On Mon, 16 Apr 2001 12:36:03 +0200,
Poul-Henning Kamp <[EMAIL PROTECTED]> said:
Poul-Henning> In message <[EMAIL PROTECTED]>,
Seigo Tanim
Poul-Henning> ura writes:
>> Those pieces of work were done in the last weekend, and the patch at
>>
Seigo> http://people.FreeBSD.org/~tanimura/patches/vnrecycle.diff
>>
>> has been updated and now ready to commit.
Poul-Henning> I'm a bit worried about the amount of work done in the
Poul-Henning> cache_purgeleafdirs(), considering how often it is called,
Poul-Henning> Do you have measured the performance impact of this to be an
Poul-Henning> insignificant overhead ?
No precise results right now, mainly because I cannot find a benchmark
to measure the performance of name lookup going down to a deep
directory depth.
It has been confirmed, though, that the hit ratio of name lookup is
around 96-98% for a box serving cvsup both with and without my patch
(observed by systat(1)). Here are the details of the name lookup on
that box:
Frequency: Around 25,000-35,000 lookups/sec at most,
8,000-10,000 generally.
Name vs Directory: 98% or more of the lookups are for names, the
rest of them are for directories (up to 1.5%
of the whole lookup at most).
Hit ratio: 96-98% for names and up to 1% at most for
directories (both with and without my patch)
Considering that most of lookup operations are for names and its hit
ratio is not observed to degrade, and assuming that the time consumed
for lookup hit is always constant, the performance of lookup is not
found to be deteriorated.
For a more precise investigation, we have to measure the actial time
taken for a lookup operation, in which case I may have to write a
benchmark for it and test in single-user mode.
It is interesting that the hit ratio of directory lookup is up to only
1% at most, even without my patch. Why is it like that?
--
Seigo Tanimura <[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
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