From: Tejun Heo <tj@kernel.org>
To: axboe@kernel.dk
Cc: linux-block@vger.kernel.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@fb.com, newella@fb.com,
Tejun Heo <tj@kernel.org>
Subject: [PATCH 03/27] blk-iocost: use local[64]_t for percpu stat
Date: Tue, 1 Sep 2020 14:52:33 -0400 [thread overview]
Message-ID: <20200901185257.645114-4-tj@kernel.org> (raw)
In-Reply-To: <20200901185257.645114-1-tj@kernel.org>
blk-iocost has been reading percpu stat counters from remote cpus which on
some archs can lead to torn reads in really rare occassions. Use local[64]_t
for those counters.
Signed-off-by: Tejun Heo <tj@kernel.org>
---
block/blk-iocost.c | 37 +++++++++++++++++++++++++++----------
1 file changed, 27 insertions(+), 10 deletions(-)
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index d37b55db2409..e2266e7692b4 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -179,6 +179,8 @@
#include <linux/parser.h>
#include <linux/sched/signal.h>
#include <linux/blk-cgroup.h>
+#include <asm/local.h>
+#include <asm/local64.h>
#include "blk-rq-qos.h"
#include "blk-stat.h"
#include "blk-wbt.h"
@@ -373,8 +375,8 @@ struct ioc_params {
};
struct ioc_missed {
- u32 nr_met;
- u32 nr_missed;
+ local_t nr_met;
+ local_t nr_missed;
u32 last_met;
u32 last_missed;
};
@@ -382,7 +384,7 @@ struct ioc_missed {
struct ioc_pcpu_stat {
struct ioc_missed missed[2];
- u64 rq_wait_ns;
+ local64_t rq_wait_ns;
u64 last_rq_wait_ns;
};
@@ -1278,8 +1280,8 @@ static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p
u64 this_rq_wait_ns;
for (rw = READ; rw <= WRITE; rw++) {
- u32 this_met = READ_ONCE(stat->missed[rw].nr_met);
- u32 this_missed = READ_ONCE(stat->missed[rw].nr_missed);
+ u32 this_met = local_read(&stat->missed[rw].nr_met);
+ u32 this_missed = local_read(&stat->missed[rw].nr_missed);
nr_met[rw] += this_met - stat->missed[rw].last_met;
nr_missed[rw] += this_missed - stat->missed[rw].last_missed;
@@ -1287,7 +1289,7 @@ static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p
stat->missed[rw].last_missed = this_missed;
}
- this_rq_wait_ns = READ_ONCE(stat->rq_wait_ns);
+ this_rq_wait_ns = local64_read(&stat->rq_wait_ns);
rq_wait_ns += this_rq_wait_ns - stat->last_rq_wait_ns;
stat->last_rq_wait_ns = this_rq_wait_ns;
}
@@ -1908,6 +1910,7 @@ static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)
static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
{
struct ioc *ioc = rqos_to_ioc(rqos);
+ struct ioc_pcpu_stat *ccs;
u64 on_q_ns, rq_wait_ns, size_nsec;
int pidx, rw;
@@ -1931,13 +1934,17 @@ static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns;
size_nsec = div64_u64(calc_size_vtime_cost(rq, ioc), VTIME_PER_NSEC);
+ ccs = get_cpu_ptr(ioc->pcpu_stat);
+
if (on_q_ns <= size_nsec ||
on_q_ns - size_nsec <= ioc->params.qos[pidx] * NSEC_PER_USEC)
- this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_met);
+ local_inc(&ccs->missed[rw].nr_met);
else
- this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_missed);
+ local_inc(&ccs->missed[rw].nr_missed);
+
+ local64_add(rq_wait_ns, &ccs->rq_wait_ns);
- this_cpu_add(ioc->pcpu_stat->rq_wait_ns, rq_wait_ns);
+ put_cpu_ptr(ccs);
}
static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos)
@@ -1977,7 +1984,7 @@ static int blk_iocost_init(struct request_queue *q)
{
struct ioc *ioc;
struct rq_qos *rqos;
- int ret;
+ int i, cpu, ret;
ioc = kzalloc(sizeof(*ioc), GFP_KERNEL);
if (!ioc)
@@ -1989,6 +1996,16 @@ static int blk_iocost_init(struct request_queue *q)
return -ENOMEM;
}
+ for_each_possible_cpu(cpu) {
+ struct ioc_pcpu_stat *ccs = per_cpu_ptr(ioc->pcpu_stat, cpu);
+
+ for (i = 0; i < ARRAY_SIZE(ccs->missed); i++) {
+ local_set(&ccs->missed[i].nr_met, 0);
+ local_set(&ccs->missed[i].nr_missed, 0);
+ }
+ local64_set(&ccs->rq_wait_ns, 0);
+ }
+
rqos = &ioc->rqos;
rqos->id = RQ_QOS_COST;
rqos->ops = &ioc_rqos_ops;
--
2.26.2
next prev parent reply other threads:[~2020-09-01 18:53 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 18:52 [PATCHSET for-5.10/block] blk-iocost: iocost: improve donation, debt and excess handling Tejun Heo
2020-09-01 18:52 ` [PATCH 01/27] blk-iocost: ioc_pd_free() shouldn't assume irq disabled Tejun Heo
2020-09-01 18:52 ` [PATCH 02/27] blk-stat: make q->stats->lock irqsafe Tejun Heo
2020-09-01 18:52 ` Tejun Heo [this message]
2020-11-20 21:51 ` [PATCH 03/27] blk-iocost: use local[64]_t for percpu stat Stafford Horne
2020-11-20 22:13 ` Tejun Heo
2020-09-01 18:52 ` [PATCH 04/27] blk-iocost: rename propagate_active_weights() to propagate_weights() Tejun Heo
2020-09-01 18:52 ` [PATCH 05/27] blk-iocost: clamp inuse and skip noops in __propagate_weights() Tejun Heo
2020-09-01 18:52 ` [PATCH 06/27] blk-iocost: move iocg_kick_delay() above iocg_kick_waitq() Tejun Heo
2020-09-01 18:52 ` [PATCH 07/27] blk-iocost: make iocg_kick_waitq() call iocg_kick_delay() after paying debt Tejun Heo
2020-09-01 18:52 ` [PATCH 08/27] blk-iocost: s/HWEIGHT_WHOLE/WEIGHT_ONE/g Tejun Heo
2020-09-01 18:52 ` [PATCH 09/27] blk-iocost: use WEIGHT_ONE based fixed point number for weights Tejun Heo
2020-09-01 18:52 ` [PATCH 10/27] blk-iocost: make ioc_now->now and ioc->period_at 64bit Tejun Heo
2020-09-01 18:52 ` [PATCH 11/27] blk-iocost: streamline vtime margin and timer slack handling Tejun Heo
2020-09-01 18:52 ` [PATCH 12/27] blk-iocost: grab ioc->lock for debt handling Tejun Heo
2020-09-01 18:52 ` [PATCH 13/27] blk-iocost: add absolute usage stat Tejun Heo
2020-09-01 18:52 ` [PATCH 14/27] blk-iocost: calculate iocg->usages[] from iocg->local_stat.usage_us Tejun Heo
2020-09-01 18:52 ` [PATCH 15/27] blk-iocost: replace iocg->has_surplus with ->surplus_list Tejun Heo
2020-09-01 18:52 ` [PATCH 16/27] blk-iocost: decouple vrate adjustment from surplus transfers Tejun Heo
2020-09-01 18:52 ` [PATCH 17/27] blk-iocost: restructure surplus donation logic Tejun Heo
2020-09-01 18:52 ` [PATCH 18/27] blk-iocost: implement Andy's method for donation weight updates Tejun Heo
2020-09-01 18:52 ` [PATCH 19/27] blk-iocost: revamp donation amount determination Tejun Heo
2020-09-01 18:52 ` [PATCH 20/27] blk-iocost: revamp in-period donation snapbacks Tejun Heo
2020-09-01 18:52 ` [PATCH 21/27] blk-iocost: revamp debt handling Tejun Heo
2020-09-01 18:52 ` [PATCH 22/27] blk-iocost: implement delay adjustment hysteresis Tejun Heo
2020-09-01 18:52 ` [PATCH 23/27] blk-iocost: halve debts if device stays idle Tejun Heo
2020-09-01 18:52 ` [PATCH 24/27] blk-iocost: implement vtime loss compensation Tejun Heo
2020-09-01 18:52 ` [PATCH 25/27] blk-iocost: restore inuse update tracepoints Tejun Heo
2020-09-01 18:52 ` [PATCH 26/27] blk-iocost: add three debug stat - cost.wait, indebt and indelay Tejun Heo
2020-09-01 18:52 ` [PATCH 27/27] blk-iocost: update iocost_monitor.py Tejun Heo
2020-09-01 22:57 ` [PATCHSET for-5.10/block] blk-iocost: iocost: improve donation, debt and excess handling Jens Axboe
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