Re: diffcore-rename performance mode

From: David Kastrup <dak@gnu.org>
Date: Sep 25, 2007, 19:32 UTC
Message-ID: <86641y4k34.fsf@lola.quinscape.zz>
In-Reply-To: <20070925190640.GA4613@coredump.intra.peff.net>

Jeff King <peff@peff.net> writes:

Show 20 quoted lines

> On Tue, Sep 25, 2007 at 12:38:43PM -0400, Jeff King wrote:
>
>>[...]
>>
>> What is most confusing is why the 'somefree' case performs so badly,
>> since we should just be using the cnt_data. I'll see if gprof can shed
>
> OK, I found the problem. estimate_similarity calls
> diff_populate_filespec each time, even if we already have the cnt_data,
> which leads to recomputing the blob contents from deltas. Oops.
>
> Fixing this, the correct numbers are:
>
>                  | stock | nofree | old somefree | fixed somefree
> -----------------|-----------------------------------------------
> user time (s)    | 76.78 | 16.96  | 46.26        | 16.99
> peak memory (Kb) | 52300 | 66796  | 59156        | 57328
>
> So now we're at a 4.5x speedup for about 10% extra memory usage. Patch
> will follow.

Sounds good except when we happen to just hit the "memory working set exceeds physical memory" sweet spot. But the odds are much better than for "nofree".

-- 
David Kastrup