@@ -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 +790,41 @@ 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);
+
+ /*
+ * Following calculation won't overflow as long as bios that are
+ * dispatched later won't preempt already throttled bios. Even if such
+ * overflow do happen, there should be no problem because we are using
+ * unsigned here, and bytes_skipped/io_skipped will be updated
+ * correctly.
+ */
+ 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 +842,8 @@ 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 +880,8 @@ 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 +942,7 @@ 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 +1371,8 @@ 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 +1400,7 @@ 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 +1587,7 @@ 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];
@@ -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];
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> Reviewed-by: Michal Koutný <mkoutny@suse.com> --- block/blk-throttle.c | 58 +++++++++++++++++++++++++++++++++++++++----- block/blk-throttle.h | 9 +++++++ 2 files changed, 61 insertions(+), 6 deletions(-)