Messages in this thread | | | Date | Fri, 5 May 2023 21:35:21 +0800 | Subject | Re: [External] Re: [PATCH v2] blk-throttle: Fix io statistics for cgroup v1 | From | hanjinke <> |
| |
在 2023/5/5 上午5:13, Andrea Righi 写道: > On Thu, May 04, 2023 at 11:08:53PM +0800, hanjinke wrote: >> Hi >> >> Sorry for delay(Chinese Labor Day holiday). > > No problem, it was also Labor Day in Italy. :) > >> >> 在 2023/4/29 上午3:05, Andrea Righi 写道: >>> On Sat, Apr 01, 2023 at 05:47:08PM +0800, Jinke Han wrote: >>>> From: Jinke Han <hanjinke.666@bytedance.com> >>>> >>>> After commit f382fb0bcef4 ("block: remove legacy IO schedulers"), >>>> blkio.throttle.io_serviced and blkio.throttle.io_service_bytes become >>>> the only stable io stats interface of cgroup v1, and these statistics >>>> are done in the blk-throttle code. But the current code only counts the >>>> bios that are actually throttled. When the user does not add the throttle >>>> limit, the io stats for cgroup v1 has nothing. I fix it according to the >>>> statistical method of v2, and made it count all ios accurately. >>>> >>>> Fixes: a7b36ee6ba29 ("block: move blk-throtl fast path inline") >>>> Signed-off-by: Jinke Han <hanjinke.666@bytedance.com> >>> >>> Thanks for fixing this! >>> >>> The code looks correct to me, but this seems to report io statistics >>> only if at least one throttling limit is defined. IIRC with cgroup v1 it >>> was possible to see the io statistics inside a cgroup also with no >>> throttling limits configured. >>> >>> Basically to restore the old behavior we would need to drop the >>> cgroup_subsys_on_dfl() check, something like the following (on top of >>> your patch). >>> >>> But I'm not sure if we're breaking other behaviors in this way... >>> opinions? >>> >>> block/blk-cgroup.c | 3 --- >>> block/blk-throttle.h | 12 +++++------- >>> 2 files changed, 5 insertions(+), 10 deletions(-) >>> >>> diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c >>> index 79138bfc6001..43af86db7cf3 100644 >>> --- a/block/blk-cgroup.c >>> +++ b/block/blk-cgroup.c >>> @@ -2045,9 +2045,6 @@ void blk_cgroup_bio_start(struct bio *bio) >>> struct blkg_iostat_set *bis; >>> unsigned long flags; >>> - if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) >>> - return; >>> - >>> /* Root-level stats are sourced from system-wide IO stats */ >>> if (!cgroup_parent(blkcg->css.cgroup)) >>> return; >>> diff --git a/block/blk-throttle.h b/block/blk-throttle.h >>> index d1ccbfe9f797..bcb40ee2eeba 100644 >>> --- a/block/blk-throttle.h >>> +++ b/block/blk-throttle.h >>> @@ -185,14 +185,12 @@ static inline bool blk_should_throtl(struct bio *bio) >>> struct throtl_grp *tg = blkg_to_tg(bio->bi_blkg); >>> int rw = bio_data_dir(bio); >>> - if (!cgroup_subsys_on_dfl(io_cgrp_subsys)) { >>> - if (!bio_flagged(bio, BIO_CGROUP_ACCT)) { >>> - bio_set_flag(bio, BIO_CGROUP_ACCT); >>> - blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf, >>> - bio->bi_iter.bi_size); >>> - } >>> - blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1); >>> + if (!bio_flagged(bio, BIO_CGROUP_ACCT)) { >>> + bio_set_flag(bio, BIO_CGROUP_ACCT); >>> + blkg_rwstat_add(&tg->stat_bytes, bio->bi_opf, >>> + bio->bi_iter.bi_size); >>> } >>> + blkg_rwstat_add(&tg->stat_ios, bio->bi_opf, 1); >>
I checked the code again. If we remove cgroup_subsys_on_dfl check here, io statistics will still be performed in the case of v2, which I think is unnecessary, and this information will be counted to io_service_bytes/io_serviced, these two files are not visible in v2. Am I missing something?
Thanks. Jinke
| |