On 10/18/2010 03:55 PM, Mel Gorman wrote: > On Thu, Oct 14, 2010 at 05:28:33PM +0200, Christian Ehrhardt wrote: > >> Seing the patches Mel sent a few weeks ago I realized that this series >> might be at least partially related to my reports in 1Q 2010 - so I ran my >> testcase on a few kernels to provide you with some more backing data. > > Thanks very much for revisiting this. > >> Results are always the average of three iozone runs as it is known to be somewhat noisy - especially when affected by the issue I try to show here. >> As discussed in detail in older threads the setup uses 16 disks and scales the number of concurrent iozone processes. >> Processes are evenly distributed so that it always is one process per disk. >> In the past we reported 40% to 80% degradation for the sequential read case based on 2.6.32 which can still be seen. >> What we found was that the allocations for page cache with GFP_COLD flag loop a long time between try_to_free, get_page, reclaim as free makes some progress and due to that GFP_COLD allocations can loop and retry. >> In addition my case had no writes at all, which forced congestion_wait to wait the full timeout all the time. >> >> Kernel (git) 4 8 16 deviation #16 case comment >> linux-2.6.30 902694 1396073 1892624 base base >> linux-2.6.32 752008 990425 932938 -50.7% impact as reported in 1Q 2010 >> linux-2.6.35 63532 71573 64083 -96.6% got even worse >> linux-2.6.35.6 176485 174442 212102 -88.8% fixes useful, but still far away >> linux-2.6.36-rc4-trace 119683 188997 187012 -90.1% still bad >> linux-2.6.36-rc4-fix 884431 1114073 1470659 -22.3% Mels fixes help a lot! >> [...] > If all goes according to plan, > kernel 2.6.37-rc1 will be of interest. Thanks again. Here a measurement with 2.6.37-rc1 as confirmation of progress: linux-2.6.37-rc1 876588 1161876 1643430 -13.1% even better than 2.6.36-fix That means 2.6.37-rc1 really shows what we hoped for. And it eventually even turned out a little bit better than 2.6.36 + your fixes. -- Grüsse / regards, Christian Ehrhardt IBM Linux Technology Center, System z Linux Performance -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>