On 14/12/2016 21:49, Alexander Motin wrote: > On 14.12.2016 14:03, Andriy Gapon wrote: >> On 08/12/2016 17:58, Alexander Motin wrote: >>> This change switches zio_timestamp_compare() from comparing uninitialized >>> io_offset to really populated io_bookmark values. I haven't decided yet >>> what to do with timestampts, but on simple tests this change gives the >>> same peformance results by just making code to work as declared. >> >> I think that we should just enable precise timestamps. >> I just can't see them noticeably hurting performance given the amount of >> calculations, memory allocations, locking, etc, that ZFS already has. >> And there are layers above and below ZFS too. > > It is orthogonal to this change and can be done any time, if decided.
Yes, indeed. > I worried mostly about some older systems still using HPET or ACPI > timecounters, where half dozen extra timer calls per single I/O may be > quite expensive. > > I've recently reviewed all places where ZFS calls gethrtime(), and found > that in most of them precision is not needed, even 1 second would be > enough, not even 1/hz. I've found only two cases where precision is > important, both about ZIO sorting in different places (this is one of > the two), and both of them are now workarounded now by using offset as > secondary key. Thank you for looking into this and fixing the bug! -- Andriy Gapon _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
