From: James Pickens <jepicken@gmail.com>
Date: Fri, 19 Dec 2008 01:04:29 GMT
Subject: Re: [RFC PATCH 0/2] Add support for multi threaded checkout
Message-ID: <885649360812181704l3a905ebfrb90f391e86004efc@mail.gmail.com>
In-Reply-To: <494ABDC9.9060001@morey-chaisemartin.com>

On Thu, Dec 18, 2008, Nicolas Morey-Chaisemartin
<devel@morey-chaisemartin.com> wrote:
> I guess you could do something like :
>
> #define checkout_lock()         core_threaded_checkout ?pthread_mutex_lock(&checkout_mutex) : (void) 0
> #define checkout_unlock()               core_threaded_checkout ?pthread_mutex_unlock(&checkout_mutex) : (void) 0

I tried that, and to make it easier to see the impact, I changed the
'wrote = write_in_full(...)' calls in entry.c to 'wrote = size'.  That
makes git just create a bunch of empty files instead of writing the real
contents to disk.  Here's the result, with core.threadedcheckout set to
false, best of 2 runs:

original patch:     3.19
original + above:   3.18

So the cost of locking/unlocking the mutex looks vanishingly small in the
single thread case.

This also puts an upper bound on the time required for a single thread to
unpack the data.

James