On 13 February 2014 23:40, Stefan Fuhrmann <stefan.fuhrm...@wandisco.com> wrote: > On Thu, Feb 13, 2014 at 7:55 PM, Ivan Zhakov <i...@visualsvn.com> wrote: >> >> On 13 February 2014 22:24, <stef...@apache.org> wrote: >> > Author: stefan2 >> > Date: Thu Feb 13 18:24:17 2014 >> > New Revision: 1567996 >> > >> > URL: http://svn.apache.org/r1567996 > > >> >> > +/* Count a hit in ENTRY within CACHE. >> >> > + */ >> > +static void >> > +increment_hit_counters(svn_membuffer_t *cache, entry_t *entry) >> > +{ >> > + /* To minimize the memory footprint of the cache index, we limit >> > local >> > + * hit counters to 32 bits. These may overflow and we must make sure >> > that >> > + * the global sums are still (roughly due to races) the sum of all >> > local >> > + * counters. */ >> > + if (++entry->hit_count == 0) >> > + cache->hit_count -= APR_UINT32_MAX; >> > + else >> > + cache->hit_count++; >> > + >> As far I understand this counters are updated from several threads >> without mutex? > > > That is correct. > >> >> In that case we have to use atomic functions to >> increment them, otherwise we may skip hit_count == 0 in some cases. > > > No.
> Assuming that the system does not split 32 bit read nor write operation I really, really don't like such assumptions in Subversion code. APR and OS already provides functions for proper inter process manipulations and we must use them, instead of saving several cycles. -- Ivan Zhakov CTO | VisualSVN | http://www.visualsvn.com
