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authorNeilBrown <neilb@suse.de>2008-03-04 14:29:30 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-03-04 16:35:17 -0800
commit8311c29d40235062a843f4a8e8a70a44af6fe4c9 (patch)
treec869143fae8f135646300d1bac6639af5bb30dd7
parenta35e63efa1fb18c6f20f38e3ddf3f8ffbcf0f6e7 (diff)
downloadkernel-8311c29d40235062a843f4a8e8a70a44af6fe4c9.tar.gz
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 <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/md/bitmap.c19
-rw-r--r--include/linux/raid/bitmap.h2
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;