Date: Sat, 3 Jun 2017 20:59:04 +0000 From: Colin Percival <cperciva@tarsnap.com> To: "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Time to increase MAXPHYS? Message-ID: <0100015c6fc1167c-6e139920-60d9-4ce3-9f59-15520276aebb-000000@email.amazonses.com>
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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). -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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