Ingo Molnar wrote:
* Alan Cox <[email protected]> wrote:
People just need to know about the performance differences - very
few realise its more than a fraction of a percent. I'm sure Gentoo
will use relatime the moment anyone knows its > 5% 8)
noatime,nodiratime gave 50% of wall-clock kernel rpm build
performance improvement for Dave Jones, on a beefy box. Unless i
misunderstood what you meant under 'fraction of a percent' your
numbers are _WAY_ off.
What numbers - I didn't quote any performance numbers ?
ok, i misunderstood your "very few realise its more than a fraction of a
percent" sentence, i thought you were saying it's a fraction of a
percent.
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.
Greg
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