On 19 December 2014 at 18:55, Branko Čibej <[email protected]> wrote: > 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. :) > Will do!
> FWIW, committing to APR trunk isn't enough: should be back-ported to 1.6 > and 1.5, too. > Yes, you are right. We need this to be backported to 1.6 and 1.5 APR branches. -- Ivan Zhakov
