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Add "options ADAPTIVE_GIANT" which causes Giant to also be treated in

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an adaptive fashion when adaptive mutexes are enabled.  The theory
behind non-adaptive Giant is that Giant will be held for long periods
of time, and therefore spinning waiting on it is wasteful.  However,
in MySQL benchmarks which are relatively Giant-free, running Giant
adaptive makes an observable difference on SMP (5% transaction rate
improvement).  As such, make adaptive behavior on Giant an option so
it can be more widely benchmarked.
This commit is contained in:
Robert Watson 2004-07-27 16:34:48 +00:00
parent 8d59f4fd45
commit a9abdce44a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=132698
3 changed files with 11 additions and 0 deletions
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6
sys/conf/NOTES
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@ -173,6 +173,12 @@ options SMP # Symmetric MultiProcessor Kernel
# to disable it.
options NO_ADAPTIVE_MUTEXES
# ADAPTIVE_GIANT causes the Giant lock to also be made adaptive when
# running without NO_ADAPTIVE_MUTEXES. Normally, because Giant is assumed
# to be held for extended periods, contention on Giant will cause a thread
# to sleep rather than spinning.
options ADAPTIVE_GIANT
# MUTEX_NOINLINE forces mutex operations to call functions to perform each
# operation rather than inlining the simple cases. This can be used to
# shrink the size of the kernel text segment. Note that this behavior is

1
sys/conf/options
View File

@ -56,6 +56,7 @@ KDB_TRACE opt_kdb.h
KDB_UNATTENDED opt_kdb.h
# Miscellaneous options.
ADAPTIVE_GIANT opt_adaptive_mutexes.h
NO_ADAPTIVE_MUTEXES opt_adaptive_mutexes.h
ALQ
CODA_COMPAT_5 opt_coda.h

4
sys/kern/kern_mutex.c
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@ -509,7 +509,11 @@ _mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line)
* CPU, spin instead of blocking.
*/
owner = (struct thread *)(v & MTX_FLAGMASK);
#ifdef ADAPTIVE_GIANT
if (TD_IS_RUNNING(owner)) {
#else
if (m != &Giant && TD_IS_RUNNING(owner)) {
#endif
turnstile_release(&m->mtx_object);
while (mtx_owner(m) == owner && TD_IS_RUNNING(owner)) {
#if defined(__i386__) || defined(__amd64__)