On 12 March 2013 03:15, Hillf Danton <dhillf@xxxxxxxxx> wrote: >>On 11 March 2013 13:15, Michal Suchanek <hramrach@xxxxxxxxx> wrote: >>>On 8 February 2013 17:31, Michal Suchanek <hramrach@xxxxxxxxx> wrote: >>> Hello, >>> >>> I am dealing with VM disk images and performing something like wiping >>> free space to prepare image for compressing and storing on server or >>> copying it to external USB disk causes >>> >>> 1) system lockup in order of a few tens of seconds when all CPU cores >>> are 100% used by system and the machine is basicaly unusable >>> >>> 2) oom killer killing processes >>> >>> This all on system with 8G ram so there should be plenty space to work with. >>> >>> This happens with kernels 3.6.4 or 3.7.1 >>> >>> With earlier kernel versions (some 3.0 or 3.2 kernels) this was not a >>> problem even with less ram. >>> >>> I have vm.swappiness = 0 set for a long time already. >>> >>> >>I did some testing with 3.7.1 and with swappiness as much as 75 the >>kernel still causes all cores to loop somewhere in system when writing >>lots of data to disk. >> >>With swappiness as much as 90 processes still get killed on large disk writes. >> >>Given that the max is 100 the interval in which mm works at all is >>going to be very narrow, less than 10% of the paramater range. This is >>a severe regression as is the cpu time consumed by the kernel. >> >>The io scheduler is the default cfq. >> >>If you have any idea what to try other than downgrading to an earlier >>unaffected kernel I would like to hear. >> > Can you try commit 3cf23841b4b7(mm/vmscan.c: avoid possible > deadlock caused by too_many_isolated())? > > Or try 3.8 and/or 3.9, additionally? Hello, in the meantime I tried setting io scheduler to deadline because I remember using that one in my self-built kernels due to cfq breaking some obscure block driver. With the deadline io scheduler I can set swappiness back to 0 and the system works normally even for moderate amount of IO - restoring disk images from network. This would cause lockups and oom killer running loose with the cfq scheduler. So I guess I found what breaks the system and it is not so much the kernel version. It's using pre-built kernels with the default scheduler. Thanks Michal -- 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>