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

From: Ivan Zhakov <ivan_at_visualsvn.com>
Date: Mon, 22 Dec 2014 15:01:10 +0300

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.

-- 
Ivan Zhakov
Received on 2014-12-22 13:03:36 CET

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