On Mon, Nov 12, 2012 at 11:35:28AM -0800, Sonny Rao wrote: > The system uses global_dirtyable_memory() to calculate > number of dirtyable pages/pages that can be allocated > to the page cache. A bug causes an underflow thus making > the page count look like a big unsigned number. This in turn > confuses the dirty writeback throttling to aggressively write > back pages as they become dirty (usually 1 page at a time). > > Fix is to ensure there is no underflow while doing the math. > > Signed-off-by: Sonny Rao <sonnyrao@xxxxxxxxxxxx> > Signed-off-by: Puneet Kumar <puneetster@xxxxxxxxxxxx> Thanks for debugging and sending in the patch. It might be useful to note in the changelog that the crawling writeback problem only affects highmem systems because of the way the underflowed count of high memory is subtracted from the overall amount of dirtyable memory. And that the problem was introduced with v3.2-4896-gab8fabd (which means that we should include Cc: stable@xxxxxxxxxx for 3.3+). The diff itself looks good to me, thanks again: Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> -- 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>