Re: [PATCH] lazy freeing of memory through MADV_FREE

Jakub Jelinek
2007-04-21T07:12:12Z

On Fri, Apr 20, 2007 at 07:52:44PM -0400, Rik van Riel wrote:
> It turns out that Nick's patch does not improve peak
> performance much, but it does prevent the decline when
> running with 16 threads on my quad core CPU!
>
> We _definately_ want both patches, there's a huge benefit
> in having them both.
>
> Here are the transactions/seconds for each combination:
>
> vanilla new glibc madv_free kernel madv_free + mmap_sem
> threads
>
> 1 610 609 596 545
> 2 1032 1136 1196 1200
> 4 1070 1128 2014 2024
> 8 1000 1088 1665 2087
> 16 779 1073 1310 1999

FYI, I have uploaded a testing glibc that uses MADV_FREE and falls back
to MADV_DONTUSE if MADV_FREE is not available, to
http://people.redhat.com/jakub/glibc/2.5.90-21.1/
and I'm also attaching the glibc patch for those who want to build it
themselves:

2007-04-19 Ulrich Drepper <drepper@redhat.com>
Jakub Jelinek <jakub@redhat.com>

* malloc/arena.c (heap_info): Add mprotect_size field, adjust pad.
(new_heap): Initialize mprotect_size.
(no_madv_free): New variable.
(grow_heap): When growing, only mprotect from mprotect_size till
new_size if mprotect_size is smaller. When shrinking, use PROT_NONE
MMAP for __libc_enable_secure only, otherwise if MADV_FREE is
available use it and fall back to MADV_DONTNEED.
* sysdeps/unix/sysv/linux/alpha/bits/mman.h (MADV_FREE): Define.
* sysdeps/unix/sysv/linux/ia64/bits/mman.h (MADV_FREE): Likewise.
* sysdeps/unix/sysv/linux/i386/bits/mman.h (MADV_FREE): Likewise.
* sysdeps/unix/sysv/linux/s390/bits/mman.h (MADV_FREE): Likewise.
* sysdeps/unix/sysv/linux/powerpc/bits/mman.h (MADV_FREE): Likewise.
* sysdeps/unix/sysv/linux/x86_64/bits/mman.h (MADV_FREE): Likewise.
* sysdeps/unix/sysv/linux/sparc/bits/mman.h (MADV_FREE): Likewise.
* sysdeps/unix/sysv/linux/sh/bits/mman.h (MADV_FREE): Likewise.

--- libc/malloc/arena.c.jj 2006-10-31 23:05:31.000000000 +0100
+++ libc/malloc/arena.c 2007-04-19 18:54:20.000000000 +0200
@@ -1,5 +1,6 @@
/* Malloc implementation for multiple threads without lock contention.
- Copyright (C) 2001,2002,2003,2004,2005,2006 Free Software Foundation, Inc.
+ Copyright (C) 2001,2002,2003,2004,2005,2006,2007
+ Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Wolfram Gloger <wg@malloc.de>, 2001.

@@ -59,10 +60,12 @@ typedef struct _heap_info {
mstate ar_ptr; /* Arena for this heap. */
struct _heap_info *prev; /* Previous heap. */
size_t size; /* Current size in bytes. */
+ size_t mprotect_size; /* Size in bytes that has been mprotected
+ PROT_READ|PROT_WRITE. */
/* Make sure the following data is properly aligned, particularly
that sizeof (heap_info) + 2 * SIZE_SZ is a multiple of
- MALLOG_ALIGNMENT. */
- char pad[-5 * SIZE_SZ & MALLOC_ALIGN_MASK];
+ MALLOC_ALIGNMENT. */
+ char pad[-6 * SIZE_SZ & MALLOC_ALIGN_MASK];
} heap_info;

/* Get a compile-time error if the heap_info padding is not correct
@@ -692,10 +695,15 @@ new_heap(size, top_pad) size_t size, top
}
h = (heap_info *)p2;
h->size = size;
+ h->mprotect_size = size;
THREAD_STAT(stat_n_heaps++);
return h;
}

+#if defined _LIBC && defined MADV_FREE
+static int no_madv_free;
+#endif
+
/* Grow or shrink a heap. size is automatically rounded up to a
multiple of the page size if it is positive. */

@@ -714,17 +722,49 @@ grow_heap(h, diff) heap_info *h; long di
new_size = (long)h->size + diff;
if((unsigned long) new_size > (unsigned long) HEAP_MAX_SIZE)
return -1;
- if(mprotect((char *)h + h->size, diff, PROT_READ|PROT_WRITE) != 0)
- return -2;
+ if((unsigned long) new_size > h->mprotect_size) {
+ if (mprotect((char *)h + h->mprotect_size,
+ (unsigned long) new_size - h->mprotect_size,
+ PROT_READ|PROT_WRITE) != 0)
+ return -2;
+ h->mprotect_size = new_size;
+ }
} else {
new_size = (long)h->size + diff;
if(new_size < (long)sizeof(*h))
return -1;
/* Try to re-map the extra heap space freshly to save memory, and
make it inaccessible. */
- if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
- MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
- return -2;
+#ifdef _LIBC
+ if (__builtin_expect (__libc_enable_secure, 0))
+#else
+ if (1)
+#endif
+ {
+ if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
+ MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
+ return -2;
+ h->mprotect_size = new_size;
+ }
+#ifdef _LIBC
+ else
+ {
+# ifdef MADV_FREE
+ if (!__builtin_expect (no_madv_free, 0))
+ {
+ if (__builtin_expect (madvise ((char *)h + new_size,
+ -diff, MADV_FREE), 0) == -1
+ && errno == EINVAL)
+ {
+ no_madv_free = 1;
+ madvise ((char *)h + new_size, -diff, MADV_DONTNEED);
+ }
+ }
+ else
+# endif
+ madvise ((char *)h + new_size, -diff, MADV_DONTNEED);
+ }
+#endif
/*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
}
h->size = new_size;
--- libc/sysdeps/unix/sysv/linux/alpha/bits/mman.h.jj 2006-05-02 16:33:44.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/alpha/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,6 @@
/* Definitions for POSIX memory map interface. Linux/Alpha version.
- Copyright (C) 1997, 1998, 2000, 2003, 2006 Free Software Foundation, Inc.
+ Copyright (C) 1997, 1998, 2000, 2003, 2006, 2007
+ 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
@@ -96,6 +97,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 6 /* Don't need these pages. */
+# define MADV_FREE 7 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */
--- libc/sysdeps/unix/sysv/linux/ia64/bits/mman.h.jj 2006-05-02 16:33:44.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/ia64/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,6 @@
/* Definitions for POSIX memory map interface. Linux/ia64 version.
- Copyright (C) 1997,1998,2000,2003,2005,2006 Free Software Foundation, Inc.
+ Copyright (C) 1997,1998,2000,2003,2005,2006,2007
+ 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
@@ -89,6 +90,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 4 /* Don't need these pages. */
+# define MADV_FREE 5 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */
--- libc/sysdeps/unix/sysv/linux/i386/bits/mman.h.jj 2006-05-02 16:33:44.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/i386/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,6 @@
/* Definitions for POSIX memory map interface. Linux/i386 version.
- Copyright (C) 1997, 2000, 2003, 2005, 2006 Free Software Foundation, Inc.
+ Copyright (C) 1997, 2000, 2003, 2005, 2006, 2007
+ 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
@@ -88,6 +89,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 4 /* Don't need these pages. */
+# define MADV_FREE 5 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */
--- libc/sysdeps/unix/sysv/linux/s390/bits/mman.h.jj 2006-05-02 16:33:44.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/s390/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,6 @@
/* Definitions for POSIX memory map interface. Linux/s390 version.
- Copyright (C) 2000,2001,2002,2003,2005,2006 Free Software Foundation, Inc.
+ Copyright (C) 2000,2001,2002,2003,2005,2006,2007
+ 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
@@ -89,6 +90,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 4 /* Don't need these pages. */
+# define MADV_FREE 5 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */
--- libc/sysdeps/unix/sysv/linux/powerpc/bits/mman.h.jj 2006-05-02 16:33:44.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/powerpc/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,6 @@
/* Definitions for POSIX memory map interface. Linux/PowerPC version.
- Copyright (C) 1997, 2000, 2003, 2005, 2006 Free Software Foundation, Inc.
+ Copyright (C) 1997, 2000, 2003, 2005, 2006, 2007
+ 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
@@ -89,6 +90,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 4 /* Don't need these pages. */
+# define MADV_FREE 5 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */
--- libc/sysdeps/unix/sysv/linux/x86_64/bits/mman.h.jj 2006-05-02 16:33:46.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/x86_64/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,5 @@
/* Definitions for POSIX memory map interface. Linux/x86_64 version.
- Copyright (C) 2001, 2003, 2005, 2006 Free Software Foundation, Inc.
+ Copyright (C) 2001, 2003, 2005, 2006, 2007 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
@@ -89,6 +89,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 4 /* Don't need these pages. */
+# define MADV_FREE 5 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */
--- libc/sysdeps/unix/sysv/linux/sparc/bits/mman.h.jj 2006-05-02 16:33:44.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/sparc/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,6 @@
/* Definitions for POSIX memory map interface. Linux/SPARC version.
- Copyright (C) 1997,1999,2000,2003,2005,2006 Free Software Foundation, Inc.
+ Copyright (C) 1997,1999,2000,2003,2005,2006,2007
+ 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
@@ -90,7 +91,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 4 /* Don't need these pages. */
-# define MADV_FREE 5 /* Content can be freed (Solaris). */
+# define MADV_FREE 5 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */
--- libc/sysdeps/unix/sysv/linux/sh/bits/mman.h.jj 2006-05-02 16:33:44.000000000 +0200
+++ libc/sysdeps/unix/sysv/linux/sh/bits/mman.h 2007-04-19 18:37:43.000000000 +0200
@@ -1,5 +1,6 @@
/* Definitions for POSIX memory map interface. Linux/SH version.
- Copyright (C) 1997,1999,2000,2003,2005,2006 Free Software Foundation, Inc.
+ Copyright (C) 1997,1999,2000,2003,2005,2006,2007
+ 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
@@ -88,6 +89,7 @@
# define MADV_SEQUENTIAL 2 /* Expect sequential page references. */
# define MADV_WILLNEED 3 /* Will need these pages. */
# define MADV_DONTNEED 4 /* Don't need these pages. */
+# define MADV_FREE 5 /* Content can be freed. */
# define MADV_REMOVE 9 /* Remove these pages and resources. */
# define MADV_DONTFORK 10 /* Do not inherit across fork. */
# define MADV_DOFORK 11 /* Do inherit across fork. */

Jakub