Message ID | 20191006024516.19996-5-ming.lei@redhat.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | blk-mq: improvement on handling IO during CPU hotplug | expand |
On 10/6/19 4:45 AM, Ming Lei wrote: > When all CPUs in one hctx are offline, we shouldn't run this hw queue > for completing request any more. > > So steal bios from the request, and resubmit them, and finally free > the request in blk_mq_hctx_notify_dead(). > > Cc: Bart Van Assche <bvanassche@acm.org> > Cc: Hannes Reinecke <hare@suse.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Keith Busch <keith.busch@intel.com> > Signed-off-by: Ming Lei <ming.lei@redhat.com> > --- > block/blk-mq.c | 48 +++++++++++++++++++++++++++++++++++++++++------- > 1 file changed, 41 insertions(+), 7 deletions(-) > > diff --git a/block/blk-mq.c b/block/blk-mq.c > index d991c122abf2..0b35fdbd1f17 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2280,10 +2280,30 @@ static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node) > return 0; > } > > +static void blk_mq_resubmit_io(struct request *rq) > +{ > + struct bio_list list; > + struct bio *bio; > + > + bio_list_init(&list); > + blk_steal_bios(&list, rq); > + > + while (true) { > + bio = bio_list_pop(&list); > + if (!bio) > + break; > + > + generic_make_request(bio); > + } > + > + blk_mq_cleanup_rq(rq); > + blk_mq_end_request(rq, 0); > +} > + Hmm. Not sure if this is a good idea. Shouldn't we call 'blk_mq_end_request()' before calling generic_make_request()? otherwise the cloned request might be completed before original one, which looks a bit dodgy to me; and might lead to quite a recursion if we have several dead cpus to content with ... Cheers, Hannes
On Mon, Oct 07, 2019 at 08:27:38AM +0200, Hannes Reinecke wrote: > On 10/6/19 4:45 AM, Ming Lei wrote: > > When all CPUs in one hctx are offline, we shouldn't run this hw queue > > for completing request any more. > > > > So steal bios from the request, and resubmit them, and finally free > > the request in blk_mq_hctx_notify_dead(). > > > > Cc: Bart Van Assche <bvanassche@acm.org> > > Cc: Hannes Reinecke <hare@suse.com> > > Cc: Christoph Hellwig <hch@lst.de> > > Cc: Thomas Gleixner <tglx@linutronix.de> > > Cc: Keith Busch <keith.busch@intel.com> > > Signed-off-by: Ming Lei <ming.lei@redhat.com> > > --- > > block/blk-mq.c | 48 +++++++++++++++++++++++++++++++++++++++++------- > > 1 file changed, 41 insertions(+), 7 deletions(-) > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > index d991c122abf2..0b35fdbd1f17 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -2280,10 +2280,30 @@ static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node) > > return 0; > > } > > > > +static void blk_mq_resubmit_io(struct request *rq) > > +{ > > + struct bio_list list; > > + struct bio *bio; > > + > > + bio_list_init(&list); > > + blk_steal_bios(&list, rq); > > + > > + while (true) { > > + bio = bio_list_pop(&list); > > + if (!bio) > > + break; > > + > > + generic_make_request(bio); > > + } > > + > > + blk_mq_cleanup_rq(rq); > > + blk_mq_end_request(rq, 0); > > +} > > + > Hmm. Not sure if this is a good idea. > Shouldn't we call 'blk_mq_end_request()' before calling > generic_make_request()? > otherwise the cloned request might be completed before original one, > which looks a bit dodgy to me; and might lead to quite a recursion if we > have several dead cpus to content with ... Good catch, we should have freed the old empty request before calling generic_make_request(), will fix it in V3. Thanks, Ming
diff --git a/block/blk-mq.c b/block/blk-mq.c index d991c122abf2..0b35fdbd1f17 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2280,10 +2280,30 @@ static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node) return 0; } +static void blk_mq_resubmit_io(struct request *rq) +{ + struct bio_list list; + struct bio *bio; + + bio_list_init(&list); + blk_steal_bios(&list, rq); + + while (true) { + bio = bio_list_pop(&list); + if (!bio) + break; + + generic_make_request(bio); + } + + blk_mq_cleanup_rq(rq); + blk_mq_end_request(rq, 0); +} + /* - * 'cpu' is going away. splice any existing rq_list entries from this - * software queue to the hw queue dispatch list, and ensure that it - * gets run. + * 'cpu' has gone away. If this hctx is dead, we can't dispatch request + * to the hctx any more, so steal bios from requests of this hctx, and + * re-submit them to the request queue, and free these requests finally. */ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) { @@ -2291,6 +2311,8 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) struct blk_mq_ctx *ctx; LIST_HEAD(tmp); enum hctx_type type; + bool hctx_dead; + struct request *rq; hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead); ctx = __blk_mq_get_ctx(hctx->queue, cpu); @@ -2298,6 +2320,9 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) clear_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state); + hctx_dead = cpumask_first_and(hctx->cpumask, cpu_online_mask) >= + nr_cpu_ids; + spin_lock(&ctx->lock); if (!list_empty(&ctx->rq_lists[type])) { list_splice_init(&ctx->rq_lists[type], &tmp); @@ -2308,11 +2333,20 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) if (list_empty(&tmp)) return 0; - spin_lock(&hctx->lock); - list_splice_tail_init(&tmp, &hctx->dispatch); - spin_unlock(&hctx->lock); + if (!hctx_dead) { + spin_lock(&hctx->lock); + list_splice_tail_init(&tmp, &hctx->dispatch); + spin_unlock(&hctx->lock); + blk_mq_run_hw_queue(hctx, true); + return 0; + } + + while (!list_empty(&tmp)) { + rq = list_entry(tmp.next, struct request, queuelist); + list_del_init(&rq->queuelist); + blk_mq_resubmit_io(rq); + } - blk_mq_run_hw_queue(hctx, true); return 0; }
When all CPUs in one hctx are offline, we shouldn't run this hw queue for completing request any more. So steal bios from the request, and resubmit them, and finally free the request in blk_mq_hctx_notify_dead(). Cc: Bart Van Assche <bvanassche@acm.org> Cc: Hannes Reinecke <hare@suse.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Keith Busch <keith.busch@intel.com> Signed-off-by: Ming Lei <ming.lei@redhat.com> --- block/blk-mq.c | 48 +++++++++++++++++++++++++++++++++++++++++------- 1 file changed, 41 insertions(+), 7 deletions(-)