MIPS: Optimize spinlocks.
The current locking mechanism uses a ll/sc sequence to release a spinlock. This is slower than a wmb() followed by a store to unlock. The branching forward to .subsection 2 on sc failure slows down the contended case. So we get rid of that part too. Since we are now working on naturally aligned u16 values, we can get rid of a masking operation as the LHU already does the right thing. The ANDI are reversed for better scheduling on multi-issue CPUs On a 12 CPU 750MHz Octeon cn5750 this patch improves ipv4 UDP packet forwarding rates from 3.58*10^6 PPS to 3.99*10^6 PPS, or about 11%. Signed-off-by: David Daney <ddaney@caviumnetworks.com> To: linux-mips@linux-mips.org Patchwork: http://patchwork.linux-mips.org/patch/937/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
David Daney
committed by
Ralf Baechle
Ralf Baechle
parent
e275ed5ee9
commit
500c2e1fdb
@ -36,9 +36,9 @@
|
||||
|
||||
static inline int arch_spin_is_locked(arch_spinlock_t *lock)
|
||||
{
|
||||
unsigned int counters = ACCESS_ONCE(lock->lock);
|
||||
u32 counters = ACCESS_ONCE(lock->lock);
|
||||
|
||||
return ((counters >> 14) ^ counters) & 0x1fff;
|
||||
return ((counters >> 16) ^ counters) & 0xffff;
|
||||
}
|
||||
|
||||
#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
|
||||
@ -47,9 +47,9 @@ static inline int arch_spin_is_locked(arch_spinlock_t *lock)
|
||||
|
||||
static inline int arch_spin_is_contended(arch_spinlock_t *lock)
|
||||
{
|
||||
unsigned int counters = ACCESS_ONCE(lock->lock);
|
||||
u32 counters = ACCESS_ONCE(lock->lock);
|
||||
|
||||
return (((counters >> 14) - counters) & 0x1fff) > 1;
|
||||
return (((counters >> 16) - counters) & 0xffff) > 1;
|
||||
}
|
||||
#define arch_spin_is_contended arch_spin_is_contended
|
||||
|
||||
@ -57,6 +57,7 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
|
||||
{
|
||||
int my_ticket;
|
||||
int tmp;
|
||||
int inc = 0x10000;
|
||||
|
||||
if (R10000_LLSC_WAR) {
|
||||
__asm__ __volatile__ (
|
||||
@ -64,25 +65,24 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
|
||||
" .set noreorder \n"
|
||||
" \n"
|
||||
"1: ll %[ticket], %[ticket_ptr] \n"
|
||||
" addiu %[my_ticket], %[ticket], 0x4000 \n"
|
||||
" addu %[my_ticket], %[ticket], %[inc] \n"
|
||||
" sc %[my_ticket], %[ticket_ptr] \n"
|
||||
" beqzl %[my_ticket], 1b \n"
|
||||
" nop \n"
|
||||
" srl %[my_ticket], %[ticket], 14 \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0x1fff \n"
|
||||
" andi %[ticket], %[ticket], 0x1fff \n"
|
||||
" srl %[my_ticket], %[ticket], 16 \n"
|
||||
" andi %[ticket], %[ticket], 0xffff \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0xffff \n"
|
||||
" bne %[ticket], %[my_ticket], 4f \n"
|
||||
" subu %[ticket], %[my_ticket], %[ticket] \n"
|
||||
"2: \n"
|
||||
" .subsection 2 \n"
|
||||
"4: andi %[ticket], %[ticket], 0x1fff \n"
|
||||
"4: andi %[ticket], %[ticket], 0xffff \n"
|
||||
" sll %[ticket], 5 \n"
|
||||
" \n"
|
||||
"6: bnez %[ticket], 6b \n"
|
||||
" subu %[ticket], 1 \n"
|
||||
" \n"
|
||||
" lw %[ticket], %[ticket_ptr] \n"
|
||||
" andi %[ticket], %[ticket], 0x1fff \n"
|
||||
" lhu %[ticket], %[serving_now_ptr] \n"
|
||||
" beq %[ticket], %[my_ticket], 2b \n"
|
||||
" subu %[ticket], %[my_ticket], %[ticket] \n"
|
||||
" b 4b \n"
|
||||
@ -90,36 +90,33 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
|
||||
" .previous \n"
|
||||
" .set pop \n"
|
||||
: [ticket_ptr] "+m" (lock->lock),
|
||||
[serving_now_ptr] "+m" (lock->h.serving_now),
|
||||
[ticket] "=&r" (tmp),
|
||||
[my_ticket] "=&r" (my_ticket));
|
||||
[my_ticket] "=&r" (my_ticket)
|
||||
: [inc] "r" (inc));
|
||||
} else {
|
||||
__asm__ __volatile__ (
|
||||
" .set push # arch_spin_lock \n"
|
||||
" .set noreorder \n"
|
||||
" \n"
|
||||
" ll %[ticket], %[ticket_ptr] \n"
|
||||
"1: addiu %[my_ticket], %[ticket], 0x4000 \n"
|
||||
"1: ll %[ticket], %[ticket_ptr] \n"
|
||||
" addu %[my_ticket], %[ticket], %[inc] \n"
|
||||
" sc %[my_ticket], %[ticket_ptr] \n"
|
||||
" beqz %[my_ticket], 3f \n"
|
||||
" nop \n"
|
||||
" srl %[my_ticket], %[ticket], 14 \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0x1fff \n"
|
||||
" andi %[ticket], %[ticket], 0x1fff \n"
|
||||
" beqz %[my_ticket], 1b \n"
|
||||
" srl %[my_ticket], %[ticket], 16 \n"
|
||||
" andi %[ticket], %[ticket], 0xffff \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0xffff \n"
|
||||
" bne %[ticket], %[my_ticket], 4f \n"
|
||||
" subu %[ticket], %[my_ticket], %[ticket] \n"
|
||||
"2: \n"
|
||||
" .subsection 2 \n"
|
||||
"3: b 1b \n"
|
||||
" ll %[ticket], %[ticket_ptr] \n"
|
||||
" \n"
|
||||
"4: andi %[ticket], %[ticket], 0x1fff \n"
|
||||
" sll %[ticket], 5 \n"
|
||||
" \n"
|
||||
"6: bnez %[ticket], 6b \n"
|
||||
" subu %[ticket], 1 \n"
|
||||
" \n"
|
||||
" lw %[ticket], %[ticket_ptr] \n"
|
||||
" andi %[ticket], %[ticket], 0x1fff \n"
|
||||
" lhu %[ticket], %[serving_now_ptr] \n"
|
||||
" beq %[ticket], %[my_ticket], 2b \n"
|
||||
" subu %[ticket], %[my_ticket], %[ticket] \n"
|
||||
" b 4b \n"
|
||||
@ -127,8 +124,10 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
|
||||
" .previous \n"
|
||||
" .set pop \n"
|
||||
: [ticket_ptr] "+m" (lock->lock),
|
||||
[serving_now_ptr] "+m" (lock->h.serving_now),
|
||||
[ticket] "=&r" (tmp),
|
||||
[my_ticket] "=&r" (my_ticket));
|
||||
[my_ticket] "=&r" (my_ticket)
|
||||
: [inc] "r" (inc));
|
||||
}
|
||||
|
||||
smp_llsc_mb();
|
||||
@ -136,47 +135,16 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
|
||||
|
||||
static inline void arch_spin_unlock(arch_spinlock_t *lock)
|
||||
{
|
||||
int tmp;
|
||||
|
||||
smp_mb__before_llsc();
|
||||
|
||||
if (R10000_LLSC_WAR) {
|
||||
__asm__ __volatile__ (
|
||||
" # arch_spin_unlock \n"
|
||||
"1: ll %[ticket], %[ticket_ptr] \n"
|
||||
" addiu %[ticket], %[ticket], 1 \n"
|
||||
" ori %[ticket], %[ticket], 0x2000 \n"
|
||||
" xori %[ticket], %[ticket], 0x2000 \n"
|
||||
" sc %[ticket], %[ticket_ptr] \n"
|
||||
" beqzl %[ticket], 1b \n"
|
||||
: [ticket_ptr] "+m" (lock->lock),
|
||||
[ticket] "=&r" (tmp));
|
||||
} else {
|
||||
__asm__ __volatile__ (
|
||||
" .set push # arch_spin_unlock \n"
|
||||
" .set noreorder \n"
|
||||
" \n"
|
||||
" ll %[ticket], %[ticket_ptr] \n"
|
||||
"1: addiu %[ticket], %[ticket], 1 \n"
|
||||
" ori %[ticket], %[ticket], 0x2000 \n"
|
||||
" xori %[ticket], %[ticket], 0x2000 \n"
|
||||
" sc %[ticket], %[ticket_ptr] \n"
|
||||
" beqz %[ticket], 2f \n"
|
||||
" nop \n"
|
||||
" \n"
|
||||
" .subsection 2 \n"
|
||||
"2: b 1b \n"
|
||||
" ll %[ticket], %[ticket_ptr] \n"
|
||||
" .previous \n"
|
||||
" .set pop \n"
|
||||
: [ticket_ptr] "+m" (lock->lock),
|
||||
[ticket] "=&r" (tmp));
|
||||
}
|
||||
unsigned int serving_now = lock->h.serving_now + 1;
|
||||
wmb();
|
||||
lock->h.serving_now = (u16)serving_now;
|
||||
nudge_writes();
|
||||
}
|
||||
|
||||
static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
|
||||
{
|
||||
int tmp, tmp2, tmp3;
|
||||
int inc = 0x10000;
|
||||
|
||||
if (R10000_LLSC_WAR) {
|
||||
__asm__ __volatile__ (
|
||||
@ -184,11 +152,11 @@ static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
|
||||
" .set noreorder \n"
|
||||
" \n"
|
||||
"1: ll %[ticket], %[ticket_ptr] \n"
|
||||
" srl %[my_ticket], %[ticket], 14 \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0x1fff \n"
|
||||
" andi %[now_serving], %[ticket], 0x1fff \n"
|
||||
" srl %[my_ticket], %[ticket], 16 \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0xffff \n"
|
||||
" andi %[now_serving], %[ticket], 0xffff \n"
|
||||
" bne %[my_ticket], %[now_serving], 3f \n"
|
||||
" addiu %[ticket], %[ticket], 0x4000 \n"
|
||||
" addu %[ticket], %[ticket], %[inc] \n"
|
||||
" sc %[ticket], %[ticket_ptr] \n"
|
||||
" beqzl %[ticket], 1b \n"
|
||||
" li %[ticket], 1 \n"
|
||||
@ -201,33 +169,33 @@ static inline unsigned int arch_spin_trylock(arch_spinlock_t *lock)
|
||||
: [ticket_ptr] "+m" (lock->lock),
|
||||
[ticket] "=&r" (tmp),
|
||||
[my_ticket] "=&r" (tmp2),
|
||||
[now_serving] "=&r" (tmp3));
|
||||
[now_serving] "=&r" (tmp3)
|
||||
: [inc] "r" (inc));
|
||||
} else {
|
||||
__asm__ __volatile__ (
|
||||
" .set push # arch_spin_trylock \n"
|
||||
" .set noreorder \n"
|
||||
" \n"
|
||||
" ll %[ticket], %[ticket_ptr] \n"
|
||||
"1: srl %[my_ticket], %[ticket], 14 \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0x1fff \n"
|
||||
" andi %[now_serving], %[ticket], 0x1fff \n"
|
||||
"1: ll %[ticket], %[ticket_ptr] \n"
|
||||
" srl %[my_ticket], %[ticket], 16 \n"
|
||||
" andi %[my_ticket], %[my_ticket], 0xffff \n"
|
||||
" andi %[now_serving], %[ticket], 0xffff \n"
|
||||
" bne %[my_ticket], %[now_serving], 3f \n"
|
||||
" addiu %[ticket], %[ticket], 0x4000 \n"
|
||||
" addu %[ticket], %[ticket], %[inc] \n"
|
||||
" sc %[ticket], %[ticket_ptr] \n"
|
||||
" beqz %[ticket], 4f \n"
|
||||
" beqz %[ticket], 1b \n"
|
||||
" li %[ticket], 1 \n"
|
||||
"2: \n"
|
||||
" .subsection 2 \n"
|
||||
"3: b 2b \n"
|
||||
" li %[ticket], 0 \n"
|
||||
"4: b 1b \n"
|
||||
" ll %[ticket], %[ticket_ptr] \n"
|
||||
" .previous \n"
|
||||
" .set pop \n"
|
||||
: [ticket_ptr] "+m" (lock->lock),
|
||||
[ticket] "=&r" (tmp),
|
||||
[my_ticket] "=&r" (tmp2),
|
||||
[now_serving] "=&r" (tmp3));
|
||||
[now_serving] "=&r" (tmp3)
|
||||
: [inc] "r" (inc));
|
||||
}
|
||||
|
||||
smp_llsc_mb();
|
||||
|
||||
Reference in New Issue
Block a user