2009/6/14 Kris Kennaway <[email protected]>: > Attilio Rao wrote: >> >> This patch enables adaptive spinning for lockmgr: >> http://www.freebsd.org/~attilio/adaptive_lockmgr.diff >> >> and it should presumably improve performance on disks/vfs/buffer cache >> based benchmarks, so, if you want to try out and report any benchmarks >> result, I'd love to see it. >> Please note that there are some parameters to tune: for example, you >> would like to not enable adaptive spinning to default while you just >> want that for a class of locks (and in that case you want to apply the >> reversed logic for what is living now) or you want to use different >> values for retries and loops. Interested developers can refer to such >> 3 variables. >> Peter Holm alredy tested that patch for about 24hours without any >> regression to report. >> >> Also note that the patch is not 100% yet as long as it needs UPDATES >> and manpages updates, but they will be added just in time before to >> commit. >> The modify is all there. > > I have a vague memory that we had tested a version of this in the past and > found that it caused a performance loss in common cases? Many lockmgr > callers are not amenable to adaptive spinning because they have to wait on > slow I/O. Testing only with e.g. md backing might give results that are > non-representative.
I don't think I ever implemented adaptive spinning in lockmgr so if somebody else did I don't know. Said that, probabilly the best approach would be to disable it by default ad use a LK_ADAPTIVESPIN flag on a per instance basis. Such conditions, though, need to be explored a bit and I have no time to dedicate to this right now. Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-smp To unsubscribe, send any mail to "[email protected]"
