Looking at strcache, I see two other glitches: the size of the cache is
not really aligned with page size: typical malloc implementations
require two size_t entries overhead per allocated area. Also, there is
a one-off computing the overhead size of the strcache struct.
The patch below should correct these issues. Detailed review is
appreciated.
Thanks,
Ralf
2011-01-09 Ralf Wildenhues <ralf.wildenh...@gmx.de>
* strcache.c (STRCACHE_HEADER_SIZE): New define, with fixed
size.
(CACHE_BUFFER_SIZE): Define in terms of STRCACHE_HEADER_SIZE,
and leave two size_t for malloc overhead.
(new_cache, add_string): Adjust sizes.
Index: strcache.c
===================================================================
RCS file: /cvsroot/make/make/strcache.c,v
retrieving revision 2.9
diff -u -r2.9 strcache.c
--- strcache.c 13 Jul 2010 01:20:43 -0000 2.9
+++ strcache.c 9 Jan 2011 07:55:51 -0000
@@ -1,5 +1,5 @@
/* Constant string caching for GNU Make.
-Copyright (C) 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
This file is part of GNU Make.
GNU Make is free software; you can redistribute it and/or modify it under the
@@ -20,10 +20,6 @@
#include "hash.h"
-/* The size (in bytes) of each cache buffer.
- Try to pick something that will map well into the heap. */
-#define CACHE_BUFFER_SIZE (8192 - 16)
-
/* A string cached here will never be freed, so we don't need to worry about
reference counting. We just store the string, and then remember it in a
@@ -34,9 +30,18 @@
char *end; /* Pointer to the beginning of the free space. */
int count; /* # of strings in this buffer (for stats). */
int bytesfree; /* The amount of the buffer that is free. */
- char buffer[1]; /* The buffer comes after this. */
+ char buffer[1]; /* The buffer starts here. */
};
+/* The size of the strcache struct overhead. */
+#define STRCACHE_HEADER_SIZE (sizeof (struct strcache) - 1)
+
+/* The size (in bytes) of each cache buffer.
+ Try to pick something that will map well into the heap:
+ typical malloc implementations require storing 2 size_t per block. */
+#define CACHE_BUFFER_SIZE (8192 - STRCACHE_HEADER_SIZE - 2 * sizeof(size_t))
+
+
static int bufsize = CACHE_BUFFER_SIZE;
static struct strcache *strcache = NULL;
@@ -49,7 +54,7 @@
new_cache()
{
struct strcache *new;
- new = xmalloc (sizeof (*new) + bufsize);
+ new = xmalloc (STRCACHE_HEADER_SIZE + bufsize);
new->end = new->buffer;
new->count = 0;
new->bytesfree = bufsize;
@@ -70,7 +75,7 @@
/* If the string we want is too large to fit into a single buffer, then
we're screwed; nothing will ever fit! Change the maximum size of the
cache to be big enough. */
- if (len > bufsize)
+ if (len + 1 > bufsize)
bufsize = len * 2;
/* First, find a cache with enough free space. We always look through all
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