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blk-iocost: use local[64]_t for percpu stat

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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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tejun Heo 2020-09-01 14:52:33 -04:00 committed by Jens Axboe
parent 1f06959bd2
commit 5e124f7432
1 changed files with 27 additions and 10 deletions
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37
block/blk-iocost.c
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@ -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);
this_cpu_add(ioc->pcpu_stat->rq_wait_ns, rq_wait_ns);
local64_add(rq_wait_ns, &ccs->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;