Re: git performance

From: Andreas Ericsson <ae@op5.se>
Date: Oct 23, 2008, 07:43 UTC
Message-ID: <49002B27.50201@op5.se>
In-Reply-To: <m3d4hsi708.fsf@localhost.localdomain>

Jakub Narebski wrote:

Show 25 quoted lines

> "Edward Ned Harvey" <git@nedharvey.com> writes:
> 
>> I see things all over the Internet saying git is fast.  I'm
>> currently struggling with poor svn performance and poor attitude of
>> svn developers, so I'd like to consider switching to git.  A quick
>> question first.
>>
>> The core of the performance problem I'm facing is the need to "walk
>> the tree" for many thousand files.  Every time I do "svn update" or
>> "svn status" the svn client must stat every file to check for local
>> modifications (a coffee cup or a beer worth of stats).  In essence,
>> this is unavoidable if there is no mechanism to constantly monitor
>> filesystem activity during normal operations.  Analogous to
>> filesystem journaling.
>>
>> So - I didn't see anything out there saying "git is fast because it
>> uses inotify" or anything like that.  Perhaps git would not help me
>> at all?  Because git still needs to stat all the files in the tree?
> 
> http://git.or.cz/gitwiki/GitBenchmarks
> 
> While it should be possible to use 'assume unchanged' bit together
> with inotify / icron, it is not something tha is done; IIRC Mercurial
> had Linux-only InotifyPlugin...
>

Well, inotify() is Linux specific, so it'd be quite hard to support on another platform. Emulating it with a billion stat() calls feels rather like a disk (and I/O performance) killer.

-- 
Andreas Ericsson                   andreas.ericsson@op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231