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 */ > > _______________________________________________ > firstname.lastname@example.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscr...@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. -- Allan Jude
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