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Reverse the logic for ADAPTIVE_SX option and enable it by default.

Browse Source 
Introduce for this operation the reverse NO_ADAPTIVE_SX option.
The flag SX_ADAPTIVESPIN to be passed to sx_init_flags(9) gets suppressed
and the new flag, offering the reversed logic, SX_NOADAPTIVE is added.

Additively implements adaptive spininning for sx held in shared mode.
The spinning limit can be handled through sysctls in order to be tuned
while the code doesn't reach the release, after which time they should
be dropped probabilly.

This change has made been necessary by recent benchmarks where it does
improve concurrency of workloads in presence of high contention
(ie. ZFS).

KPI breakage is documented by __FreeBSD_version bumping, manpage and
UPDATING updates.

Requested by:	jeff, kmacy
Reviewed by:	jeff
Tested by:	pho
This commit is contained in:
Attilio Rao 2009-05-29 01:49:27 +00:00
parent 1a9dc239f5
commit 1ae1c2a3bd
9 changed files with 75 additions and 38 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
UPDATING
View File

@ -22,6 +22,14 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 8.x IS SLOW:
to maximize performance. (To disable malloc debugging, run
ln -s aj /etc/malloc.conf.)
20090528:
The compiling option ADAPTIVE_SX has been retired while it has been
introduced the option NO_ADAPTIVE_SX which handles the reversed logic.
The KPI for sx_init_flags() changes as accepting flags:
SX_ADAPTIVESPIN flag has been retired while the SX_NOADAPTIVE flag
has been introduced in order to handle the reversed logic.
Bump __FreeBSD_version to 800092.
20090527:
Add support for hierarchical jails. Remove global securelevel.
Bump __FreeBSD_version to 800091.

10
share/man/man9/sx.9
View File

@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd November 25, 2007
.Dd May 28, 2009
.Dt SX 9
.Os
.Sh NAME
@ -122,10 +122,10 @@ argument to
specifies a set of optional flags to alter the behavior of
.Fa sx .
It contains one or more of the following flags:
.Bl -tag -width SX_ADAPTIVESPIN
.It Dv SX_ADAPTIVESPIN
If the kernel is compiled with
.Cd "options ADAPTIVE_SX" ,
.Bl -tag -width SX_NOADAPTIVE
.It Dv SX_NOADAPTIVE
If the kernel is not compiled with
.Cd "options NO_ADAPTIVE_SX" ,
then lock operations for
.Fa sx
will spin instead of sleeping while an exclusive lock holder is executing on

4
sys/cddl/compat/opensolaris/sys/mutex.h
View File

@ -47,9 +47,9 @@ typedef enum {
typedef struct sx kmutex_t;
#ifndef DEBUG
#define MUTEX_FLAGS (SX_DUPOK | SX_NOWITNESS | SX_ADAPTIVESPIN)
#define MUTEX_FLAGS (SX_DUPOK | SX_NOWITNESS)
#else
#define MUTEX_FLAGS (SX_DUPOK | SX_ADAPTIVESPIN)
#define MUTEX_FLAGS (SX_DUPOK)
#endif
#define mutex_init(lock, desc, type, arg) do { \

4
sys/cddl/compat/opensolaris/sys/rwlock.h
View File

@ -49,9 +49,9 @@ typedef enum {
typedef struct sx krwlock_t;
#ifndef DEBUG
#define RW_FLAGS (SX_DUPOK | SX_NOWITNESS | SX_ADAPTIVESPIN)
#define RW_FLAGS (SX_DUPOK | SX_NOWITNESS)
#else
#define RW_FLAGS (SX_DUPOK | SX_ADAPTIVESPIN)
#define RW_FLAGS (SX_DUPOK)
#endif
#define RW_READ_HELD(x) (rw_read_held((x)))

10
sys/conf/NOTES
View File

@ -215,11 +215,11 @@ options NO_ADAPTIVE_MUTEXES
# to disable it.
options NO_ADAPTIVE_RWLOCKS
# ADAPTIVE_SX changes the behavior of sx locks to spin if the thread
# that currently owns the lock is executing on another CPU. Note that
# in addition to enabling this option, individual sx locks must be
# initialized with the SX_ADAPTIVESPIN flag.
options ADAPTIVE_SX
# ADAPTIVE_SX changes the behavior of sx locks to spin if the thread that
# currently owns the sx lock is executing on another CPU.
# This behaviour is enabled by default, so this option can be used to
# disable it.
options NO_ADAPTIVE_SX
# MUTEX_NOINLINE forces mutex operations to call functions to perform each
# operation rather than inlining the simple cases. This can be used to

2
sys/conf/options
View File

@ -60,7 +60,6 @@ KDB_UNATTENDED opt_kdb.h
SYSCTL_DEBUG opt_sysctl.h
# Miscellaneous options.
ADAPTIVE_SX
ALQ
AUDIT opt_global.h
CODA_COMPAT_5 opt_coda.h
@ -134,6 +133,7 @@ MPROF_BUFFERS opt_mprof.h
MPROF_HASH_SIZE opt_mprof.h
NO_ADAPTIVE_MUTEXES opt_adaptive_mutexes.h
NO_ADAPTIVE_RWLOCKS
NO_ADAPTIVE_SX
NO_SYSCTL_DESCR opt_global.h
NSWBUF_MIN opt_swap.h
MBUF_PACKET_ZONE_DISABLE opt_global.h

71
sys/kern/kern_sx.c
View File

@ -60,12 +60,12 @@ __FBSDID("$FreeBSD$");
#include <ddb/ddb.h>
#endif
#if !defined(SMP) && defined(ADAPTIVE_SX)
#error "You must have SMP to enable the ADAPTIVE_SX option"
#if defined(SMP) && !defined(NO_ADAPTIVE_SX)
#define ADAPTIVE_SX
#endif
CTASSERT(((SX_ADAPTIVESPIN | SX_RECURSE) & LO_CLASSFLAGS) ==
(SX_ADAPTIVESPIN | SX_RECURSE));
CTASSERT(((SX_NOADAPTIVE | SX_RECURSE) & LO_CLASSFLAGS) ==
(SX_NOADAPTIVE | SX_RECURSE));
/* Handy macros for sleep queues. */
#define SQ_EXCLUSIVE_QUEUE 0
@ -133,6 +133,14 @@ struct lock_class lock_class_sx = {
#define _sx_assert(sx, what, file, line)
#endif
#ifdef ADAPTIVE_SX
static u_int asx_retries = 10;
static u_int asx_loops = 10000;
SYSCTL_NODE(_debug, OID_AUTO, sx, CTLFLAG_RD, NULL, "sxlock debugging");
SYSCTL_INT(_debug_sx, OID_AUTO, retries, CTLFLAG_RW, &asx_retries, 0, "");
SYSCTL_INT(_debug_sx, OID_AUTO, loops, CTLFLAG_RW, &asx_loops, 0, "");
#endif
void
assert_sx(struct lock_object *lock, int what)
{
@ -195,7 +203,7 @@ sx_init_flags(struct sx *sx, const char *description, int opts)
int flags;
MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK |
SX_NOPROFILE | SX_ADAPTIVESPIN)) == 0);
SX_NOPROFILE | SX_NOADAPTIVE)) == 0);
flags = LO_RECURSABLE | LO_SLEEPABLE | LO_UPGRADABLE;
if (opts & SX_DUPOK)
@ -207,7 +215,7 @@ sx_init_flags(struct sx *sx, const char *description, int opts)
if (opts & SX_QUIET)
flags |= LO_QUIET;
flags |= opts & (SX_ADAPTIVESPIN | SX_RECURSE);
flags |= opts & (SX_NOADAPTIVE | SX_RECURSE);
sx->sx_lock = SX_LOCK_UNLOCKED;
sx->sx_recurse = 0;
lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags);
@ -453,6 +461,7 @@ _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
GIANT_DECLARE;
#ifdef ADAPTIVE_SX
volatile struct thread *owner;
u_int i, spintries = 0;
#endif
uintptr_t x;
#ifdef LOCK_PROFILING
@ -495,24 +504,44 @@ _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
* running or the state of the lock changes.
*/
x = sx->sx_lock;
if (!(x & SX_LOCK_SHARED) &&
(sx->lock_object.lo_flags & SX_ADAPTIVESPIN)) {
x = SX_OWNER(x);
owner = (struct thread *)x;
if (TD_IS_RUNNING(owner)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR3(KTR_LOCK,
if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) != 0) {
if ((x & SX_LOCK_SHARED) == 0) {
x = SX_OWNER(x);
owner = (struct thread *)x;
if (TD_IS_RUNNING(owner)) {
if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR3(KTR_LOCK,
"%s: spinning on %p held by %p",
__func__, sx, owner);
GIANT_SAVE();
while (SX_OWNER(sx->sx_lock) == x &&
TD_IS_RUNNING(owner)) {
__func__, sx, owner);
GIANT_SAVE();
while (SX_OWNER(sx->sx_lock) == x &&
TD_IS_RUNNING(owner)) {
cpu_spinwait();
#ifdef KDTRACE_HOOKS
spin_cnt++;
#endif
}
continue;
}
} else if (SX_SHARERS(x) && spintries < asx_retries) {
spintries++;
for (i = 0; i < asx_loops; i++) {
if (LOCK_LOG_TEST(&sx->lock_object, 0))
CTR4(KTR_LOCK,
"%s: shared spinning on %p with %u and %u",
__func__, sx, spintries, i);
GIANT_SAVE();
x = sx->sx_lock;
if ((x & SX_LOCK_SHARED) == 0 ||
SX_SHARERS(x) == 0)
break;
cpu_spinwait();
#ifdef KDTRACE_HOOKS
spin_cnt++;
#endif
}
continue;
if (i != asx_loops)
continue;
}
}
#endif
@ -538,7 +567,7 @@ _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
* again.
*/
if (!(x & SX_LOCK_SHARED) &&
(sx->lock_object.lo_flags & SX_ADAPTIVESPIN)) {
(sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) {
owner = (struct thread *)SX_OWNER(x);
if (TD_IS_RUNNING(owner)) {
sleepq_release(&sx->lock_object);
@ -752,7 +781,7 @@ _sx_slock_hard(struct sx *sx, int opts, const char *file, int line)
* the owner stops running or the state of the lock
* changes.
*/
if (sx->lock_object.lo_flags & SX_ADAPTIVESPIN) {
if ((sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) {
x = SX_OWNER(x);
owner = (struct thread *)x;
if (TD_IS_RUNNING(owner)) {
@ -796,7 +825,7 @@ _sx_slock_hard(struct sx *sx, int opts, const char *file, int line)
* changes.
*/
if (!(x & SX_LOCK_SHARED) &&
(sx->lock_object.lo_flags & SX_ADAPTIVESPIN)) {
(sx->lock_object.lo_flags & SX_NOADAPTIVE) == 0) {
owner = (struct thread *)SX_OWNER(x);
if (TD_IS_RUNNING(owner)) {
sleepq_release(&sx->lock_object);

2
sys/sys/param.h
View File

@ -57,7 +57,7 @@
* is created, otherwise 1.
*/
#undef __FreeBSD_version
#define __FreeBSD_version 800091 /* Master, propagated to newvers */
#define __FreeBSD_version 800092 /* Master, propagated to newvers */
#ifndef LOCORE
#include <sys/types.h>

2
sys/sys/sx.h
View File

@ -265,7 +265,7 @@ __sx_sunlock(struct sx *sx, const char *file, int line)
#define SX_NOPROFILE 0x02
#define SX_NOWITNESS 0x04
#define SX_QUIET 0x08
#define SX_ADAPTIVESPIN 0x10
#define SX_NOADAPTIVE 0x10
#define SX_RECURSE 0x20
/*