On Thu, Jun 19, 2014 at 02:38:44PM -0400, Jeff Moyer wrote: > Mel Gorman <mgor...@suse.de> writes: > > > The existing CFQ default target_latency results in very poor performance > > for larger numbers of threads doing sequential reads. While this can be > > easily described as a tuning problem for users, it is one that is tricky > > to detect. This patch the default on the assumption that people with access > > to expensive fast storage also know how to tune their IO scheduler. > > > > The following is from tiobench run on a mid-range desktop with a single > > spinning disk. > > > > 3.16.0-rc1 3.16.0-rc1 > > 3.0.0 > > vanilla cfq600 > > vanilla > > Mean SeqRead-MB/sec-1 121.88 ( 0.00%) 121.60 ( -0.23%) > > 134.59 ( 10.42%) > > Mean SeqRead-MB/sec-2 101.99 ( 0.00%) 102.35 ( 0.36%) > > 122.59 ( 20.20%) > > Mean SeqRead-MB/sec-4 97.42 ( 0.00%) 99.71 ( 2.35%) > > 114.78 ( 17.82%) > > Mean SeqRead-MB/sec-8 83.39 ( 0.00%) 90.39 ( 8.39%) > > 100.14 ( 20.09%) > > Mean SeqRead-MB/sec-16 68.90 ( 0.00%) 77.29 ( 12.18%) > > 81.64 ( 18.50%) > > Did you test any workloads other than this? Also, what normal workload > has 8 or more threads doing sequential reads? (That's an honest > question.)
I'd also suggest that making changes basd on the assumption that people affected by the change know how to tune CFQ is a bad idea. When CFQ misbehaves, most people just switch to deadline or no-op because they don't understand how CFQ works, nor what what all the nobs do or which ones to tweak to solve their problem.... Cheers, Dave. -- Dave Chinner da...@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
