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Re: Faster compilation speed: cache behavior
- From: Mike Stump <mrs at apple dot com>
- To: Geoff Keating <geoffk at geoffk dot org>
- Cc: Matt Austern <austern at apple dot com>, gcc at gcc dot gnu dot org
- Date: Tue, 20 Aug 2002 16:01:47 -0700
- Subject: Re: Faster compilation speed: cache behavior
On Tuesday, August 20, 2002, at 03:45 PM, Geoff Keating wrote:
Does Apple's memset use dcbz? I'm curious why memset should cause any
cache misses at all.
The symbols mentioned are just one possible value of the pc within the
millisecond (by default) when the sample was taken. The sample
collects all the events of interest. Because memset consumes massive
amounts of time, it naturally stops off in this routine, and it is
tagged as `responsible' for the stats, even though, it need not have
much to do with it. I'd guess though, much of the time the correlation
is interesting however.
So, for example:
void foo() {
routine that takes time
memset
another routine
}
the events from one or the other routine (I'd have to re-read the doc,
or try an experiment to be sure) can show up in a line called memset.