| Message ID | 1488975415-40417-1-git-send-email-houtao1@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed 08-03-17 20:16:55, Hou Tao wrote: > When adding a cfq_group into the cfq service tree, we use CFQ_IDLE_DELAY > as the delay of cfq_group's vdisktime if there have been other cfq_groups > already. > > When cfq is under iops mode, commit 9a7f38c42c2b ("cfq-iosched: Convert > from jiffies to nanoseconds") could result in a large iops delay and > lead to an abnormal io schedule delay for the added cfq_group. To fix > it, we just need to revert to the old CFQ_IDLE_DELAY value: HZ / 5 > when iops mode is enabled. > > Despite having the same value, the delay of a cfq_queue in idle class > and the delay of cfq_queue are different things, so I define two new > macros for the delay of a cfq_group under time-slice mode and IOPs mode. > > Fixes: 9a7f38c42c2b92391d9dabaf9f51df7cfe5608e4 > Cc: <stable@vger.kernel.org> # 4.8+ > Signed-off-by: Hou Tao <houtao1@huawei.com> OK, the number 200 is somewhat arbitrary but so is HZ/5 so I guess we are OK. You can add: Acked-by: Jan Kara <jack@suse.cz> Honza > --- > block/cfq-iosched.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > v2: > - use constant instead of "nsecs_to_jiffies64(CFQ_IDLE_DELAY)" > as suggested by Jan Kara > > v1: > https://www.spinics.net/lists/stable/msg160580.html > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index 440b95e..69754e8 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -38,9 +38,13 @@ static const u64 cfq_target_latency = (u64)NSEC_PER_SEC * 3/10; /* 300 ms */ > static const int cfq_hist_divisor = 4; > > /* > - * offset from end of service tree > + * offset from end of queue service tree for idle class > */ > #define CFQ_IDLE_DELAY (NSEC_PER_SEC / 5) > +/* offset from end of group service tree under time slice mode */ > +#define CFQ_SLICE_MODE_GROUP_DELAY (NSEC_PER_SEC / 5) > +/* offset from end of group service under IOPS mode */ > +#define CFQ_IOPS_MODE_GROUP_DELAY (200) > > /* > * below this threshold, we consider thinktime immediate > @@ -1362,6 +1366,14 @@ cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) > cfqg->vfraction = max_t(unsigned, vfr, 1); > } > > +static inline u64 cfq_get_cfqg_vdisktime_delay(struct cfq_data *cfqd) > +{ > + if (!iops_mode(cfqd)) > + return CFQ_SLICE_MODE_GROUP_DELAY; > + else > + return CFQ_IOPS_MODE_GROUP_DELAY; > +} > + > static void > cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg) > { > @@ -1381,7 +1393,8 @@ cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg) > n = rb_last(&st->rb); > if (n) { > __cfqg = rb_entry_cfqg(n); > - cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY; > + cfqg->vdisktime = __cfqg->vdisktime + > + cfq_get_cfqg_vdisktime_delay(cfqd); > } else > cfqg->vdisktime = st->min_vdisktime; > cfq_group_service_tree_add(st, cfqg); > -- > 2.5.0 >
On 03/08/2017 05:16 AM, Hou Tao wrote: > When adding a cfq_group into the cfq service tree, we use CFQ_IDLE_DELAY > as the delay of cfq_group's vdisktime if there have been other cfq_groups > already. > > When cfq is under iops mode, commit 9a7f38c42c2b ("cfq-iosched: Convert > from jiffies to nanoseconds") could result in a large iops delay and > lead to an abnormal io schedule delay for the added cfq_group. To fix > it, we just need to revert to the old CFQ_IDLE_DELAY value: HZ / 5 > when iops mode is enabled. > > Despite having the same value, the delay of a cfq_queue in idle class > and the delay of cfq_queue are different things, so I define two new > macros for the delay of a cfq_group under time-slice mode and IOPs mode. Added, thanks.
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 440b95e..69754e8 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -38,9 +38,13 @@ static const u64 cfq_target_latency = (u64)NSEC_PER_SEC * 3/10; /* 300 ms */ static const int cfq_hist_divisor = 4; /* - * offset from end of service tree + * offset from end of queue service tree for idle class */ #define CFQ_IDLE_DELAY (NSEC_PER_SEC / 5) +/* offset from end of group service tree under time slice mode */ +#define CFQ_SLICE_MODE_GROUP_DELAY (NSEC_PER_SEC / 5) +/* offset from end of group service under IOPS mode */ +#define CFQ_IOPS_MODE_GROUP_DELAY (200) /* * below this threshold, we consider thinktime immediate @@ -1362,6 +1366,14 @@ cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg) cfqg->vfraction = max_t(unsigned, vfr, 1); } +static inline u64 cfq_get_cfqg_vdisktime_delay(struct cfq_data *cfqd) +{ + if (!iops_mode(cfqd)) + return CFQ_SLICE_MODE_GROUP_DELAY; + else + return CFQ_IOPS_MODE_GROUP_DELAY; +} + static void cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg) { @@ -1381,7 +1393,8 @@ cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg) n = rb_last(&st->rb); if (n) { __cfqg = rb_entry_cfqg(n); - cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY; + cfqg->vdisktime = __cfqg->vdisktime + + cfq_get_cfqg_vdisktime_delay(cfqd); } else cfqg->vdisktime = st->min_vdisktime; cfq_group_service_tree_add(st, cfqg);
When adding a cfq_group into the cfq service tree, we use CFQ_IDLE_DELAY as the delay of cfq_group's vdisktime if there have been other cfq_groups already. When cfq is under iops mode, commit 9a7f38c42c2b ("cfq-iosched: Convert from jiffies to nanoseconds") could result in a large iops delay and lead to an abnormal io schedule delay for the added cfq_group. To fix it, we just need to revert to the old CFQ_IDLE_DELAY value: HZ / 5 when iops mode is enabled. Despite having the same value, the delay of a cfq_queue in idle class and the delay of cfq_queue are different things, so I define two new macros for the delay of a cfq_group under time-slice mode and IOPs mode. Fixes: 9a7f38c42c2b92391d9dabaf9f51df7cfe5608e4 Cc: <stable@vger.kernel.org> # 4.8+ Signed-off-by: Hou Tao <houtao1@huawei.com> --- block/cfq-iosched.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) v2: - use constant instead of "nsecs_to_jiffies64(CFQ_IDLE_DELAY)" as suggested by Jan Kara v1: https://www.spinics.net/lists/stable/msg160580.html