From: Matthew Wilcox <willy@infradead.org>
To: paulus@samba.org, benh@kernel.crashing.org, mpe@ellerman.id.au
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Optimised memset64/memset32 for powerpc
Date: Mon, 20 Mar 2017 14:14:47 -0700 [thread overview]
Message-ID: <20170320211447.GB5073@bombadil.infradead.org> (raw)
I recently introduced memset32() / memset64(). I've done implementations
for x86 & ARM; akpm has agreed to take the patchset through his tree.
Do you fancy doing a powerpc version? Minchan Kim got a 7% performance
increase with zram from switching to the optimised version on x86.
Here's the development git tree:
http://git.infradead.org/users/willy/linux-dax.git/shortlog/refs/heads/memfill
(most recent 7 commits)
ARM probably offers the best model for you to work from; it's basically
just a case of jumping into the middle of your existing memset loop.
It was only three instructions to add support to ARM, but I don't know
PowerPC well enough to understand how your existing memset works.
I'd start with something like this ... note that you don't have to
implement memset64 on 32-bit; I only did it on ARM because it was free.
It doesn't look free for you as you only store one register each time
around the loop in the 32-bit memset implementation:
1: stwu r4,4(r6)
bdnz 1b
(wouldn't you get better performance on 32-bit powerpc by unrolling that
loop like you do on 64-bit?)
diff --git a/arch/powerpc/include/asm/string.h b/arch/powerpc/include/asm/string.h
index da3cdffca440..c02392fced98 100644
--- a/arch/powerpc/include/asm/string.h
+++ b/arch/powerpc/include/asm/string.h
@@ -6,6 +6,7 @@
#define __HAVE_ARCH_STRNCPY
#define __HAVE_ARCH_STRNCMP
#define __HAVE_ARCH_MEMSET
+#define __HAVE_ARCH_MEMSET_PLUS
#define __HAVE_ARCH_MEMCPY
#define __HAVE_ARCH_MEMMOVE
#define __HAVE_ARCH_MEMCMP
@@ -23,6 +24,18 @@ extern void * memmove(void *,const void *,__kernel_size_t);
extern int memcmp(const void *,const void *,__kernel_size_t);
extern void * memchr(const void *,int,__kernel_size_t);
+extern void *__memset32(uint32_t *, uint32_t v, __kernel_size_t);
+static inline void *memset32(uint32_t *p, uint32_t v, __kernel_size_t n)
+{
+ return __memset32(p, v, n * 4);
+}
+
+extern void *__memset64(uint64_t *, uint64_t v, __kernel_size_t);
+static inline void *memset64(uint64_t *p, uint64_t v, __kernel_size_t n)
+{
+ return __memset64(p, v, n * 8);
+}
+
#endif /* __KERNEL__ */
#endif /* _ASM_POWERPC_STRING_H */
next reply other threads:[~2017-03-20 21:15 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-20 21:14 Matthew Wilcox [this message]
2017-03-20 21:23 ` Optimised memset64/memset32 for powerpc Benjamin Herrenschmidt
2017-03-21 12:23 ` Christophe LEROY
2017-03-21 13:29 ` Matthew Wilcox
2017-03-21 16:45 ` Segher Boessenkool
2017-03-21 21:26 ` Benjamin Herrenschmidt
2017-03-22 13:18 ` Matthew Wilcox
2017-03-22 19:30 ` Matthew Wilcox
2017-03-27 19:37 ` Naveen N. Rao
2017-03-27 19:37 ` [PATCH 1/2] powerpc: string: implement optimized memset variants Naveen N. Rao
2017-03-28 0:44 ` Michael Ellerman
2017-03-28 10:21 ` Naveen N. Rao
2017-03-29 11:36 ` Michael Ellerman
2017-03-30 7:16 ` Naveen N. Rao
2017-04-04 12:00 ` Michael Ellerman
2017-04-18 6:45 ` Michael Ellerman
2017-04-05 5:51 ` PrasannaKumar Muralidharan
2017-04-12 15:05 ` Naveen N. Rao
2017-08-18 12:50 ` [1/2] " Michael Ellerman
2017-03-27 19:37 ` [PATCH 2/2] powerpc: bpf: use memset32() to pre-fill traps in BPF page(s) Naveen N. Rao
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