subversion-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Daniel Shahaf <...@daniel.shahaf.name>
Subject Re: svn commit: r1040663 - in /subversion/trunk/subversion/libsvn_wc: wc-queries.sql wc_db.c
Date Wed, 01 Dec 2010 13:29:14 GMT
Julian Foad wrote on Wed, Dec 01, 2010 at 13:06:04 +0000:
> Daniel Shahaf wrote:
> > So we loop over the remaining sha1's and remove each of them...
> > I wonder if there is room for further optimization here?  e.g., does
> > this prepare/reset the statement just once, or once per iteration?
> 
> Each iteration of this loop prepares, uses and resets a SQL statement,
> and also removes a pristine file from disk.  So yes there is room for
> further optimization of the SQL part of that.
> 

Thanks for the overview.

> The main concern I was addressing was that the previous method was
> *quadratic* in the total number of pristines in the store, because for
> each one in the store it would scan the NODES and ACTUAL_NODE tables
> looking for a reference to it.  I had noticed that even a no-op cleanup
> took a very long time on a large WC.  It will help if I show some real
> timings.
> 
> Wall clock times for "svn cleanup" on a clean checkout of
> ^/subversion/branches@1040943 on my Linux system.
> 
>   r1040662 build: first time = 15 minutes, second = 14.8 minutes.
> 
>   r1040663 build: first time = 4.4s, best of many repetitions = 0.7s.
> 


:-)!

> Now the algorithm is only linear time, which is a *huge* win.  A
> 'cleanup' operation doesn't need to be blisteringly fast, so I don't
> think it needs more optimisation.
> 
> I've edited the log message to clarify the main point, and to point out
> the big-WC timing improvement.
> 

Fair enough; let's table this additional optimization for now.  We can
always add it later if needed (i.e., if the time spent removing
unreferenced pristines should become an issue).

> - Julian
> 
> 
> # r1040662 build
> $ time ~/build/subversion-c/subversion/svn/svn cleanup branches/
> real	15m4.962s
> user	9m0.306s
> sys	6m3.967s
> 
> # r1040663 build
> $ time ~/build/subversion-c/subversion/svn/svn cleanup branches/
> real	0m0.708s
> user	0m0.436s
> sys	0m0.212s
> 
> 
> 

Thanks,

Daniel


Mime
View raw message