From 4cbec4c8b9fda9ec784086fe7f74cd32a8adda95 Mon Sep 17 00:00:00 2001 From: Wu Fengguang Date: Tue, 26 Oct 2010 14:21:45 -0700 Subject: [PATCH] writeback: remove the internal 5% low bound on dirty_ratio The dirty_ratio was silently 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 remove 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 thinks it is an aesthetic improvement as well as a functional one :) Signed-off-by: Wu Fengguang Cc: Jan Kara Proposed-by: Con Kolivas Acked-by: Peter Zijlstra Reviewed-by: Rik van Riel Reviewed-by: Neil Brown Reviewed-by: KOSAKI Motohiro Cc: Michael Rubin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fs-writeback.c | 2 +- mm/page-writeback.c | 16 +++++----------- 2 files changed, 6 insertions(+), 12 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index ab38fef1c9a1..97d2951bd4d1 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -582,7 +582,7 @@ static inline bool over_bground_thresh(void) 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); } /* diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 4dd91f7fd39f..b840afa89761 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty) 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 address_space *mapping, * 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 address_space *mapping, * 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;