Date: Fri, 15 Sep 2017 09:20:05 -0600 From: Warner Losh <imp@bsdimp.com> To: Nikolai Lifanov <lifanov@freebsd.org> Cc: Allan Jude <allanjude@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Time to increase MAXPHYS? Message-ID: <CANCZdfpmznLHkF3erDQVcr4THJjQHaj5caWVkuNF7d1z7b9Z%2BA@mail.gmail.com> In-Reply-To: <bdcfce17-4cbf-70d0-c78b-a73b0dfde648@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> <bdcfce17-4cbf-70d0-c78b-a73b0dfde648@FreeBSD.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, Sep 15, 2017 at 9:18 AM, Nikolai Lifanov <lifanov@freebsd.org> wrote: > On 6/3/17 11:55 PM, 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. > > > > I am preparing some benchmarks and other data along with a patch to > > increase the maximum size of pipe I/O's as well, because using 1MB > > offers a relatively large performance gain there as well. > > > > Hi! > > I also migrated to 1mb recordsize. What's the status of your patches > and/or making MAXPHYS a boot-time tunable? I can help test these. > Still in my queue to do. Warner
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CANCZdfpmznLHkF3erDQVcr4THJjQHaj5caWVkuNF7d1z7b9Z%2BA>