From: Anton Blanchard <anton@samba.org>
To: akpm@osdl.org
Cc: paulus@samba.org, linux-kernel@vger.kernel.org
Subject: [PATCH] SPLPAR spinlock optimisation
Date: Sun, 4 Jul 2004 20:11:58 +1000 [thread overview]
Message-ID: <20040704101158.GF4923@krispykreme> (raw)
Currently our spinlocks can call into the hypervisor on dedicated
processor machines. Doing this may slow our locks down, so avoid it
where possible.
Signed-off-by: Anton Blanchard <anton@samba.org>
diff -puN arch/ppc64/lib/locks.c~splpar_speedup arch/ppc64/lib/locks.c
--- foobar2/arch/ppc64/lib/locks.c~splpar_speedup 2004-07-04 19:40:39.518987541 +1000
+++ foobar2-anton/arch/ppc64/lib/locks.c 2004-07-04 19:55:27.966154716 +1000
@@ -38,6 +38,10 @@
/* waiting for a spinlock... */
#if defined(CONFIG_PPC_SPLPAR) || defined(CONFIG_PPC_ISERIES)
+
+/* We only yield to the hypervisor if we are in shared processor mode */
+#define SHARED_PROCESSOR (get_paca()->lppaca.xSharedProc)
+
void __spin_yield(spinlock_t *lock)
{
unsigned int lock_value, holder_cpu, yield_count;
@@ -65,6 +69,7 @@ void __spin_yield(spinlock_t *lock)
#else /* SPLPAR || ISERIES */
#define __spin_yield(x) barrier()
+#define SHARED_PROCESSOR 0
#endif
/*
@@ -104,7 +109,8 @@ void _raw_spin_lock(spinlock_t *lock)
break;
do {
HMT_low();
- __spin_yield(lock);
+ if (SHARED_PROCESSOR)
+ __spin_yield(lock);
} while (likely(lock->lock != 0));
HMT_medium();
}
@@ -123,7 +129,8 @@ void _raw_spin_lock_flags(spinlock_t *lo
local_irq_restore(flags);
do {
HMT_low();
- __spin_yield(lock);
+ if (SHARED_PROCESSOR)
+ __spin_yield(lock);
} while (likely(lock->lock != 0));
HMT_medium();
local_irq_restore(flags_dis);
@@ -134,8 +141,12 @@ EXPORT_SYMBOL(_raw_spin_lock_flags);
void spin_unlock_wait(spinlock_t *lock)
{
- while (lock->lock)
- __spin_yield(lock);
+ while (lock->lock) {
+ HMT_low();
+ if (SHARED_PROCESSOR)
+ __spin_yield(lock);
+ }
+ HMT_medium();
}
EXPORT_SYMBOL(spin_unlock_wait);
@@ -213,7 +224,8 @@ void _raw_read_lock(rwlock_t *rw)
break;
do {
HMT_low();
- __rw_yield(rw);
+ if (SHARED_PROCESSOR)
+ __rw_yield(rw);
} while (likely(rw->lock < 0));
HMT_medium();
}
@@ -275,7 +287,8 @@ void _raw_write_lock(rwlock_t *rw)
break;
do {
HMT_low();
- __rw_yield(rw);
+ if (SHARED_PROCESSOR)
+ __rw_yield(rw);
} while (likely(rw->lock != 0));
HMT_medium();
}
_
reply other threads:[~2004-07-04 10:15 UTC|newest]
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