From cce990efc8f2a58c8d0fa11c234ddf2242b1b856 Mon Sep 17 00:00:00 2001 From: Sage Weil Date: Tue, 1 Oct 2013 09:28:29 -0700 Subject: [PATCH] osdc/ObjectCacher: limit writeback IOs generated while holding lock While analyzing a log from Mike Dawson I saw a long stall while librbd's objectcacher was starting lots (many hundreds) of IOs. Limit the amount of time we spend doing this at a time to allow IO replies to be processed so that the cache remains responsive. I'm not sure this warrants a tunable (which we would need to add for both libcephfs and librbd). Signed-off-by: Sage Weil --- src/osdc/ObjectCacher.cc | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/osdc/ObjectCacher.cc b/src/osdc/ObjectCacher.cc index 590b5d473a8d..81335b7957f3 100644 --- a/src/osdc/ObjectCacher.cc +++ b/src/osdc/ObjectCacher.cc @@ -11,6 +11,8 @@ #include "include/assert.h" +#define MAX_FLUSH_UNDER_LOCK 20 ///< max bh's we start writeback on while holding the lock + /*** ObjectCacher::BufferHead ***/ @@ -1448,8 +1450,10 @@ void ObjectCacher::flusher_entry() utime_t cutoff = ceph_clock_now(cct); cutoff -= max_dirty_age; BufferHead *bh = 0; + int max = MAX_FLUSH_UNDER_LOCK; while ((bh = static_cast(bh_lru_dirty.lru_get_next_expire())) != 0 && - bh->last_write < cutoff) { + bh->last_write < cutoff && + --max > 0) { ldout(cct, 10) << "flusher flushing aged dirty bh " << *bh << dendl; bh_write(bh); } -- 2.47.3