On Thu, Sep 24, 2009 at 11:38:16PM +0800, Peter Zijlstra wrote: > On Thu, 2009-09-24 at 16:33 +0800, Wu Fengguang wrote: > > > Yeah, FIFO queuing should be good enough. > > > > I'd like to propose one more data structure for evaluation :) > > > > - bdi->throttle_lock > > - bdi->throttle_list pages to sync for each waiting task, taken from sync_writeback_pages() > > - bdi->throttle_pages (counted down) pages to sync for the head task, shall be atomic_t > > > > In balance_dirty_pages(), it would do > > > > nr_to_sync = sync_writeback_pages() > > if (list_empty(bdi->throttle_list)) # I'm the only task > > bdi->throttle_pages = nr_to_sync > > append nr_to_sync to bdi->throttle_list > > kick off background writeback > > wait > > remove itself from bdi->throttle_list and wait list > > set bdi->throttle_pages for new head task (or LONG_MAX) > > > > In __bdi_writeout_inc(), it would do > > > > if (--bdi->throttle_pages <= 0) > > check and wake up head task > > > > In wb_writeback(), it would do > > > > if (args->for_background && exiting) > > wake up all throttled tasks > > To prevent wake up too many tasks at the same time, it can relax the > > background threshold a bit, so that __bdi_writeout_inc() become the > > only wake up point in normal cases. > > > > if (args->for_background && !list_empty(bdi->throttle_list) && > > over background_thresh - background_thresh / 32) > > keep write pages; I realized this last change is not necessary, because we already have a big enough buffer area: (dirty_thresh + background_thresh)/2 ==> background_thresh > Right, something like that ought to work well, or at least sounds like > worth a try ;-) Thanks :) -- 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
