On 19.12.2014 15:37, Ivan Zhakov wrote: > Originally FSFS caching implementation was using apr_thread_mutex_t to > serialize access to shared data. In r1346122 [1] implementation was > switched to apr_thread_rw_lock_t to improve performance. This change > was released in Subversion 1.8.0 > > Unfortunately current apr_thread_rwlock_t implementation is very slow > on Windows. As quick workaround FSFS code was patched to select > apr_thread_mutex_t or apr_thread_rwlock_t() depending of platform on > compile time (r1611380 [2]). > > In further investigation Bert found why apr_thread_rwlock_t() so slow > on Windows: implementation uses kernel level mutex object instead of > lightweight critical section (critical sections are also used in > apr_thread_mutex_t in most cases). > > The simple patch to switch apr_thread_rwlock_t() implementation to use > critical sections (through apr_thread_mutex_t) was proposed on APR > development mailing list [3], but patch was not commited nor reviewed. > > So the current situation is: > 1. APR has performance problem on Windows that hurts Subversion 1.8.x and > trunk > 2. Subversion trunk has workaround for this specific problem at compile time > 3. Patch proposed to APR mailing list, without any reaction for three months > > From my point of view the proposed patch is straightforward and Bert > stated that it makes apr_thread_rwlock_t 10 to 140 times more > efficient on Windows. So the best option will be to commit Bert's > patch, but I cannot do this since I'm not APR committer :( > > Thoughts?
Thanks for the reminder ... I remember that thread on apr-dev, but it slipped my mind. If I don't review and commit Bert's patch in the next week or so, feel free to send another nagging e-mail. :) FWIW, committing to APR trunk isn't enough: should be back-ported to 1.6 and 1.5, too. -- Brane
