runtime: madvise and SysUnused for Linux

SysUnused being a direct call to madvise MADV_DONTNEED.

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/5477057

src/pkg/runtime/linux/386/defs.h

@@ -12,6 +12,8 @@ enum {
 	MAP_PRIVATE	= 0x2,
 	MAP_FIXED	= 0x10,
 
+	MADV_DONTNEED	= 0x4,
+
 	SA_RESTART	= 0x10000000,
 	SA_ONSTACK	= 0x8000000,
 	SA_RESTORER	= 0x4000000,

src/pkg/runtime/linux/386/sys.s

@@ -212,6 +212,17 @@ TEXT runtime·munmap(SB),7,$0
 	INT $3
 	RET
 
+TEXT runtime·madvise(SB),7,$0
+	MOVL	$219, AX	// madvise
+	MOVL	4(SP), BX
+	MOVL	8(SP), CX
+	MOVL	12(SP), DX
+	CALL	*runtime·_vdso(SB)
+	CMPL	AX, $0xfffff001
+	JLS	2(PC)
+	INT $3
+	RET
+
 // int32 futex(int32 *uaddr, int32 op, int32 val,
 //	struct timespec *timeout, int32 *uaddr2, int32 val2);
 TEXT runtime·futex(SB),7,$0

src/pkg/runtime/linux/amd64/defs.h

@@ -12,6 +12,8 @@ enum {
 	MAP_PRIVATE	= 0x2,
 	MAP_FIXED	= 0x10,
 
+	MADV_DONTNEED	= 0x4,
+
 	SA_RESTART	= 0x10000000,
 	SA_ONSTACK	= 0x8000000,
 	SA_RESTORER	= 0x4000000,
@@ -95,7 +97,7 @@ struct Siginfo {
 	int32	si_signo;
 	int32	si_errno;
 	int32	si_code;
-	byte	Pad_godefs_0[4];
+	byte	Pad_cgo_0[4];
 	byte	_sifields[112];
 };
 struct Itimerval {
@@ -181,7 +183,7 @@ struct Fpreg1 {
 struct Sigaltstack {
 	byte	*ss_sp;
 	int32	ss_flags;
-	byte	Pad_godefs_0[4];
+	byte	Pad_cgo_0[4];
 	uint64	ss_size;
 };
 struct Mcontext {

src/pkg/runtime/linux/amd64/sys.s

@@ -192,6 +192,17 @@ TEXT runtime·munmap(SB),7,$0
 	CALL	runtime·notok(SB)
 	RET
 
+TEXT runtime·madvise(SB),7,$0
+	MOVQ	8(SP), DI
+	MOVQ	16(SP), SI
+	MOVQ	24(SP), DX
+	MOVQ	$28, AX	// madvise
+	SYSCALL
+	CMPQ	AX, $0xfffffffffffff001
+	JLS	2(PC)
+	CALL	runtime·notok(SB)
+	RET
+
 TEXT runtime·notok(SB),7,$0
 	MOVQ	$0xf1, BP
 	MOVQ	BP, (BP)

src/pkg/runtime/linux/arm/defs.h

@@ -11,6 +11,7 @@ enum {
 	MAP_ANON = 0x20,
 	MAP_PRIVATE = 0x2,
 	MAP_FIXED = 0x10,
+	MADV_DONTNEED = 0x4,
 	SA_RESTART = 0x10000000,
 	SA_ONSTACK = 0x8000000,
 	SA_RESTORER = 0x4000000,

src/pkg/runtime/linux/arm/sys.s

@@ -28,6 +28,7 @@
 #define SYS_futex (SYS_BASE + 240)
 #define SYS_exit_group (SYS_BASE + 248)
 #define SYS_munmap (SYS_BASE + 91)
+#define SYS_madvise (SYS_BASE + 220)
 #define SYS_setitimer (SYS_BASE + 104)
 #define SYS_mincore (SYS_BASE + 219)
 #define SYS_gettid (SYS_BASE + 224)
@@ -111,6 +112,14 @@ TEXT runtime·munmap(SB),7,$0
 	SWI	$0
 	RET
 
+TEXT runtime·madvise(SB),7,$0
+	MOVW	0(FP), R0
+	MOVW	4(FP), R1
+	MOVW	8(FP), R2
+	MOVW	$SYS_madvise, R7
+	SWI	$0
+	RET
+
 TEXT runtime·setitimer(SB),7,$0
 	MOVW	0(FP), R0
 	MOVW	4(FP), R1

src/pkg/runtime/linux/defs.go

@@ -36,6 +36,8 @@ const (
 	MAP_PRIVATE = C.MAP_PRIVATE
 	MAP_FIXED   = C.MAP_FIXED
 
+	MADV_DONTNEED = C.MADV_DONTNEED
+
 	SA_RESTART  = C.SA_RESTART
 	SA_ONSTACK  = C.SA_ONSTACK
 	SA_RESTORER = C.SA_RESTORER

src/pkg/runtime/linux/defs2.go

@@ -17,6 +17,7 @@ package runtime
 /*
 #cgo CFLAGS: -I/home/rsc/pub/linux-2.6/arch/x86/include -I/home/rsc/pub/linux-2.6/include -D_LOOSE_KERNEL_NAMES -D__ARCH_SI_UID_T=__kernel_uid32_t
 
+#define size_t __kernel_size_t
 #include <asm/signal.h>
 #include <asm/mman.h>
 #include <asm/sigcontext.h>
@@ -47,6 +48,8 @@ const (
 	MAP_PRIVATE = C.MAP_PRIVATE
 	MAP_FIXED   = C.MAP_FIXED
 
+	MADV_DONTNEED = C.MADV_DONTNEED
+
 	SA_RESTART  = C.SA_RESTART
 	SA_ONSTACK  = C.SA_ONSTACK
 	SA_RESTORER = C.SA_RESTORER

src/pkg/runtime/linux/defs_arm.go

@@ -53,6 +53,8 @@ const (
 	MAP_PRIVATE = C.MAP_PRIVATE
 	MAP_FIXED   = C.MAP_FIXED
 
+	MADV_DONTNEED = C.MADV_DONTNEED
+
 	SA_RESTART  = C.SA_RESTART
 	SA_ONSTACK  = C.SA_ONSTACK
 	SA_RESTORER = C.SA_RESTORER

src/pkg/runtime/linux/mem.c

@@ -56,9 +56,7 @@ runtime·SysAlloc(uintptr n)
 void
 runtime·SysUnused(void *v, uintptr n)
 {
-	USED(v);
-	USED(n);
-	// TODO(rsc): call madvise MADV_DONTNEED
+	runtime·madvise(v, n, MADV_DONTNEED);
 }
 
 void