Date: Thu, 15 Dec 2016 12:48:07 +0200 From: Andriy Gapon <avg@FreeBSD.org> To: Alexander Motin <mav@FreeBSD.org>, src-committers@FreeBSD.org, svn-src-all@FreeBSD.org, svn-src-head@FreeBSD.org Subject: Re: svn commit: r309714 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs Message-ID: <94544782-cfcc-86ee-da17-bc6b25873313@FreeBSD.org> In-Reply-To: <eaaef2a9-eb5a-5629-c8f3-54c3a45b16b5@FreeBSD.org> References: <201612081558.uB8Fw4xA027508@repo.freebsd.org> <cd831c65-ffb3-b84b-7e0e-b84ae32bace1@FreeBSD.org> <eaaef2a9-eb5a-5629-c8f3-54c3a45b16b5@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
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
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?94544782-cfcc-86ee-da17-bc6b25873313>