[Pdx-pm] string comparison vs hash
chromatic at wgz.org
Tue May 29 23:58:08 PDT 2007
On Tuesday 29 May 2007 23:47:38 Eric Wilhelm wrote:
> # on Tuesday 29 May 2007 03:54 pm:
> >Worse than that, the first code to read the file pays the penalty of
> >populating file buffers. Subsequent reads probably all come from a
> > warm cache.
> Are we talking operating-system cache or perl guts?
> And, if only the OS, is there anything tying that to a given process?
Not in any OS I know. (NB: I understand how a modern Unix works, which means
nothing when it comes to Windows or anything as exotic as Mac OS X.)
> I'm under the impression that given a linux machine which is not
> actively swapping memory that the cache is as warm as it is going to
> get after e.g. 'grep . file > /dev/null'. Other than obvious machine
> load, is there anything else going on there WRT per-process caching or
Perl, no. OS--depends.
Still, if the benchmark's fast enough to say "I didn't run enough iterations
to get a reliable count", I start to suspect that seek time and transfer
rates will suddenly start to matter a lot more than the difference between
indexed and keyed aggregate access.
Accurate benchmarking is Not Easy.
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