The patch titled
Subject: lib/string.c: add multibyte memset functions
has been added to the -mm tree. Its filename is
add-multibyte-memset-functions.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/add-multibyte-memset-functions.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/add-multibyte-memset-functions.patch
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------------------------------------------------------
From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Subject: lib/string.c: add multibyte memset functions
Patch series "Multibyte memset variations", v4.
A relatively common idiom we're missing is a function to fill an area of
memory with a pattern which is larger than a single byte. I first noticed
this with a zram patch which wanted to fill a page with an 'unsigned long'
value. There turn out to be quite a few places in the kernel which can
benefit from using an optimised function rather than a loop; sometimes
text size, sometimes speed, and sometimes both. The optimised PowerPC
version (not included here) improves performance by about 30% on POWER8 on
just the raw memset_l().
Most of the extra lines of code come from the three testcases I added.
This patch (of 8):
memset16(), memset32() and memset64() are like memset(), but allow the
caller to fill the destination with a value larger than a single byte.
memset_l() and memset_p() allow the caller to use unsigned long and
pointer values respectively.
Link: http://lkml.kernel.org/r/20170720184539.31609-2-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxxxxxxx>
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/string.h | 30 +++++++++++++++++
lib/string.c | 66 +++++++++++++++++++++++++++++++++++++++
2 files changed, 96 insertions(+)
diff -puN include/linux/string.h~add-multibyte-memset-functions include/linux/string.h
--- a/include/linux/string.h~add-multibyte-memset-functions
+++ a/include/linux/string.h
@@ -99,6 +99,36 @@ extern __kernel_size_t strcspn(const cha
#ifndef __HAVE_ARCH_MEMSET
extern void * memset(void *,int,__kernel_size_t);
#endif
+
+#ifndef __HAVE_ARCH_MEMSET16
+extern void *memset16(uint16_t *, uint16_t, __kernel_size_t);
+#endif
+
+#ifndef __HAVE_ARCH_MEMSET32
+extern void *memset32(uint32_t *, uint32_t, __kernel_size_t);
+#endif
+
+#ifndef __HAVE_ARCH_MEMSET64
+extern void *memset64(uint64_t *, uint64_t, __kernel_size_t);
+#endif
+
+static inline void *memset_l(unsigned long *p, unsigned long v,
+ __kernel_size_t n)
+{
+ if (BITS_PER_LONG == 32)
+ return memset32((uint32_t *)p, v, n);
+ else
+ return memset64((uint64_t *)p, v, n);
+}
+
+static inline void *memset_p(void **p, void *v, __kernel_size_t n)
+{
+ if (BITS_PER_LONG == 32)
+ return memset32((uint32_t *)p, (uintptr_t)v, n);
+ else
+ return memset64((uint64_t *)p, (uintptr_t)v, n);
+}
+
#ifndef __HAVE_ARCH_MEMCPY
extern void * memcpy(void *,const void *,__kernel_size_t);
#endif
diff -puN lib/string.c~add-multibyte-memset-functions lib/string.c
--- a/lib/string.c~add-multibyte-memset-functions
+++ a/lib/string.c
@@ -723,6 +723,72 @@ void memzero_explicit(void *s, size_t co
}
EXPORT_SYMBOL(memzero_explicit);
+#ifndef __HAVE_ARCH_MEMSET16
+/**
+ * memset16() - Fill a memory area with a uint16_t
+ * @s: Pointer to the start of the area.
+ * @v: The value to fill the area with
+ * @count: The number of values to store
+ *
+ * Differs from memset() in that it fills with a uint16_t instead
+ * of a byte. Remember that @count is the number of uint16_ts to
+ * store, not the number of bytes.
+ */
+void *memset16(uint16_t *s, uint16_t v, size_t count)
+{
+ uint16_t *xs = s;
+
+ while (count--)
+ *xs++ = v;
+ return s;
+}
+EXPORT_SYMBOL(memset16);
+#endif
+
+#ifndef __HAVE_ARCH_MEMSET32
+/**
+ * memset32() - Fill a memory area with a uint32_t
+ * @s: Pointer to the start of the area.
+ * @v: The value to fill the area with
+ * @count: The number of values to store
+ *
+ * Differs from memset() in that it fills with a uint32_t instead
+ * of a byte. Remember that @count is the number of uint32_ts to
+ * store, not the number of bytes.
+ */
+void *memset32(uint32_t *s, uint32_t v, size_t count)
+{
+ uint32_t *xs = s;
+
+ while (count--)
+ *xs++ = v;
+ return s;
+}
+EXPORT_SYMBOL(memset32);
+#endif
+
+#ifndef __HAVE_ARCH_MEMSET64
+/**
+ * memset64() - Fill a memory area with a uint64_t
+ * @s: Pointer to the start of the area.
+ * @v: The value to fill the area with
+ * @count: The number of values to store
+ *
+ * Differs from memset() in that it fills with a uint64_t instead
+ * of a byte. Remember that @count is the number of uint64_ts to
+ * store, not the number of bytes.
+ */
+void *memset64(uint64_t *s, uint64_t v, size_t count)
+{
+ uint64_t *xs = s;
+
+ while (count--)
+ *xs++ = v;
+ return s;
+}
+EXPORT_SYMBOL(memset64);
+#endif
+
#ifndef __HAVE_ARCH_MEMCPY
/**
* memcpy - Copy one area of memory to another
_
Patches currently in -mm which might be from mawilcox@xxxxxxxxxxxxx are
add-multibyte-memset-functions.patch
add-testcases-for-memset16-32-64.patch
x86-implement-memset16-memset32-memset64.patch
arm-implement-memset32-memset64.patch
alpha-add-support-for-memset16.patch
zram-convert-to-using-memset_l.patch
sym53c8xx_2-convert-to-use-memset32.patch
vga-optimise-console-scrolling.patch
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