On Fri, Jan 22, 2016 at 12:28:10AM +1000, Nalorokk wrote: > It appears that kernels newer than 4.1 have kswapd-related bug resulting in > high CPU usage. CPU 100% usage could last for several minutes or several > days, with CPU being busy entirely with serving kswapd. It happens usually > after server being mostly idle, sometimes after days, sometimes after weeks > of uptime. But the issue appears much sooner if the machine is loaded with > something like building a kernel. > > Here are the graphs of CPU load: first > <http://i.piccy.info/i9/9ee6c0620c9481a974908484b2a52a0f/1453384595/44012/994698/cpu_month.png>, > second > <http://i.piccy.info/i9/7c97c2f39620bb9d7ea93096312dbbb6/1453384649/41222/994698/cpu_year.png>. > Perf top output is here <http://pastebin.com/aRzTjb2x>as well. > > To find the cause of this problem I've started with the fact that the issue > appeared after 4.1 kernel update. Then I performed longterm test of 3.18, > and discovered that 3.18 is unaffected by this bug. Then I did some tests > of 4.0 to confirm that this version behaves well too. > > Then I performed git bisect from tag v4.0 to v4.1-rc1 and found exact > commits that seem to be reason of high CPU usage. > > The first really "bad" commit is 79553da293d38d63097278de13e28a3b371f43c1. > 2 previous commits cause weird behavior as well resulting in kswapd > consuming more CPU than unaffected kernels, but not that much as the commit > pointed above. I believe those commits are related to the same mm tree > merge. > > I tried to add transparent_hugepage=never to kernel boot parameters, but it > did not change anything. Changing allocator to SLAB from SLUB alters > behavior and makes CPU load lower, but don't solve a problem at all. > > Here <https://bugzilla.kernel.org/show_bug.cgi?id=110501>is kernel bugzilla > bugreport as well. > > Ideas? Could you try to insert "late_initcall(set_recommended_min_free_kbytes);" back and check if makes any difference. -- Kirill A. Shutemov -- 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>
