Date: Sun, 4 Jun 2017 10:35:24 +0800 From: Julian Elischer <julian@elischer.org> To: Colin Percival <cperciva@tarsnap.com>, "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Re: Time to increase MAXPHYS? Message-ID: <972dbd34-b5b3-c363-721e-c6e48806e2cd@elischer.org> In-Reply-To: <0100015c6fc1167c-6e139920-60d9-4ce3-9f59-15520276aebb-000000@email.amazonses.com> References: <0100015c6fc1167c-6e139920-60d9-4ce3-9f59-15520276aebb-000000@email.amazonses.com>
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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 */
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