Re: [PATCH] A tentative patch to bypass REQ_META in blk throttle
Hi Tejun, On Thu, Apr 26, 2018 at 12:01:18PM -0700, Tejun Heo wrote: > Hello, > > On Fri, Apr 20, 2018 at 06:06:01PM +0800, Benlong Zhang wrote: > > One problem with cgwb is how fs should treat metadata bios. > > For example in xfs, the log might be partially stuck in one > > group, leaving threads in other groups waiting for too long. > > Please refer to the linux-xfs discussion: > > "[PATCH V2] xfs: implement cgroup writeback support" > > > > One approach is to correctly tag bio->bi_css from within the > > filesystems (for xfs log should be blkcg_root), and the other > > is to skip them, but relies on REQ_META being set. > > > > It works with xfs on a cgwb porting implementation to 3.10.0. > > But really not sure about other filesystems... > > Yeah, Josef (cc'd) is working on a similar approach but in a more > generic way. Good to know and looking forward to the code. Thank you for your reply! Benlong > > Thanks. > > -- > tejun
[PATCH] A tentative patch to bypass REQ_META in blk throttle
One problem with cgwb is how fs should treat metadata bios. For example in xfs, the log might be partially stuck in one group, leaving threads in other groups waiting for too long. Please refer to the linux-xfs discussion: "[PATCH V2] xfs: implement cgroup writeback support" One approach is to correctly tag bio->bi_css from within the filesystems (for xfs log should be blkcg_root), and the other is to skip them, but relies on REQ_META being set. It works with xfs on a cgwb porting implementation to 3.10.0. But really not sure about other filesystems... --- block/blk-throttle.c | 4 1 file changed, 4 insertions(+) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index c5a1316..e2abf6e 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -2159,6 +2159,10 @@ bool blk_throtl_bio(struct request_queue *q, struct blkcg_gq *blkg, if (bio_flagged(bio, BIO_THROTTLED) || !tg->has_rules[rw]) goto out; + /* bypass REQ_META for fs global resource */ + if (bio->bi_opf & REQ_META) + goto out; + spin_lock_irq(q->queue_lock); throtl_update_latency_buckets(td); -- 1.8.3.1
