Messages in this thread | | | Date | Mon, 14 Apr 2003 22:35:37 -0700 | From | Andrew Morton <> | Subject | Re: 2.5.67-mm3 |
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William Lee Irwin III <wli@holomorphy.com> wrote: > > On Mon, Apr 14, 2003 at 09:55:41PM -0700, Andrew Morton wrote: > > Sort-of. The code is doing two things. > > a) Make sure that all the relevant pte's are established in the correct > > state so we don't take a fault while holding the subsequent atomic kmap. > > This is just an optimisation. If we _do_ take the fault while holding > > an atomic kmap, we fall back to sleeping kmap, and do the whole copy > > again. It almost never happens. > > This is the easy part; we're basically just prefaulting.
btw, this may sound like a lot of futzing about, but the other day I timed four concurrent instances of
dd if=/dev/zero of=$i bs=1 count=1M
on the four-way. 2.5 ran eight times faster than 2.4. 2.4's kmap_lock contention was astonishing.
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