Re: [devel] [PATCH 0/3] optimize rpmsetcmp()

["Dmitry V. Levin" <ldv@altlinux.org>]

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On Sun, Dec 05, 2010 at 02:41:31AM +0300, Alexey Tourbin wrote:
> On Sun, Dec 05, 2010 at 02:26:44AM +0300, Dmitry V. Levin wrote:
> > On Sun, Dec 05, 2010 at 12:28:31AM +0300, Alexey Tourbin wrote:
> > [...]
> > > What you urge to do is to cut down the price even more.  But there is
> > > clearly something wrong with apt, as it tries to resolve every single
> > > dependency upon every startup.  And, fortunately, it takes only a few
> > > seconds!
> > 
> > It will take twice or trice longer time when _all_ packages with ELF
> > files will get their set-versioned dependencies, so I expect apt-get
> > startup will eventually be about 10x slower again (compared to 5.1 branch).
> > 
> > apt-rpm indeed calls rpmRangesOverlap() too many times, it's common
> > knowledge.  Unfortunately, stating this fact isn't sufficient to make
> > apt-rpm work faster.
> 
> So what do you think?  There's a possibility to change bitv[] to bitmap,
> per Kirill's proposal.  That mighit yield about, say 30% user time cutdown.

30% is a bit optimistic, according to my measurements.

> However, note that apt is not only eager for user time.  System time is
> being spent with splendor as well.

System time takes only about 15% of elapsed time, according to my
measurements.

> Personally, I like bitv[], and I don't like something like <sys/select.h> stuff.

When performance is the issue, there should be a good rationale to choose
the approach that works slower.


-- 
ldv

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