Date: Sun, 4 Jun 2017 17:15:49 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Allan Jude <allanjude@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: Time to increase MAXPHYS? Message-ID: <20170604141549.GC3182@zxy.spb.ru> In-Reply-To: <3719c729-9434-3121-cf52-393a4453d0b2@freebsd.org> References: <0100015c6fc1167c-6e139920-60d9-4ce3-9f59-15520276aebb-000000@email.amazonses.com> <972dbd34-b5b3-c363-721e-c6e48806e2cd@elischer.org> <3719c729-9434-3121-cf52-393a4453d0b2@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sat, Jun 03, 2017 at 11:55:51PM -0400, Allan Jude wrote: > On 2017-06-03 22:35, Julian Elischer wrote: > > On 4/6/17 4:59 am, Colin Percival wrote: > >> On January 24, 1998, in what was later renumbered to SVN r32724, dyson@ > >> wrote: > >>> Add better support for larger I/O clusters, including larger physical > >>> I/O. The support is not mature yet, and some of the underlying > >>> implementation > >>> needs help. However, support does exist for IDE devices now. > >> and increased MAXPHYS from 64 kB to 128 kB. Is it time to increase it > >> again, > >> or do we need to wait at least two decades between changes? > >> > >> This is hurting performance on some systems; in particular, EC2 "io1" > >> disks > >> are optimized for 256 kB I/Os, EC2 "st1" (throughput optimized > >> spinning rust) > >> disks are optimized for 1 MB I/Os, and Amazon's NFS service (EFS) > >> recommends > >> using a maximum I/O size of 1 MB (and despite NFS not being *physical* > >> I/O it > >> seems to still be limited by MAXPHYS). > >> > > We increase it in freebsd 8 and 10.3 on our systems, Only good results. > > > > sys/sys/param.h:#define MAXPHYS (1024 * 1024) /* max raw I/O > > transfer size */ > > > > _______________________________________________ > > freebsd-current@freebsd.org mailing list > > https://lists.freebsd.org/mailman/listinfo/freebsd-current > > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" > > At some point Warner and I discussed how hard it might be to make this a > boot time tunable, so that big amd64 machines can have a larger value > without causing problems for smaller machines. > > ZFS supports a block size of 1mb, and doing I/Os in 128kb negates some > of the benefit. 16MB
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20170604141549.GC3182>