Messages in this thread | | | Subject | Re: [PATCH] blk-throttle: fix io hung due to config updates | From | Yu Kuai <> | Date | Fri, 1 Jul 2022 15:39:35 +0800 |
| |
On 2022/07/01 15:49, Yu Kuai wrote:
Please ignore this patch, it's been sent by mistake.
Kuai
> If new configuration is submitted while a bio is throttled, then new > waiting time is recalculated regardless that the bio might aready wait > for some time: > > tg_conf_updated > throtl_start_new_slice > tg_update_disptime > throtl_schedule_next_dispatch > > Then io hung can be triggered by always submmiting new configuration > before the throttled bio is dispatched. > > Fix the problem by respecting the time that throttled bio aready waited. > In order to do that, add new fields to record how many bytes/io already > waited, and use it to calculate wait time for throttled bio under new > configuration. > > Some simple test: > 1) > cd /sys/fs/cgroup/blkio/ > echo $$ > cgroup.procs > echo "8:0 2048" > blkio.throttle.write_bps_device > { > sleep 2 > echo "8:0 1024" > blkio.throttle.write_bps_device > } & > dd if=/dev/zero of=/dev/sda bs=8k count=1 oflag=direct > > 2) > cd /sys/fs/cgroup/blkio/ > echo $$ > cgroup.procs > echo "8:0 1024" > blkio.throttle.write_bps_device > { > sleep 4 > echo "8:0 2048" > blkio.throttle.write_bps_device > } & > dd if=/dev/zero of=/dev/sda bs=8k count=1 oflag=direct > > test results: io finish time > before this patch with this patch > 1) 10s 6s > 2) 8s 6s > > Signed-off-by: Yu Kuai <yukuai3@huawei.com> > --- > block/blk-throttle.c | 51 ++++++++++++++++++++++++++++++++++++++------ > block/blk-throttle.h | 9 ++++++++ > 2 files changed, 54 insertions(+), 6 deletions(-) > > diff --git a/block/blk-throttle.c b/block/blk-throttle.c > index 8612a071305e..8178ef278e7a 100644 > --- a/block/blk-throttle.c > +++ b/block/blk-throttle.c > @@ -639,6 +639,8 @@ static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg, > { > tg->bytes_disp[rw] = 0; > tg->io_disp[rw] = 0; > + tg->bytes_skipped[rw] = 0; > + tg->io_skipped[rw] = 0; > > /* > * Previous slice has expired. We must have trimmed it after last > @@ -656,12 +658,17 @@ static inline void throtl_start_new_slice_with_credit(struct throtl_grp *tg, > tg->slice_end[rw], jiffies); > } > > -static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw) > +static inline void throtl_start_new_slice(struct throtl_grp *tg, bool rw, > + bool clear_skipped) > { > tg->bytes_disp[rw] = 0; > tg->io_disp[rw] = 0; > tg->slice_start[rw] = jiffies; > tg->slice_end[rw] = jiffies + tg->td->throtl_slice; > + if (clear_skipped) { > + tg->bytes_skipped[rw] = 0; > + tg->io_skipped[rw] = 0; > + } > > throtl_log(&tg->service_queue, > "[%c] new slice start=%lu end=%lu jiffies=%lu", > @@ -783,6 +790,34 @@ static u64 calculate_bytes_allowed(u64 bps_limit, unsigned long jiffy_elapsed) > return mul_u64_u64_div_u64(bps_limit, (u64)jiffy_elapsed, (u64)HZ); > } > > +static void __tg_update_skipped(struct throtl_grp *tg, bool rw) > +{ > + unsigned long jiffy_elapsed = jiffies - tg->slice_start[rw]; > + u64 bps_limit = tg_bps_limit(tg, rw); > + u32 iops_limit = tg_iops_limit(tg, rw); > + > + if (bps_limit != U64_MAX) > + tg->bytes_skipped[rw] += > + calculate_bytes_allowed(bps_limit, jiffy_elapsed) - > + tg->bytes_disp[rw]; > + if (iops_limit != UINT_MAX) > + tg->io_skipped[rw] += > + calculate_io_allowed(iops_limit, jiffy_elapsed) - > + tg->io_disp[rw]; > +} > + > +static void tg_update_skipped(struct throtl_grp *tg) > +{ > + if (tg->service_queue.nr_queued[READ]) > + __tg_update_skipped(tg, READ); > + if (tg->service_queue.nr_queued[WRITE]) > + __tg_update_skipped(tg, WRITE); > + > + throtl_log(&tg->service_queue, "%s: %llu %llu %u %u\n", __func__, > + tg->bytes_skipped[READ], tg->bytes_skipped[WRITE], > + tg->io_skipped[READ], tg->io_skipped[WRITE]); > +} > + > static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio, > u32 iops_limit, unsigned long *wait) > { > @@ -800,7 +835,8 @@ static bool tg_with_in_iops_limit(struct throtl_grp *tg, struct bio *bio, > > /* Round up to the next throttle slice, wait time must be nonzero */ > jiffy_elapsed_rnd = roundup(jiffy_elapsed + 1, tg->td->throtl_slice); > - io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd); > + io_allowed = calculate_io_allowed(iops_limit, jiffy_elapsed_rnd) + > + tg->io_skipped[rw]; > if (tg->io_disp[rw] + 1 <= io_allowed) { > if (wait) > *wait = 0; > @@ -837,7 +873,8 @@ static bool tg_with_in_bps_limit(struct throtl_grp *tg, struct bio *bio, > jiffy_elapsed_rnd = tg->td->throtl_slice; > > jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, tg->td->throtl_slice); > - bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd); > + bytes_allowed = calculate_bytes_allowed(bps_limit, jiffy_elapsed_rnd) + > + tg->bytes_skipped[rw]; > if (tg->bytes_disp[rw] + bio_size <= bytes_allowed) { > if (wait) > *wait = 0; > @@ -898,7 +935,7 @@ static bool tg_may_dispatch(struct throtl_grp *tg, struct bio *bio, > * slice and it should be extended instead. > */ > if (throtl_slice_used(tg, rw) && !(tg->service_queue.nr_queued[rw])) > - throtl_start_new_slice(tg, rw); > + throtl_start_new_slice(tg, rw, true); > else { > if (time_before(tg->slice_end[rw], > jiffies + tg->td->throtl_slice)) > @@ -1327,8 +1364,8 @@ static void tg_conf_updated(struct throtl_grp *tg, bool global) > * that a group's limit are dropped suddenly and we don't want to > * account recently dispatched IO with new low rate. > */ > - throtl_start_new_slice(tg, READ); > - throtl_start_new_slice(tg, WRITE); > + throtl_start_new_slice(tg, READ, false); > + throtl_start_new_slice(tg, WRITE, false); > > if (tg->flags & THROTL_TG_PENDING) { > tg_update_disptime(tg); > @@ -1356,6 +1393,7 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of, > v = U64_MAX; > > tg = blkg_to_tg(ctx.blkg); > + tg_update_skipped(tg); > > if (is_u64) > *(u64 *)((void *)tg + of_cft(of)->private) = v; > @@ -1542,6 +1580,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of, > return ret; > > tg = blkg_to_tg(ctx.blkg); > + tg_update_skipped(tg); > > v[0] = tg->bps_conf[READ][index]; > v[1] = tg->bps_conf[WRITE][index]; > diff --git a/block/blk-throttle.h b/block/blk-throttle.h > index c1b602996127..371d624af845 100644 > --- a/block/blk-throttle.h > +++ b/block/blk-throttle.h > @@ -115,6 +115,15 @@ struct throtl_grp { > uint64_t bytes_disp[2]; > /* Number of bio's dispatched in current slice */ > unsigned int io_disp[2]; > + /* > + * The following two fields are used to calculate new wait time for > + * throttled bio when new configuration is submmited. > + * > + * Number of bytes will be skipped in current slice > + */ > + uint64_t bytes_skipped[2]; > + /* Number of bio will be skipped in current slice */ > + unsigned int io_skipped[2]; > > unsigned long last_low_overflow_time[2]; >
| |