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Re: svn commit: r1611380 - /subversion/trunk/subversion/libsvn_subr/cache-membuffer.c

From: Stefan Fuhrmann <stefan.fuhrmann_at_wandisco.com>
Date: Mon, 22 Dec 2014 21:08:11 +0100

On Mon, Dec 22, 2014 at 1:01 PM, Ivan Zhakov <ivan_at_visualsvn.com> wrote:

> On 17 July 2014 at 18:00, <stefan2_at_apache.org> wrote:
> > Author: stefan2
> > Date: Thu Jul 17 15:00:33 2014
> > New Revision: 1611380
> >
> > URL: http://svn.apache.org/r1611380
> > Log:
> > Work around for the poor performance of APR reader / writer locks on
> Windows.
> > Basically, fall back to 1.7 code on Win32 by using a simple mutex.
> >
> > This resulted in a 35% increase in throughput for a 'null-export' over
> > ra_serf from hot SVN caches with revprop caching enabled. OTOH, this may
> > cost us some scalability with ra_svn on high-speed (>1Gb) networks.
> >
> > * subversion/libsvn_subr/cache-membuffer.c
> > (USE_SIMPLE_MUTEX): New flag. Set depending on whether we need to fall
> > back to a simple locking scheme.
> > (svn_membuffer_t): Select lock type at compile time.
> > (read_lock_cache,
> > write_lock_cache,
> > force_write_lock_cache,
> > unlock_cache): Use the simple mutex lock when selected.
> > (svn_cache__membuffer_cache_create): Initialize the correct lock type
> and
> > disable the counter_mutex if
> redundant.
> >
> > Modified:
> > subversion/trunk/subversion/libsvn_subr/cache-membuffer.c
> >
> [...]
> > @@ -674,6 +712,12 @@ static svn_error_t *
> > unlock_cache(svn_membuffer_t *cache, svn_error_t *err)
> > {
> > #if APR_HAS_THREADS
> > +# if USE_SIMPLE_MUTEX
> > +
> > + return svn_mutex__unlock(cache->lock, SVN_NO_ERROR);
> > +
> > +# else
> > +
> > if (cache->lock)
> > {
> > apr_status_t status = apr_thread_rwlock_unlock(cache->lock);
> > @@ -683,6 +727,8 @@ unlock_cache(svn_membuffer_t *cache, svn
> > if (status)
> > return svn_error_wrap_apr(status, _("Can't unlock cache mutex"));
> > }
> > +
> > +# endif
> > #endif
> > return err;
> > }
> The provided ERR argument is ignored in USE_SIMPLE_MUTEX codepath. So
> any error from cache serializer will be ignored and invalid result
> will be used.
>

Thanks for fixing!

-- Stefan^2.
Received on 2014-12-22 21:10:10 CET

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