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blk-throttle: respect 0 bps/iops settings for io.low

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If a cgroup with low limit 0 for both bps/iops, the cgroup's low limit
is ignored and we throttle the cgroup with its max limit. In this way,
other cgroups with a low limit will not get protected. To fix this, we
don't do the exception any more. cgroup will be throttled to a limit 0
if it uese default setting. To avoid completed stall, we give such
cgroup tiny IO resources.

Signed-off-by: Shaohua Li <shli@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Shaohua Li 2017-05-17 13:07:26 -07:00 committed by Jens Axboe
parent 4cff729f62
commit 9bb67aeb96
1 changed files with 29 additions and 12 deletions
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41
block/blk-throttle.c
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@ -27,6 +27,8 @@ static int throtl_quantum = 32;
#define MAX_IDLE_TIME (5L * 1000 * 1000) /* 5 s */
/* default latency target is 0, eg, guarantee IO latency by default */
#define DFL_LATENCY_TARGET (0)
#define MIN_THROTL_BPS (320 * 1024)
#define MIN_THROTL_IOPS (10)
#define SKIP_LATENCY (((u64)1) << BLK_STAT_RES_SHIFT)
@ -296,8 +298,14 @@ static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw)
td = tg->td;
ret = tg->bps[rw][td->limit_index];
if (ret == 0 && td->limit_index == LIMIT_LOW)
return tg->bps[rw][LIMIT_MAX];
if (ret == 0 && td->limit_index == LIMIT_LOW) {
/* intermediate node or iops isn't 0 */
if (!list_empty(&blkg->blkcg->css.children) ||
tg->iops[rw][td->limit_index])
return U64_MAX;
else
return MIN_THROTL_BPS;
}
if (td->limit_index == LIMIT_MAX && tg->bps[rw][LIMIT_LOW] &&
tg->bps[rw][LIMIT_LOW] != tg->bps[rw][LIMIT_MAX]) {
@ -317,10 +325,17 @@ static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent)
return UINT_MAX;
td = tg->td;
ret = tg->iops[rw][td->limit_index];
if (ret == 0 && tg->td->limit_index == LIMIT_LOW)
return tg->iops[rw][LIMIT_MAX];
if (ret == 0 && tg->td->limit_index == LIMIT_LOW) {
/* intermediate node or bps isn't 0 */
if (!list_empty(&blkg->blkcg->css.children) ||
tg->bps[rw][td->limit_index])
return UINT_MAX;
else
return MIN_THROTL_IOPS;
}
if (td->limit_index == LIMIT_MAX && tg->iops[rw][LIMIT_LOW] &&
tg->iops[rw][LIMIT_LOW] != tg->iops[rw][LIMIT_MAX]) {
@ -1353,7 +1368,7 @@ static int tg_print_conf_uint(struct seq_file *sf, void *v)
return 0;
}
static void tg_conf_updated(struct throtl_grp *tg)
static void tg_conf_updated(struct throtl_grp *tg, bool global)
{
struct throtl_service_queue *sq = &tg->service_queue;
struct cgroup_subsys_state *pos_css;
@ -1371,7 +1386,8 @@ static void tg_conf_updated(struct throtl_grp *tg)
* restrictions in the whole hierarchy and allows them to bypass
* blk-throttle.
*/
blkg_for_each_descendant_pre(blkg, pos_css, tg_to_blkg(tg)) {
blkg_for_each_descendant_pre(blkg, pos_css,
global ? tg->td->queue->root_blkg : tg_to_blkg(tg)) {
struct throtl_grp *this_tg = blkg_to_tg(blkg);
struct throtl_grp *parent_tg;
@ -1434,7 +1450,7 @@ static ssize_t tg_set_conf(struct kernfs_open_file *of,
else
*(unsigned int *)((void *)tg + of_cft(of)->private) = v;
tg_conf_updated(tg);
tg_conf_updated(tg, false);
ret = 0;
out_finish:
blkg_conf_finish(&ctx);
@ -1522,16 +1538,16 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
tg->latency_target_conf == DFL_LATENCY_TARGET)))
return 0;
if (tg->bps_conf[READ][off] != bps_dft)
if (tg->bps_conf[READ][off] != U64_MAX)
snprintf(bufs[0], sizeof(bufs[0]), "%llu",
tg->bps_conf[READ][off]);
if (tg->bps_conf[WRITE][off] != bps_dft)
if (tg->bps_conf[WRITE][off] != U64_MAX)
snprintf(bufs[1], sizeof(bufs[1]), "%llu",
tg->bps_conf[WRITE][off]);
if (tg->iops_conf[READ][off] != iops_dft)
if (tg->iops_conf[READ][off] != UINT_MAX)
snprintf(bufs[2], sizeof(bufs[2]), "%u",
tg->iops_conf[READ][off]);
if (tg->iops_conf[WRITE][off] != iops_dft)
if (tg->iops_conf[WRITE][off] != UINT_MAX)
snprintf(bufs[3], sizeof(bufs[3]), "%u",
tg->iops_conf[WRITE][off]);
if (off == LIMIT_LOW) {
@ -1654,7 +1670,8 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of,
tg->latency_target_conf = latency_time;
tg->latency_target = tg->latency_target_conf;
}
tg_conf_updated(tg);
tg_conf_updated(tg, index == LIMIT_LOW &&
tg->td->limit_valid[LIMIT_LOW]);
ret = 0;
out_finish:
blkg_conf_finish(&ctx);