On 02/10/2011 01:30 AM, Jan Kara wrote: > On Sun 06-02-11 19:54:37, Boaz Harrosh wrote: >> On 02/04/2011 03:38 AM, Jan Kara wrote: >>> The basic idea (implemented in the third patch) is that processes throttled >>> in balance_dirty_pages() wait for enough IO to complete. The waiting is >>> implemented as follows: Whenever we decide to throttle a task in >>> balance_dirty_pages(), task adds itself to a list of tasks that are throttled >>> against that bdi and goes to sleep waiting to receive specified amount of page >>> IO completions. Once in a while (currently HZ/10, in patch 5 the interval is >>> autotuned based on observed IO rate), accumulated page IO completions are >>> distributed equally among waiting tasks. >>> >>> This waiting scheme has been chosen so that waiting time in >>> balance_dirty_pages() is proportional to >>> number_waited_pages * number_of_waiters. >>> In particular it does not depend on the total number of pages being waited for, >>> thus providing possibly a fairer results. >>> >>> I gave the patches some basic testing (multiple parallel dd's to a single >>> drive) and they seem to work OK. The dd's get equal share of the disk >>> throughput (about 10.5 MB/s, which is nice result given the disk can do >>> about 87 MB/s when writing single-threaded), and dirty limit does not get >>> exceeded. Of course much more testing needs to be done but I hope it's fine >>> for the first posting :). >> >> So what is the disposition of Wu's patches in light of these ones? >> * Do they replace Wu's, or Wu's just get rebased ontop of these at a >> later stage? > They are meant as a replacement. > >> * Did you find any hard problems with Wu's patches that delay them for >> a long time? > Wu himself wrote that the current patchset probably won't fly because it > fluctuates too much. So he decided to try to rewrite patches from per-bdi > limits to global limits when he has time... > >> * Some of the complicated stuff in Wu's patches are the statistics and >> rate control mechanics. Are these the troubled area? Because some of >> these are actually some things that I'm interested in, and that appeal >> to me the most. > Basically yes, this logic seems to be the problematic one. > > Honza Thanks dear Jan for you reply. I would love to talk about all this in LSF, and other writeback issues. Keep us posted with results of of your investigations. Cheers Boaz -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
