Hi, I have retested kbuild test on a bare HW (8CPUs, 1GB RAM limited by mem=1G, 2GB swap partition). There are 2 groups (A, B) without any hard limit and group A has soft limit set to 700M (to have 70% of available memory). Build starts after fresh boot by extracting sources and make -j4 vmlinux. Each group works on a separate source tree. I have repeated the test 3 times: First some data as returned by /usr/bin/time -v: * Patched: A: User time (seconds): 1133.06 User time (seconds): 1132.84 User time (seconds): 1135.37 Avg: 1133.76 System time (seconds): 258.02 System time (seconds): 259.33 System time (seconds): 258.83 Avg: 258.73 Elapsed (wall clock) time (h:mm:ss or m:ss): 8:57.55 Elapsed (wall clock) time (h:mm:ss or m:ss): 8:55.68 Elapsed (wall clock) time (h:mm:ss or m:ss): 8:50.96 Avg: 08:54.73 B: User time (seconds): 1149.22 User time (seconds): 1153.98 User time (seconds): 1150.37 Avg: 1151.19 (101.5% of A) System time (seconds): 262.13 System time (seconds): 263.31 System time (seconds): 260.84 Avg: 262.09 (101.3% of A) Elapsed (wall clock) time (h:mm:ss or m:ss): 10:13.37 Elapsed (wall clock) time (h:mm:ss or m:ss): 10:17.15 Elapsed (wall clock) time (h:mm:ss or m:ss): 10:05.23 Avg: 10:11.92 (114.4% of A) * Base: A: User time (seconds): 1132.58 User time (seconds): 1140.63 User time (seconds): 1135.68 avg: 1136.30 (100.2% of A - patched) System time (seconds): 264.88 System time (seconds): 263.54 System time (seconds): 261.99 avg: 263.47 (101.8 of A - patched) Elapsed (wall clock) time (h:mm:ss or m:ss): 9:48.54 Elapsed (wall clock) time (h:mm:ss or m:ss): 9:50.44 Elapsed (wall clock) time (h:mm:ss or m:ss): 9:44.28 avg: 09:47.75 (109.9% of A - patched) B: User time (seconds): 1138.32 User time (seconds): 1135.70 User time (seconds): 1136.80 avg: 1136.94 (100.2% of A - patched) System time (seconds): 261.56 System time (seconds): 262.10 System time (seconds): 262.24 avg: 261.97 (100% of A - patched) Elapsed (wall clock) time (h:mm:ss or m:ss): 9:39.17 Elapsed (wall clock) time (h:mm:ss or m:ss): 9:46.95 Elapsed (wall clock) time (h:mm:ss or m:ss): 9:44.73 avg: 09:47.75 (109.1% of A - patched) While for the patched kernel soft limit helped to protect A's working set so it was faster (14% in the total time) than B without any limits. The unpatched kernel has treated them more or less equally regardless the softlimit setting. If we compare patched and base kernels numbers then the overall situation improved slightly (A+B Elapsed time is 2% smaller) with the patched kernel which was quite surprising for me. Maybe a side effect of priority-0 soft reclaim in the base kernel. As the variance between runs wasn't very high I have focused on the first run for the memory usage and reclaim statistics comparisons between the base and patched kernels. * Patched: pgscan_direct_dma32 252408 pgscan_kswapd_dma32 988928 pgsteal_direct_dma32 63565 pgsteal_kswapd_dma32 905223 * Base: pgscan_direct_dma32 97310 (38% of patched) pgscan_kswapd_dma32 1702971 (172%) pgsteal_direct_dma32 83377 (131%) pgsteal_kswapd_dma32 1534616 (169.5%) So it seems that we scanned much more on the patched kernel during the direct reclaim but we have reclaimed less nevertheless. This is most probably because there is a bigger pressure on B's LRU and we encounter more dirty pages so more pages are scanned in the end. In sum we scanned and reclaimed less (by 45% resp. 67%) though. You can find some graphs at: - http://labs.suse.cz/mhocko/soft_limit_rework/base-usage.png - http://labs.suse.cz/mhocko/soft_limit_rework/patched-usage.png Per group charges over time. - http://labs.suse.cz/mhocko/soft_limit_rework/base-usage-histogram.png - http://labs.suse.cz/mhocko/soft_limit_rework/patched-usage-histogram.png Same here but in the histogram form to see the main tendencies. - http://labs.suse.cz/mhocko/soft_limit_rework/pgscan.png - http://labs.suse.cz/mhocko/soft_limit_rework/pgsteal.png Scanning and reclaiming activity comparision between the base and the patched kernel. -- Michal Hocko SUSE Labs -- 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>
