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

On Sun, 5 Aug 2007 22:21:12 +0200 Jorn Engel [off-list ref] wrote:

On Sun, 5 August 2007 20:37:14 +0200, Jorn Engel wrote:

quoted

Guess I should throw in a kernel compile test as well, just to get a
feel for the performance.

Three runs each of noatime, relatime and atime, both with cold caches
and with warm caches.  Scripts below.  Run on a Thinkpad T40, 1.5GHz,
2GiB RAM, 60GB 2.5" IDE disk, ext3.

Biggest difference between atime and noatime (median run, cold cache) is
~2.3%, nowhere near the numbers claimed by Ingo.  Ingo, how did you
measure 10% and more?

Ingo had CONFIG_DEBUG_INFO=y, which generates heaps more writeout,
but no additional atime updates.

Ingo had a faster computer ;)  That will generate many more MB/sec
write traffic, so the cost of those atime seeks becomes proportionally
higher.  Basically: you're CPU-limited, Ingo is seek-limited.

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