Re: [PATCH] target: add iscsi/cpus_allowed_list in configfs

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在 2022/2/9 上午1:50, Mike Christie 写道:
On 1/25/22 2:38 AM, mingzhe.zou@xxxxxxxxxxxx wrote:
From: Mingzhe Zou <mingzhe.zou@xxxxxxxxxxxx>

The RX/TX threads for iSCSI connection can be scheduled to
any online cpus, and will not be rescheduled.

If bind other heavy load threads with iSCSI connection
RX/TX thread to the same cpu, the iSCSI performance will
be worse.

This patch add iscsi/cpus_allowed_list in configfs. The
available cpus set of iSCSI connection RX/TX threads is
allowed_cpus & online_cpus. If it is modified, all RX/TX
threads will be rescheduled.

Signed-off-by: Mingzhe Zou <mingzhe.zou@xxxxxxxxxxxx>
---
  drivers/target/iscsi/iscsi_target.c          | 21 ++++++++++--
  drivers/target/iscsi/iscsi_target.h          | 17 ++++++++++
  drivers/target/iscsi/iscsi_target_configfs.c | 34 ++++++++++++++++++++
  drivers/target/iscsi/iscsi_target_login.c    |  7 ++++
  include/target/iscsi/iscsi_target_core.h     |  1 +
  5 files changed, 78 insertions(+), 2 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index 2c54c5d8412d..a18d3fc3cfd1 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -693,6 +693,11 @@ static int __init iscsi_target_init_module(void)
  	mutex_init(&auth_id_lock);
  	idr_init(&tiqn_idr);
+ /*
+	 * allow all cpus run iscsi_ttx and iscsi_trx
I would just drop the comment. The "setall" in the function name
is pretty clear already.
I will remove it.


+	 */
+	cpumask_setall(&__iscsi_allowed_cpumask);
+
  	ret = target_register_template(&iscsi_ops);
  	if (ret)
  		goto out;
@@ -3587,6 +3592,15 @@ static int iscsit_send_reject(
  void iscsit_thread_get_cpumask(struct iscsi_conn *conn)
  {
  	int ord, cpu;
+	cpumask_t conn_allowed_cpumask;
+
+	/*
+	 * The available cpus set of iSCSI connection's RX/TX threads
+	 */
Probably can drop the comment too since the variable names make it
known what we are doing.
I will remove it.


+	cpumask_and(&conn_allowed_cpumask,
+		&__iscsi_allowed_cpumask,
+		cpu_online_mask);
The formatting needs some fix ups. I think __iscsi_allowed_cpumask can fit on the
line above it and then cpu_online_mask should be moved over a couple spaces to
align with the opening "(".

I will reformat.



+
  	/*
  	 * bitmap_id is assigned from iscsit_global->ts_bitmap from
  	 * within iscsit_start_kthreads()
@@ -3595,8 +3609,9 @@ void iscsit_thread_get_cpumask(struct iscsi_conn *conn)
  	 * iSCSI connection's RX/TX threads will be scheduled to
  	 * execute upon.
  	 */
-	ord = conn->bitmap_id % cpumask_weight(cpu_online_mask);
-	for_each_online_cpu(cpu) {
+	cpumask_clear(conn->conn_cpumask);
+	ord = conn->bitmap_id % cpumask_weight(&conn_allowed_cpumask);
+	for_each_cpu(cpu, &conn_allowed_cpumask) {
  		if (ord-- == 0) {
  			cpumask_set_cpu(cpu, conn->conn_cpumask);
  			return;
@@ -3821,6 +3836,7 @@ int iscsi_target_tx_thread(void *arg)
  		 * Ensure that both TX and RX per connection kthreads
  		 * are scheduled to run on the same CPU.
  		 */
+		iscsit_thread_reschedule(conn);

If we have multiple sessions to the same portal, could we end up racing
where session0's tx/rx threads call iscsit_thread_reschedule and
iscsit_thread_check_cpumask at the same time as session1's threads and
they end up taking the same cpus. They both could be running
iscsit_thread_get_cpumask at the same time, see he same masks values
and in the for_each_cpu loop think the same cpu is free.

Simply, this patch just adds a config item to skip some CPUs that are bound to other threads,

not to change the calculation method of cpumask.

When the cpus_allowed_list in sysfs is modified, the tx/rx threads of all sessions will clear current

cpumask and call iscsit_thread_reschedule and iscsit_thread_check_cpumask to get a new value.

Because each session is allocated a unique bitmap_id in advance, then calculate the cpumask

via bitmap_id. So the tx/rx threads of different sessions will be scheduled to different CPUs (when

the number of CPUs is sufficient).



  		iscsit_thread_check_cpumask(conn, current, 1);
wait_event_interruptible(conn->queues_wq,
@@ -3966,6 +3982,7 @@ static void iscsit_get_rx_pdu(struct iscsi_conn *conn)
  		 * Ensure that both TX and RX per connection kthreads
  		 * are scheduled to run on the same CPU.
  		 */
+		iscsit_thread_reschedule(conn);
  		iscsit_thread_check_cpumask(conn, current, 0);
memset(&iov, 0, sizeof(struct kvec));
diff --git a/drivers/target/iscsi/iscsi_target.h b/drivers/target/iscsi/iscsi_target.h
index b35a96ded9c1..cb97a316d76d 100644
--- a/drivers/target/iscsi/iscsi_target.h
+++ b/drivers/target/iscsi/iscsi_target.h
@@ -57,4 +57,21 @@ extern struct kmem_cache *lio_r2t_cache;
  extern struct ida sess_ida;
  extern struct mutex auth_id_lock;
+extern cpumask_t __iscsi_allowed_cpumask;
I would rename to:

iscsit_allowed_cpumask

I will rename to iscsit_allowed_cpumas.
+
+static inline void iscsit_thread_reschedule(struct iscsi_conn *conn)
+{
+	/*
+	 * If __iscsi_allowed_cpumask modified, reschedule iSCSI connection's
+	 * RX/TX threads update conn->allowed_cpumask.
+	 */
+	if (!cpumask_equal(&__iscsi_allowed_cpumask, conn->allowed_cpumask)) {
+		iscsit_thread_get_cpumask(conn);
+		conn->conn_tx_reset_cpumask = 1;
+		conn->conn_rx_reset_cpumask = 1;
+		cpumask_copy(conn->allowed_cpumask,
+			&__iscsi_allowed_cpumask);
Fix up formatting like above.
I will reformat.

+	}
+}
+
  #endif   /*** ISCSI_TARGET_H ***/
diff --git a/drivers/target/iscsi/iscsi_target_configfs.c b/drivers/target/iscsi/iscsi_target_configfs.c
index 2a9de24a8bbe..dc12b1695838 100644
--- a/drivers/target/iscsi/iscsi_target_configfs.c
+++ b/drivers/target/iscsi/iscsi_target_configfs.c
@@ -1127,8 +1127,42 @@ static ssize_t lio_target_wwn_lio_version_show(struct config_item *item,
CONFIGFS_ATTR_RO(lio_target_wwn_, lio_version); +cpumask_t __iscsi_allowed_cpumask;
Maybe better to put this in iscsi_target.c with the other vars like
it.

Originally I wanted to put it in struct iscsit_global and use it in iscsit_thread_check_cpumask.

However iscsit_thread_check_cpumask is also called in cxgbit_target.c. I don't know if I also

need to modify cxgbit at the same time, and I only modified two calls in iscsi_target.c. I would

like to know how to handle in cxgbit_target.c?

I want to move 'static inline void iscsit_thread_check_cpumask' from iscsi_target_core.h to

iscsi_target.c and EXPORT_SYMBOL(iscsit_thread_check_cpumask). Do you agree it?


+
+static ssize_t lio_target_wwn_cpus_allowed_list_show(
+		struct config_item *item, char *page)
+{
+	return sprintf(page, "%*pbl\n",
+		cpumask_pr_args(&__iscsi_allowed_cpumask));
Formatting like above.
I will reformat.

+}
+
+static ssize_t lio_target_wwn_cpus_allowed_list_store(
+		struct config_item *item, const char *page, size_t count)
+{
+	int ret;
+	char *orig;
+	cpumask_t new_allowed_cpumask;
+
+	orig = kstrdup(page, GFP_KERNEL);
+	if (!orig)
+		return -ENOMEM;
+
+	cpumask_clear(&new_allowed_cpumask);
+	ret = cpulist_parse(orig, &new_allowed_cpumask);
Are you supposed to do a  before
using new_allowed_cpumask? It looks like other callers are doing it.

Other callers used cpumask_var_t, but the new_allowed_cpumask is cpumask_t.

I think just call cpumask_clear(&new_allowed_cpumask).


typedef struct cpumask { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t;

typedef struct cpumask cpumask_var_t[1];


+
+	kfree(orig);
+	if (ret != 0)
+		return ret;
+
+	cpumask_copy(&__iscsi_allowed_cpumask, &new_allowed_cpumask);
+	return count;
+}
+
+CONFIGFS_ATTR(lio_target_wwn_, cpus_allowed_list);
+
  static struct configfs_attribute *lio_target_wwn_attrs[] = {
  	&lio_target_wwn_attr_lio_version,
+	&lio_target_wwn_attr_cpus_allowed_list,
  	NULL,
  };
diff --git a/drivers/target/iscsi/iscsi_target_login.c b/drivers/target/iscsi/iscsi_target_login.c
index 1a9c50401bdb..910f35e4648a 100644
--- a/drivers/target/iscsi/iscsi_target_login.c
+++ b/drivers/target/iscsi/iscsi_target_login.c
@@ -1129,8 +1129,15 @@ static struct iscsi_conn *iscsit_alloc_conn(struct iscsi_np *np)
  		goto free_conn_ops;
  	}
+ if (!zalloc_cpumask_var(&conn->allowed_cpumask, GFP_KERNEL)) {
+		pr_err("Unable to allocate conn->allowed_cpumask\n");
+		goto free_conn_cpumask;
+	}
I think in iscsit_free_conn you need a:

free_cpumask_var(conn->allowed_cpumask);

to go with this allocation.
This is bug. I will fix up in v2.

+
  	return conn;
+free_conn_cpumask:
+	free_cpumask_var(conn->allowed_cpumask);
I think you wanted conn->conn_cpumask here.
This is bug. I will fix up in v2.
  free_conn_ops:
  	kfree(conn->conn_ops);
  put_transport:
diff --git a/include/target/iscsi/iscsi_target_core.h b/include/target/iscsi/iscsi_target_core.h
index 1eccb2ac7d02..c5e9cad187cf 100644
--- a/include/target/iscsi/iscsi_target_core.h
+++ b/include/target/iscsi/iscsi_target_core.h
@@ -580,6 +580,7 @@ struct iscsi_conn {
  	struct ahash_request	*conn_tx_hash;
  	/* Used for scheduling TX and RX connection kthreads */
  	cpumask_var_t		conn_cpumask;
+	cpumask_var_t		allowed_cpumask;
  	unsigned int		conn_rx_reset_cpumask:1;
  	unsigned int		conn_tx_reset_cpumask:1;
  	/* list_head of struct iscsi_cmd for this connection */




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