I remember measuring stuff at the time, but have long lost
the results of it. My likely-biased memory says that kernel
builds went a good 20% faster, and responsiveness under heavy
swapping/paging went up "quite noticeably" -- a term that usually
means at least a factor of two for us humans to notice it.
Somebody else asked about swapping as well, and I now remember that
it was *because* of swapping that I tried this stuff.
It was frustrating to watch my fast drives spend all of their time
seeking back and forth, a page at a time, between the fs and the
swap partition. Implementing "minimal head movement" cured that
symptom, allowing multiple reads/writes to swap to happen together,
dramatically speeding up response under negative-memory conditions.
But as I posted earlier, much has changed (in hardware and in kernel)
in the past 4-5 years, and perhaps different results might be seen
Heck, for that matter, my drives now run with write-caching enabled,
and that alone makes a noticeable difference under load.
The next biggest thing I *currently* do for interactive response
is use a two-drive RAID0 for my (all-in-one) root filesystem.
With a 64KB chunksize, this effectively scatters I/O across both
drives rather evenly (except for metadata, which always seems to
end up on the first drive for some reason..), allowing good response
even while doing full-filesystem-copies and such.
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