From: Sagi Grimberg <sagi@grimberg.me>
To: Jens Axboe <axboe@kernel.dk>,
linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
Keith Busch <kbusch@kernel.org>
Cc: linux-block@vger.kernel.org, Ming Lin <mlin@kernel.org>,
Chao Leng <lengchao@huawei.com>
Subject: Re: [PATCH v4 1/2] blk-mq: add async quiesce interface
Date: Mon, 27 Jul 2020 15:37:16 -0700 [thread overview]
Message-ID: <e22c2f2f-6924-0090-d841-da2d84c606ae@grimberg.me> (raw)
In-Reply-To: <fe247bae-8428-bca8-81b5-a7015bc39591@kernel.dk>
>> +void blk_mq_quiesce_queue_async(struct request_queue *q)
>> +{
>> + struct blk_mq_hw_ctx *hctx;
>> + unsigned int i;
>> + int rcu = false;
>> +
>> + blk_mq_quiesce_queue_nowait(q);
>> +
>> + queue_for_each_hw_ctx(q, hctx, i) {
>> + hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync), GFP_KERNEL);
>> + if (!hctx->rcu_sync) {
>> + /* fallback to serial rcu sync */
>> + if (hctx->flags & BLK_MQ_F_BLOCKING)
>> + synchronize_srcu(hctx->srcu);
>> + else
>> + rcu = true;
>> + } else {
>> + init_completion(&hctx->rcu_sync->completion);
>> + init_rcu_head(&hctx->rcu_sync->head);
>> + if (hctx->flags & BLK_MQ_F_BLOCKING)
>> + call_srcu(hctx->srcu, &hctx->rcu_sync->head,
>> + wakeme_after_rcu);
>> + else
>> + call_rcu(&hctx->rcu_sync->head,
>> + wakeme_after_rcu);
>> + }
>> + }
>> + if (rcu)
>> + synchronize_rcu();
>> +}
>> +EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_async);
>
> This won't always be async, and that might matter to some users. I think
> it'd be better to put the fallback path into the _wait() part instead,
> since the caller should expect that to be blocking/waiting as the name
> implies.
>
> Nit picking, but...
Makes sense..
I thought more about Keith suggestion for an interface that accepts a
tagset. It allows us to decide what we do based on the tagset itself
which is now passed in the interface.
What do you think about:
--
diff --git a/block/blk-mq.c b/block/blk-mq.c
index abcf590f6238..d4b24aa1a766 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -209,6 +209,43 @@ void blk_mq_quiesce_queue_nowait(struct
request_queue *q)
}
EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
+static void blk_mq_quiesce_queue_async(struct request_queue *q)
+{
+ struct blk_mq_hw_ctx *hctx;
+ unsigned int i;
+
+ blk_mq_quiesce_queue_nowait(q);
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (!(hctx->flags & BLK_MQ_F_BLOCKING))
+ continue;
+
+ hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync),
GFP_KERNEL);
+ if (!hctx->rcu_sync)
+ continue;
+
+ init_completion(&hctx->rcu_sync->completion);
+ init_rcu_head(&hctx->rcu_sync->head);
+ call_srcu(hctx->srcu, &hctx->rcu_sync->head,
+ wakeme_after_rcu);
+ }
+}
+
+static void blk_mq_quiesce_queue_async_wait(struct request_queue *q)
+{
+ struct blk_mq_hw_ctx *hctx;
+ unsigned int i;
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (!hctx->rcu_sync) {
+ synchronize_srcu(hctx->srcu);
+ continue;
+ }
+ wait_for_completion(&hctx->rcu_sync->completion);
+ destroy_rcu_head(&hctx->rcu_sync->head);
+ }
+}
+
/**
* blk_mq_quiesce_queue() - wait until all ongoing dispatches have
finished
* @q: request queue.
@@ -2884,6 +2921,39 @@ static void queue_set_hctx_shared(struct
request_queue *q, bool shared)
}
}
+void blk_mq_quiesce_tagset(struct blk_mq_tag_set *set)
+{
+ struct request_queue *q;
+
+ mutex_lock(&set->tag_list_lock);
+ list_for_each_entry(q, &set->tag_list, tag_set_list) {
+ if (!(set->flags & BLK_MQ_F_BLOCKING))
+ blk_mq_quiesce_queue_nowait(q);
+ else
+ blk_mq_quiesce_queue_async(q);
+ }
+
+ if (!(set->flags & BLK_MQ_F_BLOCKING)) {
+ synchronize_rcu();
+ } else {
+ list_for_each_entry(q, &set->tag_list, tag_set_list)
+ blk_mq_quiesce_queue_async_wait(q);
+ }
+ mutex_unlock(&set->tag_list_lock);
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_tagset);
+
+void blk_mq_unquiesce_tagset(struct blk_mq_tag_set *set)
+{
+ struct request_queue *q;
+
+ mutex_lock(&set->tag_list_lock);
+ list_for_each_entry(q, &set->tag_list, tag_set_list)
+ blk_mq_unquiesce_queue(q);
+ mutex_unlock(&set->tag_list_lock);
+}
+EXPORT_SYMBOL_GPL(blk_mq_unquiesce_tagset);
+
static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set,
bool shared)
{
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 23230c1d031e..a85f2dedc947 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -5,6 +5,7 @@
#include <linux/blkdev.h>
#include <linux/sbitmap.h>
#include <linux/srcu.h>
+#include <linux/rcupdate_wait.h>
struct blk_mq_tags;
struct blk_flush_queue;
@@ -170,6 +171,7 @@ struct blk_mq_hw_ctx {
*/
struct list_head hctx_list;
+ struct rcu_synchronize *rcu_sync;
/**
* @srcu: Sleepable RCU. Use as lock when type of the hardware
queue is
* blocking (BLK_MQ_F_BLOCKING). Must be the last member - see also
@@ -532,6 +534,8 @@ int blk_mq_map_queues(struct blk_mq_queue_map *qmap);
void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int
nr_hw_queues);
void blk_mq_quiesce_queue_nowait(struct request_queue *q);
+void blk_mq_quiesce_tagset(struct request_queue *q);
+void blk_mq_unquiesce_tagset(struct request_queue *q);
unsigned int blk_mq_rq_cpu(struct request *rq);
--
And then nvme will use it:
--
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 05aa568a60af..c41df20996d7 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4557,23 +4557,13 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
void nvme_stop_queues(struct nvme_ctrl *ctrl)
{
- struct nvme_ns *ns;
-
- down_read(&ctrl->namespaces_rwsem);
- list_for_each_entry(ns, &ctrl->namespaces, list)
- blk_mq_quiesce_queue(ns->queue);
- up_read(&ctrl->namespaces_rwsem);
+ blk_mq_quiesce_tagset(ctrl->tagset);
}
EXPORT_SYMBOL_GPL(nvme_stop_queues);
void nvme_start_queues(struct nvme_ctrl *ctrl)
{
- struct nvme_ns *ns;
-
- down_read(&ctrl->namespaces_rwsem);
- list_for_each_entry(ns, &ctrl->namespaces, list)
- blk_mq_unquiesce_queue(ns->queue);
- up_read(&ctrl->namespaces_rwsem);
+ blk_mq_unquiesce_tagset(ctrl->tagset);
}
EXPORT_SYMBOL_GPL(nvme_start_queues);
--
Thoughts?
WARNING: multiple messages have this Message-ID (diff)
From: Sagi Grimberg <sagi@grimberg.me>
To: Jens Axboe <axboe@kernel.dk>,
linux-nvme@lists.infradead.org, Christoph Hellwig <hch@lst.de>,
Keith Busch <kbusch@kernel.org>
Cc: linux-block@vger.kernel.org, Ming Lin <mlin@kernel.org>,
Chao Leng <lengchao@huawei.com>
Subject: Re: [PATCH v4 1/2] blk-mq: add async quiesce interface
Date: Mon, 27 Jul 2020 15:37:16 -0700 [thread overview]
Message-ID: <e22c2f2f-6924-0090-d841-da2d84c606ae@grimberg.me> (raw)
In-Reply-To: <fe247bae-8428-bca8-81b5-a7015bc39591@kernel.dk>
>> +void blk_mq_quiesce_queue_async(struct request_queue *q)
>> +{
>> + struct blk_mq_hw_ctx *hctx;
>> + unsigned int i;
>> + int rcu = false;
>> +
>> + blk_mq_quiesce_queue_nowait(q);
>> +
>> + queue_for_each_hw_ctx(q, hctx, i) {
>> + hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync), GFP_KERNEL);
>> + if (!hctx->rcu_sync) {
>> + /* fallback to serial rcu sync */
>> + if (hctx->flags & BLK_MQ_F_BLOCKING)
>> + synchronize_srcu(hctx->srcu);
>> + else
>> + rcu = true;
>> + } else {
>> + init_completion(&hctx->rcu_sync->completion);
>> + init_rcu_head(&hctx->rcu_sync->head);
>> + if (hctx->flags & BLK_MQ_F_BLOCKING)
>> + call_srcu(hctx->srcu, &hctx->rcu_sync->head,
>> + wakeme_after_rcu);
>> + else
>> + call_rcu(&hctx->rcu_sync->head,
>> + wakeme_after_rcu);
>> + }
>> + }
>> + if (rcu)
>> + synchronize_rcu();
>> +}
>> +EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_async);
>
> This won't always be async, and that might matter to some users. I think
> it'd be better to put the fallback path into the _wait() part instead,
> since the caller should expect that to be blocking/waiting as the name
> implies.
>
> Nit picking, but...
Makes sense..
I thought more about Keith suggestion for an interface that accepts a
tagset. It allows us to decide what we do based on the tagset itself
which is now passed in the interface.
What do you think about:
--
diff --git a/block/blk-mq.c b/block/blk-mq.c
index abcf590f6238..d4b24aa1a766 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -209,6 +209,43 @@ void blk_mq_quiesce_queue_nowait(struct
request_queue *q)
}
EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
+static void blk_mq_quiesce_queue_async(struct request_queue *q)
+{
+ struct blk_mq_hw_ctx *hctx;
+ unsigned int i;
+
+ blk_mq_quiesce_queue_nowait(q);
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (!(hctx->flags & BLK_MQ_F_BLOCKING))
+ continue;
+
+ hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync),
GFP_KERNEL);
+ if (!hctx->rcu_sync)
+ continue;
+
+ init_completion(&hctx->rcu_sync->completion);
+ init_rcu_head(&hctx->rcu_sync->head);
+ call_srcu(hctx->srcu, &hctx->rcu_sync->head,
+ wakeme_after_rcu);
+ }
+}
+
+static void blk_mq_quiesce_queue_async_wait(struct request_queue *q)
+{
+ struct blk_mq_hw_ctx *hctx;
+ unsigned int i;
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (!hctx->rcu_sync) {
+ synchronize_srcu(hctx->srcu);
+ continue;
+ }
+ wait_for_completion(&hctx->rcu_sync->completion);
+ destroy_rcu_head(&hctx->rcu_sync->head);
+ }
+}
+
/**
* blk_mq_quiesce_queue() - wait until all ongoing dispatches have
finished
* @q: request queue.
@@ -2884,6 +2921,39 @@ static void queue_set_hctx_shared(struct
request_queue *q, bool shared)
}
}
+void blk_mq_quiesce_tagset(struct blk_mq_tag_set *set)
+{
+ struct request_queue *q;
+
+ mutex_lock(&set->tag_list_lock);
+ list_for_each_entry(q, &set->tag_list, tag_set_list) {
+ if (!(set->flags & BLK_MQ_F_BLOCKING))
+ blk_mq_quiesce_queue_nowait(q);
+ else
+ blk_mq_quiesce_queue_async(q);
+ }
+
+ if (!(set->flags & BLK_MQ_F_BLOCKING)) {
+ synchronize_rcu();
+ } else {
+ list_for_each_entry(q, &set->tag_list, tag_set_list)
+ blk_mq_quiesce_queue_async_wait(q);
+ }
+ mutex_unlock(&set->tag_list_lock);
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_tagset);
+
+void blk_mq_unquiesce_tagset(struct blk_mq_tag_set *set)
+{
+ struct request_queue *q;
+
+ mutex_lock(&set->tag_list_lock);
+ list_for_each_entry(q, &set->tag_list, tag_set_list)
+ blk_mq_unquiesce_queue(q);
+ mutex_unlock(&set->tag_list_lock);
+}
+EXPORT_SYMBOL_GPL(blk_mq_unquiesce_tagset);
+
static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set,
bool shared)
{
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 23230c1d031e..a85f2dedc947 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -5,6 +5,7 @@
#include <linux/blkdev.h>
#include <linux/sbitmap.h>
#include <linux/srcu.h>
+#include <linux/rcupdate_wait.h>
struct blk_mq_tags;
struct blk_flush_queue;
@@ -170,6 +171,7 @@ struct blk_mq_hw_ctx {
*/
struct list_head hctx_list;
+ struct rcu_synchronize *rcu_sync;
/**
* @srcu: Sleepable RCU. Use as lock when type of the hardware
queue is
* blocking (BLK_MQ_F_BLOCKING). Must be the last member - see also
@@ -532,6 +534,8 @@ int blk_mq_map_queues(struct blk_mq_queue_map *qmap);
void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int
nr_hw_queues);
void blk_mq_quiesce_queue_nowait(struct request_queue *q);
+void blk_mq_quiesce_tagset(struct request_queue *q);
+void blk_mq_unquiesce_tagset(struct request_queue *q);
unsigned int blk_mq_rq_cpu(struct request *rq);
--
And then nvme will use it:
--
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 05aa568a60af..c41df20996d7 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4557,23 +4557,13 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
void nvme_stop_queues(struct nvme_ctrl *ctrl)
{
- struct nvme_ns *ns;
-
- down_read(&ctrl->namespaces_rwsem);
- list_for_each_entry(ns, &ctrl->namespaces, list)
- blk_mq_quiesce_queue(ns->queue);
- up_read(&ctrl->namespaces_rwsem);
+ blk_mq_quiesce_tagset(ctrl->tagset);
}
EXPORT_SYMBOL_GPL(nvme_stop_queues);
void nvme_start_queues(struct nvme_ctrl *ctrl)
{
- struct nvme_ns *ns;
-
- down_read(&ctrl->namespaces_rwsem);
- list_for_each_entry(ns, &ctrl->namespaces, list)
- blk_mq_unquiesce_queue(ns->queue);
- up_read(&ctrl->namespaces_rwsem);
+ blk_mq_unquiesce_tagset(ctrl->tagset);
}
EXPORT_SYMBOL_GPL(nvme_start_queues);
--
Thoughts?
_______________________________________________
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Linux-nvme@lists.infradead.org
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next prev parent reply other threads:[~2020-07-27 22:37 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 22:07 [PATCH v4 0/2] improve quiesce time for large amount of namespaces Sagi Grimberg
2020-07-27 22:07 ` Sagi Grimberg
2020-07-27 22:07 ` [PATCH v4 1/2] blk-mq: add async quiesce interface Sagi Grimberg
2020-07-27 22:07 ` Sagi Grimberg
2020-07-27 22:13 ` Jens Axboe
2020-07-27 22:13 ` Jens Axboe
2020-07-27 22:37 ` Sagi Grimberg [this message]
2020-07-27 22:37 ` Sagi Grimberg
2020-07-27 22:07 ` [PATCH v4 2/2] nvme: improve quiesce time for large amount of namespaces Sagi Grimberg
2020-07-27 22:07 ` Sagi Grimberg
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