| Message ID | 20221123060401.20392-2-shikemeng@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | A few bugfix and cleanup patches for blk-throttle | expand |
On Wed, Nov 23, 2022 at 02:03:51PM +0800, Kemeng Shi wrote: > Quoted from comment in throtl_pd_init: "If on the default hierarchy, we > switch to properly hierarchical behavior where limits on a given > throtl_grp are applied to the whole subtree rather than just the group > itself. e.g. If 16M read_bps limit is set on the root group, the whole > system can' exceed 16M for the device." On the default hierarchy (cgroup2), the throttle interface files don't exist in the root cgroup. In general, cgroup doesn't wanna be in the business of restricting resources at the system level. Thanks.
on 11/24/2022 1:11 AM, Tejun Heo wrote: > On Wed, Nov 23, 2022 at 02:03:51PM +0800, Kemeng Shi wrote: >> Quoted from comment in throtl_pd_init: "If on the default hierarchy, we >> switch to properly hierarchical behavior where limits on a given >> throtl_grp are applied to the whole subtree rather than just the group >> itself. e.g. If 16M read_bps limit is set on the root group, the whole >> system can' exceed 16M for the device." > > On the default hierarchy (cgroup2), the throttle interface files don't exist > in the root cgroup. In general, cgroup doesn't wanna be in the business of > restricting resources at the system level. Hi, Tejun. Thanks for review. If restricting is not needed anymore, the stale comment "e.g. If 16M read_bps limit is set on the root group, the whole system can' exceed 16M for the device." may better be remove. I will remove this in next version.
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 847721dc2b2b..96aa53e30e28 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -150,9 +150,6 @@ static uint64_t tg_bps_limit(struct throtl_grp *tg, int rw) struct throtl_data *td; uint64_t ret; - if (cgroup_subsys_on_dfl(io_cgrp_subsys) && !blkg->parent) - return U64_MAX; - td = tg->td; ret = tg->bps[rw][td->limit_index]; if (ret == 0 && td->limit_index == LIMIT_LOW) { @@ -180,9 +177,6 @@ static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw) struct throtl_data *td; unsigned int ret; - 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) {
Quoted from comment in throtl_pd_init: "If on the default hierarchy, we switch to properly hierarchical behavior where limits on a given throtl_grp are applied to the whole subtree rather than just the group itself. e.g. If 16M read_bps limit is set on the root group, the whole system can' exceed 16M for the device." Commit b22c417c885ea9 ("blk-throttle: configure bps/iops limit for cgroup in low limit") broke this rule and did not explain why. Restore the ability to limit the whole system by root group. Signed-off-by: Kemeng Shi <shikemeng@huawei.com> --- block/blk-throttle.c | 6 ------ 1 file changed, 6 deletions(-)