aboutsummaryrefslogtreecommitdiff
path: root/arch/powerpc/include
diff options
context:
space:
mode:
authorNicholas Piggin <npiggin@gmail.com>2017-01-04 04:58:28 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2017-02-18 14:40:01 +1100
commitd11914b21c4c21a294fe8937d66c1a192caa3cad (patch)
treec4b6822062b0d542c772979eb05ba20abbdae3f8 /arch/powerpc/include
parent02983449c87b1dfd9b75af4c8a2a8057f9664c08 (diff)
downloadlinux-stericsson-d11914b21c4c21a294fe8937d66c1a192caa3cad.tar.gz
powerpc/64: Implement clear_bit_unlock_is_negative_byte()
Commit b91e1302ad9b8 ("mm: optimize PageWaiters bit use for unlock_page()") added a special bitop function to speed up unlock_page(). Implement this for 64-bit powerpc. This improves the unlock_page() core code from this: li 9,1 lwsync 1: ldarx 10,0,3,0 andc 10,10,9 stdcx. 10,0,3 bne- 1b ori 2,2,0 ld 9,0(3) andi. 10,9,0x80 beqlr li 4,0 b wake_up_page_bit To this: li 10,1 lwsync 1: ldarx 9,0,3,0 andc 9,9,10 stdcx. 9,0,3 bne- 1b andi. 10,9,0x80 beqlr li 4,0 b wake_up_page_bit In a test of elapsed time for dd writing into 16GB of already-dirty pagecache on a POWER8 with 4K pages, which has one unlock_page per 4kB this patch reduced overhead by 1.1%: N Min Max Median Avg Stddev x 19 2.578 2.619 2.594 2.595 0.011 + 19 2.552 2.592 2.564 2.565 0.008 Difference at 95.0% confidence -0.030 +/- 0.006 -1.142% +/- 0.243% Signed-off-by: Nicholas Piggin <npiggin@gmail.com> [mpe: Made 64-bit only until I can test it properly on 32-bit] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/include')
-rw-r--r--arch/powerpc/include/asm/bitops.h28
1 files changed, 28 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/bitops.h b/arch/powerpc/include/asm/bitops.h
index 59abc620f8e8..73eb794d6163 100644
--- a/arch/powerpc/include/asm/bitops.h
+++ b/arch/powerpc/include/asm/bitops.h
@@ -154,6 +154,34 @@ static __inline__ int test_and_change_bit(unsigned long nr,
return test_and_change_bits(BIT_MASK(nr), addr + BIT_WORD(nr)) != 0;
}
+#ifdef CONFIG_PPC64
+static __inline__ unsigned long clear_bit_unlock_return_word(int nr,
+ volatile unsigned long *addr)
+{
+ unsigned long old, t;
+ unsigned long *p = (unsigned long *)addr + BIT_WORD(nr);
+ unsigned long mask = BIT_MASK(nr);
+
+ __asm__ __volatile__ (
+ PPC_RELEASE_BARRIER
+"1:" PPC_LLARX(%0,0,%3,0) "\n"
+ "andc %1,%0,%2\n"
+ PPC405_ERR77(0,%3)
+ PPC_STLCX "%1,0,%3\n"
+ "bne- 1b\n"
+ : "=&r" (old), "=&r" (t)
+ : "r" (mask), "r" (p)
+ : "cc", "memory");
+
+ return old;
+}
+
+/* This is a special function for mm/filemap.c */
+#define clear_bit_unlock_is_negative_byte(nr, addr) \
+ (clear_bit_unlock_return_word(nr, addr) & BIT_MASK(PG_waiters))
+
+#endif /* CONFIG_PPC64 */
+
#include <asm-generic/bitops/non-atomic.h>
static __inline__ void __clear_bit_unlock(int nr, volatile unsigned long *addr)