Messages in this thread | | | Subject | Re: [ltt-dev] [RFC PATCH] block: Fix bio merge induced high I/O latency | From | Ben Gamari <> | Date | Wed, 21 Jan 2009 01:17:45 -0500 |
| |
On Tue, 2009-01-20 at 23:54 -0500, Mathieu Desnoyers wrote: > * Ben Gamari (bgamari@gmail.com) wrote: > > On Tue, Jan 20, 2009 at 7:25 PM, Mathieu Desnoyers > > <mathieu.desnoyers@polymtl.ca> wrote: > > > * Mathieu Desnoyers (mathieu.desnoyers@polymtl.ca) wrote: > > > > > > As a side-note : I'd like to have my results confirmed by others. > > > > Well, I think the (fixed) patch did help to some degree (I haven't > > done fio benchmarks to compare against yet). Unfortunately, the I/O > > wait time problem still remains. I have been waiting 3 minutes now for > > evolution to start with 88% I/O wait time yet no visible signs of > > progress. I've confirmed I'm using the CFQ scheduler, so that's not > > the problem. > > > > Did you also > > echo 1 > /sys/block/sd{a,b}/device/queue_depth I have been using this in some of my measurements (this is recorded, of course).
> echo 1 > /sys/block/sd{a,b}/queue/iosched/slice_async_rq > echo 1 > /sys/block/sd{a,b}/queue/iosched/quantum I haven't been doing this although I will collect a data set with these parameters set. It would be to compare the effect of this to the default configuration.
> > (replacing sd{a,b} with your actual drives) ? > > It seems to have been part of the factors that helped (along with the > patch). > > And hopefully you don't have a recent Seagate hard drive like me ? :-) Thankfully, no.
> > So you test case is : > - start a large dd with 1M block size > - time evolution > I've been using evolution to get a rough idea of the performance of the configurations but not as a benchmark per se. I have some pretty good-sized maildirs, so launching evolution for the first time can be quite a task, IO-wise. Also, switching between folders used to be quite time consuming. It seems like the patch did help a bit on this front though.
For a quantitative benchmark I've been using the fio job that you posted earlier. I've been collecting results and should have a pretty good data set soon.
I'll send out a compilation of all the data I've collected as soon as I've finished.
- Ben
| |