pg.ddx.io pgsql-hackers@postgresql.org mailing list archive help / color / mirror / Atom feed From: Jesper Pedersen <jesper.pedersen@redhat.com>
To: pgsql-hackers@postgresql.org <pgsql-hackers@postgresql.org>
Subject: Re: Additional LWLOCK_STATS statistics
Date: Wed, 16 Dec 2015 05:02:39 -0500
Message-ID: <567136BF.6080804@redhat.com> (raw )
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On 09/16/2015 12:44 PM, Jesper Pedersen wrote:
> So, I think there is some value in keeping this information separate.
>
Just a rebased patch after the excellent LWLockTranche work.
And a new sample report with -c/-j 200 -M prepared.
Best regards,
Jesper
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Attachments:
lwstats_v4.patch (text/x-patch, 4.5K) download
From 6f03263910713b66af548b86389ce842cb048caa Mon Sep 17 00:00:00 2001
From: Jesper Pedersen <jesper.pedersen@redhat.com>
Date: Fri, 11 Dec 2015 05:52:29 -0500
Subject: [PATCH] Additional LWLOCK_STATS statistics
---
src/backend/storage/lmgr/lwlock.c | 83 ++++++++++++++++++++++++++++++++++++---
1 file changed, 77 insertions(+), 6 deletions(-)
diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index d43fb61..50d8465 100644
--- a/src/backend/storage/lmgr/lwlock.c
+++ b/src/backend/storage/lmgr/lwlock.c
@@ -158,10 +158,13 @@ typedef struct lwlock_stats
{
lwlock_stats_key key;
int sh_acquire_count;
+ int sh_acquire_max;
int ex_acquire_count;
+ int ex_acquire_max;
int block_count;
int dequeue_self_count;
int spin_delay_count;
+ int max_waiters;
} lwlock_stats;
static HTAB *lwlock_stats_htab;
@@ -292,12 +295,26 @@ print_lwlock_stats(int code, Datum arg)
while ((lwstats = (lwlock_stats *) hash_seq_search(&scan)) != NULL)
{
- fprintf(stderr,
- "PID %d lwlock %s %d: shacq %u exacq %u blk %u spindelay %u dequeue self %u\n",
- MyProcPid, LWLockTrancheArray[lwstats->key.tranche]->name,
- lwstats->key.instance, lwstats->sh_acquire_count,
- lwstats->ex_acquire_count, lwstats->block_count,
- lwstats->spin_delay_count, lwstats->dequeue_self_count);
+ if (lwstats->key.tranche == 0 && lwstats->key.instance < NUM_INDIVIDUAL_LWLOCKS)
+ {
+ /* We ignore information from MainLWLockArray[0] since it isn't in real use */
+ if (lwstats->key.instance != 0)
+ fprintf(stderr,
+ "PID %d lwlock %s: shacq %u shmax %u exacq %u exmax %u blk %u spindelay %u dequeue self %u maxw %u\n",
+ MyProcPid, MainLWLockNames[lwstats->key.instance],
+ lwstats->sh_acquire_count, lwstats->sh_acquire_max,
+ lwstats->ex_acquire_count, lwstats->ex_acquire_max,
+ lwstats->block_count, lwstats->spin_delay_count, lwstats->dequeue_self_count,
+ lwstats->max_waiters);
+ }
+ else
+ fprintf(stderr,
+ "PID %d lwlock %s %d: shacq %u shmax %u exacq %u exmax %u blk %u spindelay %u dequeue self %u maxw %u\n",
+ MyProcPid, LWLockTrancheArray[lwstats->key.tranche]->name,
+ lwstats->key.instance, lwstats->sh_acquire_count, lwstats->sh_acquire_max,
+ lwstats->ex_acquire_count, lwstats->ex_acquire_max,
+ lwstats->block_count, lwstats->spin_delay_count, lwstats->dequeue_self_count,
+ lwstats->max_waiters);
}
LWLockRelease(&MainLWLockArray[0].lock);
@@ -325,10 +342,13 @@ get_lwlock_stats_entry(LWLock *lock)
if (!found)
{
lwstats->sh_acquire_count = 0;
+ lwstats->sh_acquire_max = 0;
lwstats->ex_acquire_count = 0;
+ lwstats->ex_acquire_max = 0;
lwstats->block_count = 0;
lwstats->dequeue_self_count = 0;
lwstats->spin_delay_count = 0;
+ lwstats->max_waiters = 0;
}
return lwstats;
}
@@ -753,6 +773,9 @@ static void
LWLockQueueSelf(LWLock *lock, LWLockMode mode)
{
#ifdef LWLOCK_STATS
+ bool include;
+ int counter, size;
+ dlist_iter iter;
lwlock_stats *lwstats;
lwstats = get_lwlock_stats_entry(lock);
@@ -771,6 +794,46 @@ LWLockQueueSelf(LWLock *lock, LWLockMode mode)
#ifdef LWLOCK_STATS
lwstats->spin_delay_count += SpinLockAcquire(&lock->mutex);
+
+ /*
+ * We scan the list of waiters from the back in order to find
+ * out how many of the same lock type are waiting for a lock.
+ * Similar types have the potential to be groupped together.
+ *
+ * We also count the number of waiters, including ourself.
+ */
+ include = true;
+ size = 1;
+ counter = 1;
+
+ dlist_reverse_foreach(iter, &lock->waiters)
+ {
+ if (include)
+ {
+ PGPROC *waiter = dlist_container(PGPROC, lwWaitLink, iter.cur);
+
+ if (waiter->lwWaitMode == mode)
+ counter += 1;
+ else
+ include = false;
+ }
+
+ size += 1;
+ }
+
+ if (mode == LW_EXCLUSIVE || mode == LW_WAIT_UNTIL_FREE)
+ {
+ if (counter > lwstats->ex_acquire_max)
+ lwstats->ex_acquire_max = counter;
+ }
+ else if (mode == LW_SHARED)
+ {
+ if (counter > lwstats->sh_acquire_max)
+ lwstats->sh_acquire_max = counter;
+ }
+
+ if (size > lwstats->max_waiters)
+ lwstats->max_waiters = size;
#else
SpinLockAcquire(&lock->mutex);
#endif
@@ -922,9 +985,17 @@ LWLockAcquire(LWLock *lock, LWLockMode mode)
#ifdef LWLOCK_STATS
/* Count lock acquisition attempts */
if (mode == LW_EXCLUSIVE)
+ {
lwstats->ex_acquire_count++;
+ if (lwstats->ex_acquire_max == 0)
+ lwstats->ex_acquire_max = 1;
+ }
else
+ {
lwstats->sh_acquire_count++;
+ if (lwstats->sh_acquire_max == 0)
+ lwstats->sh_acquire_max = 1;
+ }
#endif /* LWLOCK_STATS */
/*
--
2.1.0
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To: pgsql-hackers@postgresql.org
Cc: jesper.pedersen@redhat.com
Subject: Re: Additional LWLOCK_STATS statistics
In-Reply-To: <567136BF.6080804@redhat.com>
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