* Peter Zijlstra <peterz@xxxxxxxxxxxxx> [2010-08-18 11:58:56]: > On Wed, 2010-08-18 at 14:52 +0530, Nikanth Karthikesan wrote: > > On Tuesday 17 August 2010 13:54:35 Peter Zijlstra wrote: > > > On Tue, 2010-08-17 at 10:39 +0530, Nikanth Karthikesan wrote: > > > > Oh, nice. Per-task limit is an elegant solution, which should help > > > > during most of the common cases. > > > > > > > > But I just wonder what happens, when > > > > 1. The dirtier is multiple co-operating processes > > > > 2. Some app like a shell script, that repeatedly calls dd with seek and > > > > skip? People do this for data deduplication, sparse skipping etc.. > > > > 3. The app dies and comes back again. Like a VM that is rebooted, and > > > > continues writing to a disk backed by a file on the host. > > > > > > > > Do you think, in those cases this might still be useful? > > > > > > Those cases do indeed defeat the current per-task-limit, however I think > > > the solution to that is to limit the amount of writeback done by each > > > blocked process. > > > > > > > Blocked on what? Sorry, I do not understand. > > balance_dirty_pages(), by limiting the work done there (or actually, the > amount of page writeback completions you wait for -- starting IO isn't > that expensive), you can also affect the time it takes, and therefore > influence the impact. > There is an ongoing effort to look at per-cgroup dirty limits and I honestly think it would be nice to do it at that level first. We need it there as a part of the overall I/O controller. As a specialized need it could handle your case as well. -- Three Cheers, Balbir -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>