Commit 412f34a8 authored by Waiman Long's avatar Waiman Long Committed by Ingo Molnar
Browse files

locking/qspinlock_stat: Track the no MCS node available case 



Track the number of slowpath locking operations that are being done
without any MCS node available as well renaming lock_index[123] to make
them more descriptive.

Using these stat counters is one way to find out if a code path is
being exercised.

Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: James Morse <james.morse@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: SRINIVAS <srinivas.eeda@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Link: https://lkml.kernel.org/r/1548798828-16156-3-git-send-email-longman@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent d682b596

kernel/locking/qspinlock.c

+2 −1
Original line number Diff line number Diff line
@@ -422,6 +422,7 @@ pv_queue: 
	 * simple enough.

	 */

	if (unlikely(idx >= MAX_NODES)) {

		qstat_inc(qstat_lock_no_node, true);

		while (!queued_spin_trylock(lock))

			cpu_relax();

		goto release;
@@ -432,7 +433,7 @@ pv_queue: 
	/*

	 * Keep counts of non-zero index values:

	 */

	qstat_inc(qstat_lock_idx1 + idx - 1, idx);

	qstat_inc(qstat_lock_use_node2 + idx - 1, idx);



	/*

	 * Ensure that we increment the head node->count before initialising

kernel/locking/qspinlock_stat.h

+15 −6
Original line number Diff line number Diff line
@@ -30,6 +30,13 @@ 
 *   pv_wait_node	- # of vCPU wait's at a non-head queue node

 *   lock_pending	- # of locking operations via pending code

 *   lock_slowpath	- # of locking operations via MCS lock queue

 *   lock_use_node2	- # of locking operations that use 2nd per-CPU node

 *   lock_use_node3	- # of locking operations that use 3rd per-CPU node

 *   lock_use_node4	- # of locking operations that use 4th per-CPU node

 *   lock_no_node	- # of locking operations without using per-CPU node

 *

 * Subtracting lock_use_node[234] from lock_slowpath will give you

 * lock_use_node1.

 *

 * Writing to the "reset_counters" file will reset all the above counter

 * values.
@@ -55,9 +62,10 @@ enum qlock_stats { 
	qstat_pv_wait_node,

	qstat_lock_pending,

	qstat_lock_slowpath,

	qstat_lock_idx1,

	qstat_lock_idx2,

	qstat_lock_idx3,

	qstat_lock_use_node2,

	qstat_lock_use_node3,

	qstat_lock_use_node4,

	qstat_lock_no_node,

	qstat_num,	/* Total number of statistical counters */

	qstat_reset_cnts = qstat_num,

};
@@ -85,9 +93,10 @@ static const char * const qstat_names[qstat_num + 1] = { 
	[qstat_pv_wait_node]       = "pv_wait_node",

	[qstat_lock_pending]       = "lock_pending",

	[qstat_lock_slowpath]      = "lock_slowpath",

	[qstat_lock_idx1]	   = "lock_index1",

	[qstat_lock_idx2]	   = "lock_index2",

	[qstat_lock_idx3]	   = "lock_index3",

	[qstat_lock_use_node2]	   = "lock_use_node2",

	[qstat_lock_use_node3]	   = "lock_use_node3",

	[qstat_lock_use_node4]	   = "lock_use_node4",

	[qstat_lock_no_node]	   = "lock_no_node",

	[qstat_reset_cnts]         = "reset_counters",

};

CRA Git | Maintained and supported by SUSTech CRA and CCSE