arm mmap improvements
Philip Blundell
Philip.Blundell@pobox.com
Sun Sep 14 17:44:00 GMT 2003
This patch contains a couple of performance improvements for mmap() and
mmap64() on arm.
p.
-------------- next part --------------
2003-09-14 Philip Blundell <philb@gnu.org>
* sysdeps/unix/sysv/linux/arm/mmap.S: Use sys_mmap2 if it's known
to be available.
* sysdeps/unix/sysv/linux/arm/mmap2.S: Optimise code a little.
Index: sysdeps/unix/sysv/linux/arm/mmap.S
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/unix/sysv/linux/arm/mmap.S,v
retrieving revision 1.5
diff -u -r1.5 mmap.S
--- sysdeps/unix/sysv/linux/arm/mmap.S 6 Jul 2001 04:56:13 -0000 1.5
+++ sysdeps/unix/sysv/linux/arm/mmap.S 14 Sep 2003 17:18:27 -0000
@@ -1,4 +1,4 @@
-/* Copyright (C) 1998, 2000 Free Software Foundation, Inc.
+/* Copyright (C) 1998, 2000, 2003 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -17,11 +17,47 @@
02111-1307 USA. */
#include <sysdep.h>
+#include <kernel-features.h>
+
+#define EINVAL 22
.text
ENTRY (__mmap)
+# ifdef __ASSUME_MMAP2_SYSCALL
+ /* This code is actually a couple of cycles slower than the
+ sys_mmap version below, so it might seem like a loss. But the
+ code path inside the kernel is sufficiently much shorter to
+ make it a net gain to use mmap2 when it's known to be
+ available. */
+
+ /* shuffle args */
+ str r5, [sp, #-4]!
+ ldr r5, [sp, #8]
+ str r4, [sp, #-4]!
+ ldr r4, [sp, #8]
+
+ /* convert offset to pages */
+ movs ip, r5, lsl #20
+ bne .Linval
+ mov r5, r5, lsr #12
+
+ /* do the syscall */
+ swi SYS_ify (mmap2)
+
+ /* restore registers */
+2:
+ ldr r4, [sp], #4
+ ldr r5, [sp], #4
+
+ cmn r0, $4096
+ RETINSTR(movcc, pc, lr)
+ b PLTJMP(syscall_error)
+.Linval:
+ mov r0, #-EINVAL
+ b 2b
+# else
/* Because we can only get five args through the syscall interface, and
mmap() takes six, we need to build a parameter block and pass its
address instead. The 386 port does a similar trick. */
@@ -49,6 +85,7 @@
cmn r0, $4096
RETINSTR(movcc, pc, lr)
b PLTJMP(syscall_error);
+#endif
PSEUDO_END (__mmap)
Index: sysdeps/unix/sysv/linux/arm/mmap64.S
===================================================================
RCS file: /cvs/glibc/libc/sysdeps/unix/sysv/linux/arm/mmap64.S,v
retrieving revision 1.5
diff -u -r1.5 mmap64.S
--- sysdeps/unix/sysv/linux/arm/mmap64.S 27 Mar 2003 02:45:46 -0000 1.5
+++ sysdeps/unix/sysv/linux/arm/mmap64.S 14 Sep 2003 17:18:27 -0000
@@ -27,38 +27,44 @@
.text
ENTRY (__mmap64)
#ifdef __NR_mmap2
- stmfd sp!, {r4, r5, lr}
- ldr r5, [sp, $16]
- ldr r4, [sp, $12]
- movs ip, r5, lsl $20 @ check that offset is page-aligned
+ ldr ip, [sp, $4] @ offset low part
+ str r5, [sp, #-4]!
+ ldr r5, [sp, $12] @ offset high part
+ str r4, [sp, #-4]!
+ movs r4, ip, lsl $20 @ check that offset is page-aligned
+ mov ip, ip, lsr $12
+ moveqs r4, r5, lsr $12 @ check for overflow
bne .Linval
- ldr ip, [sp, $20]
- mov r5, r5, lsr $12
- orr r5, r5, ip, lsl $20 @ compose page offset
- movs ip, ip, lsr $12
- bne .Linval @ check for overflow
+ ldr r4, [sp, $8] @ load fd
+ orr r5, ip, r5, lsl $20 @ compose page offset
mov ip, r0
swi SYS_ify (mmap2)
cmn r0, $4096
- LOADREGS(ccfd, sp!, {r4, r5, pc})
# ifdef __ASSUME_MMAP2_SYSCALL
- ldmfd sp!, {r4, r5, lr}
+ ldr r4, [sp], #4
+ ldr r5, [sp], #4
+ RETINSTR(movcc, pc, lr)
b PLTJMP(syscall_error)
# else
+ ldrcc r4, [sp], #4
+ ldrcc r5, [sp], #4
+ RETINSTR(movcc, pc, lr)
cmn r0, $ENOSYS
- ldmnefd sp!, {r4, r5, lr}
- bne PLTJMP(syscall_error)
+ bne .Lerror
/* The current kernel does not support mmap2. Fall back to plain
mmap if the offset is small enough. */
- ldr r5, [sp, $20]
+ ldr r5, [sp, $16]
mov r0, ip @ first arg was clobbered
teq r5, $0
- ldmeqfd sp!, {r4, r5, lr}
+ ldreq r4, [sp], #4
+ ldreq r5, [sp], #4
beq PLTJMP(__mmap)
# endif
.Linval:
mov r0, $-EINVAL
- ldmfd sp!, {r4, r5, lr}
+.Lerror:
+ ldr r4, [sp], #4
+ ldr r5, [sp], #4
b PLTJMP(syscall_error)
#else
/* The kernel headers do not support mmap2. Fall back to plain
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