On Sat, 2009-10-03 at 08:40 -0400, Vivek Goyal wrote: > On Sat, Oct 03, 2009 at 07:29:15AM -0400, Vivek Goyal wrote: > > On Sat, Oct 03, 2009 at 07:56:18AM +0200, Mike Galbraith wrote: > > > On Sat, 2009-10-03 at 07:49 +0200, Mike Galbraith wrote: > > > > On Fri, 2009-10-02 at 20:19 +0200, Jens Axboe wrote: > > > > > > > > > If you could do a cleaned up version of your overload patch based on > > > > > this: > > > > > > > > > > http://git.kernel.dk/?p=linux-2.6-block.git;a=commit;h=1d2235152dc745c6d94bedb550fea84cffdbf768 > > > > > > > > > > then lets take it from there. > > > > > > > > Note to self: build the darn thing after last minute changes. > > > > > > Block: Delay overloading of CFQ queues to improve read latency. > > > > > > Introduce a delay maximum dispatch timestamp, and stamp it when: > > > 1. we encounter a known seeky or possibly new sync IO queue. > > > 2. the current queue may go idle and we're draining async IO. > > > 3. we have sync IO in flight and are servicing an async queue. > > > 4 we are not the sole user of disk. > > > Disallow exceeding quantum if any of these events have occurred recently. > > > > > > > So it looks like primarily the issue seems to be that we done lot of > > dispatch from async queue and if some sync queue comes in now, it will > > experience latencies. > > > > For a ongoing seeky sync queue issue will be solved up to some extent > > because previously we did not choose to idle for that queue now we will > > idle, hence async queue will not get a chance to overload the dispatch > > queue. > > > > For the sync queues where we choose not to enable idle, we still will see > > the latencies. Instead of time stamping on all the above events, can we > > just keep track of last sync request completed in the system and don't > > allow async queue to flood/overload the dispatch queue with-in certain > > time limit of that last sync request completion. This just gives a buffer > > period to that sync queue to come back and submit more requests and > > still not suffer large latencies? > > > > Thanks > > Vivek > > > > Hi Mike, > > Following is a quick hack patch for the above idea. It is just compile and > boot tested. Can you please see if it helps in your scenario. Box sends hugs and kisses. s/desktop/latency and ship 'em :) perf stat 1.70 1.94 1.32 1.89 1.87 1.7 fairness=1 overload_delay=1 1.55 1.79 1.38 1.53 1.57 1.5 desktop=1 +last_end_sync perf stat testo.sh Avg 108.12 106.33 106.34 97.00 106.52 104.8 1.000 fairness=0 overload_delay=0 93.98 102.44 94.47 97.70 98.90 97.4 .929 fairness=0 overload_delay=1 90.87 95.40 95.79 93.09 94.25 93.8 .895 fairness=1 overload_delay=0 89.93 90.57 89.13 93.43 93.72 91.3 .871 fairness=1 overload_delay=1 89.81 88.82 91.56 96.57 89.38 91.2 .870 desktop=1 +last_end_sync -Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
