Messages in this thread Patch in this message | | | Date | Sun, 29 Aug 2010 08:19:17 +0800 | From | Wu Fengguang <> | Subject | [PATCH v2] writeback: remove the internal 5% low bound on dirty_ratio |
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The dirty_ratio was siliently limited in global_dirty_limits() to >= 5%. This is not a user expected behavior. And it's inconsistent with calc_period_shift(), which uses the plain vm_dirty_ratio value.
Let's rip the internal bound.
At the same time, fix balance_dirty_pages() to work with the dirty_thresh=0 case. This allows applications to proceed when dirty+writeback pages are all cleaned.
And ">" fits with the name "exceeded" better than ">=" does. Neil think it is an aesthetic improvement as well as a functional one :)
v2: convert the background writeback checks, too. Just to be sure.
CC: Jan Kara <jack@suse.cz> Proposed-by: Con Kolivas <kernel@kolivas.org> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Reviewed-by: Rik van Riel <riel@redhat.com> Reviewed-by: Neil Brown <neilb@suse.de> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> --- fs/fs-writeback.c | 2 +- mm/page-writeback.c | 16 +++++----------- 2 files changed, 6 insertions(+), 12 deletions(-)
--- linux-next.orig/mm/page-writeback.c 2010-08-29 08:10:30.000000000 +0800 +++ linux-next/mm/page-writeback.c 2010-08-29 08:12:08.000000000 +0800 @@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long * if (vm_dirty_bytes) dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); - else { - int dirty_ratio; - - dirty_ratio = vm_dirty_ratio; - if (dirty_ratio < 5) - dirty_ratio = 5; - dirty = (dirty_ratio * available_memory) / 100; - } + else + dirty = (vm_dirty_ratio * available_memory) / 100; if (dirty_background_bytes) background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); @@ -510,7 +504,7 @@ static void balance_dirty_pages(struct a * catch-up. This avoids (excessively) small writeouts * when the bdi limits are ramping up. */ - if (nr_reclaimable + nr_writeback < + if (nr_reclaimable + nr_writeback <= (background_thresh + dirty_thresh) / 2) break; @@ -542,8 +536,8 @@ static void balance_dirty_pages(struct a * the last resort safeguard. */ dirty_exceeded = - (bdi_nr_reclaimable + bdi_nr_writeback >= bdi_thresh) - || (nr_reclaimable + nr_writeback >= dirty_thresh); + (bdi_nr_reclaimable + bdi_nr_writeback > bdi_thresh) + || (nr_reclaimable + nr_writeback > dirty_thresh); if (!dirty_exceeded) break; --- linux-next.orig/fs/fs-writeback.c 2010-08-29 08:12:51.000000000 +0800 +++ linux-next/fs/fs-writeback.c 2010-08-29 08:12:53.000000000 +0800 @@ -574,7 +574,7 @@ static inline bool over_bground_thresh(v global_dirty_limits(&background_thresh, &dirty_thresh); return (global_page_state(NR_FILE_DIRTY) + - global_page_state(NR_UNSTABLE_NFS) >= background_thresh); + global_page_state(NR_UNSTABLE_NFS) > background_thresh); } /*
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