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runtime: more flexible heap memory mapping on 64-bits
Fixes golang#5641. R=golang-dev, dave, daniel.morsing, iant CC=golang-dev, kcc https://golang.org/cl/10126044
1 parent dbcfed9 commit a8ad859

3 files changed

Lines changed: 68 additions & 5 deletions

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‎misc/cgo/testasan/main.go‎

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@@ -0,0 +1,49 @@
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// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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/*
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#include <sys/mman.h>
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#include <pthread.h>
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#include <unistd.h>
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void ctor(void) __attribute__((constructor));
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static void* thread(void*);
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void
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ctor(void)
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{
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// occupy memory where Go runtime would normally map heap
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mmap((void*)0x00c000000000, 64<<10, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, -1, 0);
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// allocate 4K every 10us
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pthread_t t;
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pthread_create(&t, 0, thread, 0);
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}
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static void*
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thread(void *p)
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{
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for(;;) {
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usleep(10000);
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mmap(0, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
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}
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return 0;
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}
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*/
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import "C"
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import (
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"time"
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)
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func main() {
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// ensure that we can function normally
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var v [][]byte
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for i := 0; i < 1000; i++ {
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time.Sleep(10 * time.Microsecond)
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v = append(v, make([]byte, 64<<10))
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}
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}

‎src/pkg/runtime/malloc.goc‎

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@@ -303,6 +303,7 @@ runtime·mallocinit(void)
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extern byte end[];
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byte *want;
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uintptr limit;
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uint64 i;
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p = nil;
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arena_size = 0;
@@ -330,15 +331,17 @@ runtime·mallocinit(void)
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// 128 GB (MaxMem) should be big enough for now.
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//
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// The code will work with the reservation at any address, but ask
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// SysReserve to use 0x000000c000000000 if possible.
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// SysReserve to use 0x0000XXc000000000 if possible (XX=00...7f).
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// Allocating a 128 GB region takes away 37 bits, and the amd64
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// doesn't let us choose the top 17 bits, so that leaves the 11 bits
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// in the middle of 0x00c0 for us to choose. Choosing 0x00c0 means
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// that the valid memory addresses will begin 0x00c0, 0x00c1, ..., 0x0x00df.
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// that the valid memory addresses will begin 0x00c0, 0x00c1, ..., 0x00df.
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// In little-endian, that's c0 00, c1 00, ..., df 00. None of those are valid
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// UTF-8 sequences, and they are otherwise as far away from
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// ff (likely a common byte) as possible. An earlier attempt to use 0x11f8
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// caused out of memory errors on OS X during thread allocations.
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// ff (likely a common byte) as possible. If that fails, we try other 0xXXc0
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// addresses. An earlier attempt to use 0x11f8 caused out of memory errors
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// on OS X during thread allocations. 0x00c0 causes conflicts with
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// AddressSanitizer which reserves all memory up to 0x0100.
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// These choices are both for debuggability and to reduce the
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// odds of the conservative garbage collector not collecting memory
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// because some non-pointer block of memory had a bit pattern
@@ -353,7 +356,12 @@ runtime·mallocinit(void)
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spans_size = arena_size / PageSize * sizeof(runtime·mheap.spans[0]);
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// round spans_size to pages
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spans_size = (spans_size + ((1<<PageShift) - 1)) & ~((1<<PageShift) - 1);
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p = runtime·SysReserve((void*)(0x00c0ULL<<32), bitmap_size + spans_size + arena_size);
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for(i = 0; i <= 0x7f; i++) {
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p = (void*)(i<<40 | 0x00c0ULL<<32);
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p = runtime·SysReserve(p, bitmap_size + spans_size + arena_size);
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if(p != nil)
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break;
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}
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}
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if (p == nil) {
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// On a 32-bit machine, we can't typically get away

‎src/run.bash‎

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@@ -108,6 +108,12 @@ esac
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./test.bash
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) || exit $?
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[ "$CGO_ENABLED" != 1 ] ||
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[ "$GOHOSTOS-$GOARCH" != linux-amd64 ] ||
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(xcd ../misc/cgo/testasan
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go run main.go
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) || exit $?
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(xcd ../doc/progs
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time ./run
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) || exit $?

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