diff options
| author | Tom Lane <tgl@sss.pgh.pa.us> | 2012-01-01 22:39:59 -0500 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2012-01-02 00:02:00 -0500 |
| commit | 5cfa8dd3007d7e953c6a03b0fa2215d97c581b0c (patch) | |
| tree | 39ee2902ec30be8467b91a25f3f02c7a89f70507 /src/include/storage/s_lock.h | |
| parent | 6b6137e4efebcd767a349099b3e048fbc7755cca (diff) | |
Use mutex hint bit in PPC LWARX instructions, where possible.
The hint bit makes for a small but measurable performance improvement
in access to contended spinlocks.
On the other hand, some PPC chips give an illegal-instruction failure.
There doesn't seem to be a completely bulletproof way to tell whether the
hint bit will cause an illegal-instruction failure other than by trying
it; but most if not all 64-bit PPC machines should accept it, so follow
the Linux kernel's lead and assume it's okay to use it in 64-bit builds.
Of course we must also check whether the assembler accepts the command,
since even with a recent CPU the toolchain could be old.
Patch by Manabu Ori, significantly modified by me.
Diffstat (limited to 'src/include/storage/s_lock.h')
| -rw-r--r-- | src/include/storage/s_lock.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h index 98c12db3ab3..cc67be81eb3 100644 --- a/src/include/storage/s_lock.h +++ b/src/include/storage/s_lock.h @@ -372,7 +372,11 @@ tas(volatile slock_t *lock) int _res; __asm__ __volatile__( +#ifdef USE_PPC_LWARX_MUTEX_HINT +" lwarx %0,0,%3,1 \n" +#else " lwarx %0,0,%3 \n" +#endif " cmpwi %0,0 \n" " bne 1f \n" " addi %0,%0,1 \n" |