From 8311c29d40235062a843f4a8e8a70a44af6fe4c9 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 4 Mar 2008 14:29:30 -0800 Subject: [PATCH] md: reduce CPU wastage on idle md array with a write-intent bitmap On an md array with a write-intent bitmap, a thread wakes up every few seconds and scans the bitmap looking for work to do. If the array is idle, there will be no work to do, but a lot of scanning is done to discover this. So cache the fact that the bitmap is completely clean, and avoid scanning the whole bitmap when the cache is known to be clean. Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/md/bitmap.c | 19 +++++++++++++++++-- include/linux/raid/bitmap.h | 2 ++ 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c index 7aeceedcf7d4..831aed9c56ff 100644 --- a/drivers/md/bitmap.c +++ b/drivers/md/bitmap.c @@ -1047,6 +1047,11 @@ void bitmap_daemon_work(struct bitmap *bitmap) if (time_before(jiffies, bitmap->daemon_lastrun + bitmap->daemon_sleep*HZ)) return; bitmap->daemon_lastrun = jiffies; + if (bitmap->allclean) { + bitmap->mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT; + return; + } + bitmap->allclean = 1; for (j = 0; j < bitmap->chunks; j++) { bitmap_counter_t *bmc; @@ -1068,8 +1073,10 @@ void bitmap_daemon_work(struct bitmap *bitmap) clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE); spin_unlock_irqrestore(&bitmap->lock, flags); - if (need_write) + if (need_write) { write_page(bitmap, page, 0); + bitmap->allclean = 0; + } continue; } @@ -1098,6 +1105,9 @@ void bitmap_daemon_work(struct bitmap *bitmap) /* if (j < 100) printk("bitmap: j=%lu, *bmc = 0x%x\n", j, *bmc); */ + if (*bmc) + bitmap->allclean = 0; + if (*bmc == 2) { *bmc=1; /* maybe clear the bit next time */ set_page_attr(bitmap, page, BITMAP_PAGE_CLEAN); @@ -1132,6 +1142,8 @@ void bitmap_daemon_work(struct bitmap *bitmap) } } + if (bitmap->allclean == 0) + bitmap->mddev->thread->timeout = bitmap->daemon_sleep * HZ; } static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap, @@ -1226,6 +1238,7 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect sectors -= blocks; else sectors = 0; } + bitmap->allclean = 0; return 0; } @@ -1296,6 +1309,7 @@ int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks, } } spin_unlock_irq(&bitmap->lock); + bitmap->allclean = 0; return rv; } @@ -1332,6 +1346,7 @@ void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int ab } unlock: spin_unlock_irqrestore(&bitmap->lock, flags); + bitmap->allclean = 0; } void bitmap_close_sync(struct bitmap *bitmap) @@ -1399,7 +1414,7 @@ static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int n set_page_attr(bitmap, page, BITMAP_PAGE_CLEAN); } spin_unlock_irq(&bitmap->lock); - + bitmap->allclean = 0; } /* dirty the memory and file bits for bitmap chunks "s" to "e" */ diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h index e51b531cd0b2..47fbcba11850 100644 --- a/include/linux/raid/bitmap.h +++ b/include/linux/raid/bitmap.h @@ -235,6 +235,8 @@ struct bitmap { unsigned long flags; + int allclean; + unsigned long max_write_behind; /* write-behind mode */ atomic_t behind_writes; -- 2.20.1