On 01/17/2014 04:12 PM, riel@xxxxxxxxxx wrote: > From: Rik van Riel <riel@xxxxxxxxxx> > > The current code in task_numa_placement calculates the difference > between the old and the new value, but also temporarily stores half > of the old value in the per-process variables. > > The NUMA balancing code looks at those per-process variables, and > having other tasks temporarily see halved statistics could lead to > unwanted numa migrations. This can be avoided by doing all the math > in local variables. > > This change also simplifies the code a little. I am seeing what looks like a performance improvement with this patch, so it is not just a theoretical bug. The improvement is small, as is to be expected with such a small race, but with two 32-warehouse specjbb instances on a 4-node, 10core/20thread per node system, I see the following change in performance, and reduced numa page migrations. Without the patch: run 1: throughput 367660 367660, migrated 3112982 run 2: throughput 353821 355612, migrated 2881317 run 3: throughput 355027 355027, migrated 3358105 run 4: throughput 354366 354366, migrated 3466687 run 5: throughput 356186 356186, migrated 3152194 run 6: throughput 361431 361431, migrated 3336219 run 7: throughput 354704 354704, migrated 3345418 run 8: throughput 363770 363770, migrated 3642925 run 9: throughput 363380 363380, migrated 3192836 run 10: throughput 358440 358440, migrated 3354028 avg: througphut 358968, migrated 3284271 With the patch: run 1: throughput 360580 360580, migrated 3169872 run 2: throughput 361303 361303, migrated 3220280 run 3: throughput 367692 367692, migrated 3096093 run 4: throughput 362320 362320, migrated 2981762 run 5: throughput 364201 364201, migrated 3089107 run 6: throughput 364561 364561, migrated 2892364 run 7: throughput 360771 360771, migrated 3086638 run 8: throughput 361530 361530, migrated 2933256 run 9: throughput 365841 365841, migrated 3356944 run 10: throughput 359188 359188, migrated 3394545 avg: througphut 362798, migrated 3122086 -- All rights reversed -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>