual-core Athlon 4200+ box running 2.6.21, so I would have thought this to be close to a best-case file I/O test.

what sort of disks does this box have? and what filesystem? slower disks/filesystems can result in this showing a larger difference.

however 6% is a fairly significant gain.

David Lang
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