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/*-
* Copyright (c) 2014-2015 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
#if SPINLOCK_TYPE == SPINLOCK_PTHREAD_MUTEX_LOGGING
/*
* __wt_spin_lock_register_lock --
* Add a lock to the connection's list.
*/
int
__wt_spin_lock_register_lock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_CONNECTION_IMPL *conn;
u_int i;
/*
* There is a spinlock we initialize before we have a connection, the
* global library lock. In that case, the session will be NULL and
* we can't track the lock.
*/
if (session == NULL)
return (0);
conn = S2C(session);
for (i = 0; i < WT_SPINLOCK_MAX; i++)
if (conn->spinlock_list[i] == NULL &&
WT_ATOMIC_CAS(conn->spinlock_list[i], NULL, t))
return (0);
WT_RET_MSG(session, ENOMEM,
"spinlock connection registry failed, increase the connection's "
"spinlock list size");
}
/*
* __wt_spin_lock_unregister_lock --
* Remove a lock from the connection's list.
*/
void
__wt_spin_lock_unregister_lock(WT_SESSION_IMPL *session, WT_SPINLOCK *t)
{
WT_CONNECTION_IMPL *conn;
u_int i;
conn = S2C(session);
for (i = 0; i < WT_SPINLOCK_MAX; i++)
if (conn->spinlock_list[i] == t)
conn->spinlock_list[i] = NULL;
/*
* XXX
* The statistics thread reads through this array, there's a possible
* race: if that thread reads the pointer then goes to sleep, then we
* free the spinlock, then the statistics thread wakes up, it can read
* free'd memory.
*
* This is performance debugging code, so we're not fixing the race for
* now, minimize the window.
*/
WT_FULL_BARRIER();
}
/*
* __spin_lock_next_id --
* Return the next spinlock caller ID.
*/
static int
__spin_lock_next_id(WT_SESSION_IMPL *session, int *idp)
{
static int lock_id = 0, next_id = 0;
WT_DECL_RET;
/* If we've ever registered this location, we already have an ID. */
if (*idp != WT_SPINLOCK_REGISTER)
return (0);
/*
* We can't use the global spinlock to lock the ID allocation (duh!),
* use a CAS instruction to serialize access to a local variable.
* This work only gets done once per library instantiation, there
* isn't a performance concern.
*/
while (!WT_ATOMIC_CAS(lock_id, 0, 1))
__wt_yield();
/* Allocate a blocking ID for this location. */
if (*idp == WT_SPINLOCK_REGISTER) {
if (next_id < WT_SPINLOCK_MAX_LOCATION_ID)
*idp = next_id++;
else
WT_ERR_MSG(session, ENOMEM,
"spinlock caller location registry failed, "
"increase the connection's blocking matrix size");
}
err: WT_PUBLISH(lock_id, 0);
return (ret);
}
/*
* __wt_spin_lock_register_caller --
* Register a spin-lock caller's location information in the blocking
* matrix.
*/
int
__wt_spin_lock_register_caller(WT_SESSION_IMPL *session,
const char *name, const char *file, int line, int *idp)
{
WT_CONNECTION_IMPL *conn;
WT_CONNECTION_STATS_SPINLOCK *p;
conn = S2C(session);
/*
* The caller's location ID is a static offset into a per-connection
* structure, and that has problems: first, if there are multiple
* connections, we'll need to hold some kind of lock to avoid racing
* when setting that value, and second, if/when there are multiple
* connections and/or a single connection is closed and re-opened, the
* variable may be initialized and underlying connection information
* may not.
*
* First, allocate a location ID if needed.
*/
WT_RET(__spin_lock_next_id(session, idp));
/*
* Add the caller's information to the blocking matrix. We could race
* here (if two threads of control register the same lock at the same
* time), but we don't care as both threads are setting the identical
* information.
*/
p = &conn->spinlock_block[*idp];
p->name = name;
if ((p->file = strrchr(file, '/')) == NULL)
p->file = file;
else
++p->file;
p->line = line;
return (0);
}
/*
* __wt_statlog_dump_spinlock --
* Log the spin-lock statistics.
*/
int
__wt_statlog_dump_spinlock(WT_CONNECTION_IMPL *conn, const char *tag)
{
WT_SPINLOCK *spin;
WT_CONNECTION_STATS_SPINLOCK *p, *t;
uint64_t block_manager, btree_page, ignore;
u_int i, j;
/*
* Ignore rare acquisition of a spinlock using a base value of 10 per
* second so we don't create graphs we don't care about.
*/
ignore = (uint64_t)(conn->stat_usecs / 1000000) * 10;
/* Output the number of times each spinlock was acquired. */
block_manager = btree_page = 0;
for (i = 0; i < WT_ELEMENTS(conn->spinlock_list); ++i) {
if ((spin = conn->spinlock_list[i]) == NULL)
continue;
/*
* There are two sets of spinlocks we aggregate, the btree page
* locks and the block manager per-file locks. The reason is
* the block manager locks grow with the number of files open
* (and LSM and bloom filters can open a lot of files), and
* there are 16 btree page locks and splitting them out has not
* historically been that informative.
*/
if (strcmp(spin->name, "block manager") == 0) {
block_manager += spin->counter;
if (FLD_ISSET(conn->stat_flags, WT_CONN_STAT_CLEAR))
spin->counter = 0;
continue;
}
if (strcmp(spin->name, "btree page") == 0) {
btree_page += spin->counter;
if (FLD_ISSET(conn->stat_flags, WT_CONN_STAT_CLEAR))
spin->counter = 0;
continue;
}
WT_RET(__wt_fprintf(session, conn->stat_fp,
"%s %" PRIu64 " %s spinlock %s: acquisitions\n",
conn->stat_stamp,
spin->counter <= ignore ? 0 : spin->counter,
tag, spin->name));
if (FLD_ISSET(conn->stat_flags, WT_CONN_STAT_CLEAR))
spin->counter = 0;
}
WT_RET(__wt_fprintf(session, conn->stat_fp,
"%s %" PRIu64 " %s spinlock %s: acquisitions\n",
conn->stat_stamp,
block_manager <= ignore ? 0 : block_manager,
tag, "block manager"));
WT_RET(__wt_fprintf(session, conn->stat_fp,
"%s %" PRIu64 " %s spinlock %s: acquisitions\n",
conn->stat_stamp,
btree_page <= ignore ? 0 : btree_page,
tag, "btree page"));
/*
* Output the number of times each location acquires its spinlock and
* the blocking matrix.
*/
for (i = 0; i < WT_ELEMENTS(conn->spinlock_block); ++i) {
p = &conn->spinlock_block[i];
if (p->name == NULL)
continue;
WT_RET(__wt_fprintf(session, conn->stat_fp,
"%s %d %s spinlock %s acquired by %s(%d)\n",
conn->stat_stamp,
p->total <= ignore ? 0 : p->total,
tag,
p->name, p->file, p->line));
if (FLD_ISSET(conn->stat_flags, WT_CONN_STAT_CLEAR))
p->total = 0;
for (j = 0; j < WT_ELEMENTS(conn->spinlock_block); ++j) {
t = &conn->spinlock_block[j];
if (t->name == NULL)
continue;
WT_RET(__wt_fprintf(session, conn->stat_fp,
"%s %d %s spinlock %s: %s(%d) blocked by %s(%d)\n",
conn->stat_stamp,
p->blocked[j] <= ignore ? 0 : p->blocked[j],
tag,
p->name, p->file, p->line,
t->file, t->line));
if (FLD_ISSET(conn->stat_flags, WT_CONN_STAT_CLEAR))
p->blocked[j] = 0;
}
}
WT_FULL_BARRIER(); /* Minimize the window. */
return (0);
}
#endif /* SPINLOCK_PTHREAD_MUTEX_LOGGING */
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