From: Wolfgang Wander <wwc@rentec.com>
Ingo recently introduced a great speedup for allocating new mmaps using the
free_area_cache pointer which boosts the specweb SSL benchmark by 4-5% and
causes huge performance increases in thread creation.
The downside of this patch is that it does lead to fragmentation in the
mmap-ed areas (visible via /proc/self/maps), such that some applications
that work fine under 2.4 kernels quickly run out of memory on any 2.6
kernel.
The problem is twofold:
1) the free_area_cache is used to continue a search for memory where
the last search ended. Before the change new areas were always
searched from the base address on.
So now new small areas are cluttering holes of all sizes
throughout the whole mmap-able region whereas before small holes
tended to close holes near the base leaving holes far from the base
large and available for larger requests.
2) the free_area_cache also is set to the location of the last
munmap-ed area so in scenarios where we allocate e.g. five regions of
1K each, then free regions 4 2 3 in this order the next request for 1K
will be placed in the position of the old region 3, whereas before we
appended it to the still active region 1, placing it at the location
of the old region 2. Before we had 1 free region of 2K, now we only
get two free regions of 1K -> fragmentation.
The patch addresses thes issues by introducing yet another cache descriptor
cached_hole_size that contains the largest known hole size below the
current free_area_cache. If a new request comes in the size is compared
against the cached_hole_size and if the request can be filled with a hole
below free_area_cache the search is started from the base instead.
The results look promising: Whereas 2.6.12-rc4 fragments quickly and my
(earlier posted) leakme.c test program terminates after 50000+ iterations
with 96 distinct and fragmented maps in /proc/self/maps it performs nicely
(as expected) with thread creation, Ingo's test_str02 with 20000 threads
requires 0.7s system time.
Taking out Ingo's patch (un-patch available per request) by basically
deleting all mentions of free_area_cache from the kernel and starting the
search for new memory always at the respective bases we observe: leakme
terminates successfully with 11 distinctive hardly fragmented areas in
/proc/self/maps but thread creating is gringdingly slow: 30+s(!) system
time for Ingo's test_str02 with 20000 threads.
Now - drumroll ;-) the appended patch works fine with leakme: it ends with
only 7 distinct areas in /proc/self/maps and also thread creation seems
sufficiently fast with 0.71s for 20000 threads.
Signed-off-by: Wolfgang Wander <wwc@rentec.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
arch/arm/mm/mmap.c | 10 +++++++++-
arch/i386/mm/hugetlbpage.c | 33 ++++++++++++++++++++++++++++-----
arch/ia64/kernel/sys_ia64.c | 13 +++++++++++--
arch/ppc64/mm/hugetlbpage.c | 32 ++++++++++++++++++++++++++++----
arch/sh/kernel/sys_sh.c | 8 ++++++++
arch/sparc64/kernel/sys_sparc.c | 8 ++++++++
arch/x86_64/ia32/ia32_aout.c | 1 +
arch/x86_64/kernel/sys_x86_64.c | 8 ++++++++
fs/binfmt_aout.c | 1 +
fs/binfmt_elf.c | 1 +
fs/hugetlbfs/inode.c | 5 +++++
include/linux/sched.h | 5 +++--
kernel/fork.c | 2 ++
mm/mmap.c | 35 ++++++++++++++++++++++++++++++-----
14 files changed, 143 insertions(+), 19 deletions(-)
diff -puN arch/arm/mm/mmap.c~avoiding-mmap-fragmentation arch/arm/mm/mmap.c
--- 25/arch/arm/mm/mmap.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/arm/mm/mmap.c 2005-05-11 18:03:14.000000000 -0700
@@ -73,7 +73,12 @@ arch_get_unmapped_area(struct file *filp
(!vma || addr + len <= vma->vm_start))
return addr;
}
- start_addr = addr = mm->free_area_cache;
+ if( len > mm->cached_hole_size )
+ start_addr = addr = mm->free_area_cache;
+ else {
+ start_addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
+ }
full_search:
if (do_align)
@@ -90,6 +95,7 @@ full_search:
*/
if (start_addr != TASK_UNMAPPED_BASE) {
start_addr = addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -101,6 +107,8 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
addr = vma->vm_end;
if (do_align)
addr = COLOUR_ALIGN(addr, pgoff);
diff -puN arch/i386/mm/hugetlbpage.c~avoiding-mmap-fragmentation arch/i386/mm/hugetlbpage.c
--- 25/arch/i386/mm/hugetlbpage.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/i386/mm/hugetlbpage.c 2005-05-11 18:03:14.000000000 -0700
@@ -140,7 +140,12 @@ static unsigned long hugetlb_get_unmappe
struct vm_area_struct *vma;
unsigned long start_addr;
- start_addr = mm->free_area_cache;
+ if( len > mm->cached_hole_size )
+ start_addr = mm->free_area_cache;
+ else {
+ start_addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
+ }
full_search:
addr = ALIGN(start_addr, HPAGE_SIZE);
@@ -154,6 +159,7 @@ full_search:
*/
if (start_addr != TASK_UNMAPPED_BASE) {
start_addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -162,6 +168,8 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
addr = ALIGN(vma->vm_end, HPAGE_SIZE);
}
}
@@ -173,12 +181,17 @@ static unsigned long hugetlb_get_unmappe
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma, *prev_vma;
unsigned long base = mm->mmap_base, addr = addr0;
+ unsigned long largest_hole = mm->cached_hole_size;
int first_time = 1;
/* don't allow allocations above current base */
if (mm->free_area_cache > base)
mm->free_area_cache = base;
+ if( len <= largest_hole ) {
+ largest_hole = 0;
+ mm->free_area_cache = base;
+ }
try_again:
/* make sure it can fit in the remaining address space */
if (mm->free_area_cache < len)
@@ -199,13 +212,20 @@ try_again:
* vma->vm_start, use it:
*/
if (addr + len <= vma->vm_start &&
- (!prev_vma || (addr >= prev_vma->vm_end)))
+ (!prev_vma || (addr >= prev_vma->vm_end))) {
/* remember the address as a hint for next time */
- return (mm->free_area_cache = addr);
- else
+ mm->cached_hole_size = largest_hole;
+ return (mm->free_area_cache = addr);
+ } else
/* pull free_area_cache down to the first hole */
- if (mm->free_area_cache == vma->vm_end)
+ if (mm->free_area_cache == vma->vm_end) {
mm->free_area_cache = vma->vm_start;
+ mm->cached_hole_size = largest_hole;
+ }
+
+ /* remember the largest hole we saw so far */
+ if( addr + largest_hole < vma->vm_start )
+ largest_hole = vma->vm_start - addr;
/* try just below the current vma->vm_start */
addr = (vma->vm_start - len) & HPAGE_MASK;
@@ -218,6 +238,7 @@ fail:
*/
if (first_time) {
mm->free_area_cache = base;
+ largest_hole = 0;
first_time = 0;
goto try_again;
}
@@ -228,6 +249,7 @@ fail:
* allocations.
*/
mm->free_area_cache = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = ~0UL;
addr = hugetlb_get_unmapped_area_bottomup(file, addr0,
len, pgoff, flags);
@@ -235,6 +257,7 @@ fail:
* Restore the topdown base:
*/
mm->free_area_cache = base;
+ mm->cached_hole_size = ~0UL;
return addr;
}
diff -puN arch/ia64/kernel/sys_ia64.c~avoiding-mmap-fragmentation arch/ia64/kernel/sys_ia64.c
--- 25/arch/ia64/kernel/sys_ia64.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/ia64/kernel/sys_ia64.c 2005-05-11 18:03:14.000000000 -0700
@@ -38,8 +38,14 @@ arch_get_unmapped_area (struct file *fil
if (REGION_NUMBER(addr) == REGION_HPAGE)
addr = 0;
#endif
- if (!addr)
- addr = mm->free_area_cache;
+ if (!addr) {
+ if( len > mm->cached_hole_size )
+ addr = mm->free_area_cache;
+ else {
+ addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
+ }
+ }
if (map_shared && (TASK_SIZE > 0xfffffffful))
/*
@@ -59,6 +65,7 @@ arch_get_unmapped_area (struct file *fil
if (start_addr != TASK_UNMAPPED_BASE) {
/* Start a new search --- just in case we missed some holes. */
addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -68,6 +75,8 @@ arch_get_unmapped_area (struct file *fil
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
addr = (vma->vm_end + align_mask) & ~align_mask;
}
}
diff -puN arch/ppc64/mm/hugetlbpage.c~avoiding-mmap-fragmentation arch/ppc64/mm/hugetlbpage.c
--- 25/arch/ppc64/mm/hugetlbpage.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/ppc64/mm/hugetlbpage.c 2005-05-11 18:03:14.000000000 -0700
@@ -292,7 +292,12 @@ unsigned long arch_get_unmapped_area(str
&& !is_hugepage_only_range(mm, addr,len))
return addr;
}
- start_addr = addr = mm->free_area_cache;
+ if( len > mm->cached_hole_size )
+ start_addr = addr = mm->free_area_cache;
+ else {
+ start_addr = addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
+ }
full_search:
vma = find_vma(mm, addr);
@@ -316,6 +321,8 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
addr = vma->vm_end;
vma = vma->vm_next;
}
@@ -323,6 +330,7 @@ full_search:
/* Make sure we didn't miss any holes */
if (start_addr != TASK_UNMAPPED_BASE) {
start_addr = addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -344,6 +352,7 @@ arch_get_unmapped_area_topdown(struct fi
struct vm_area_struct *vma, *prev_vma;
struct mm_struct *mm = current->mm;
unsigned long base = mm->mmap_base, addr = addr0;
+ unsigned long largest_hole = mm->cached_hole_size;
int first_time = 1;
/* requested length too big for entire address space */
@@ -364,6 +373,10 @@ arch_get_unmapped_area_topdown(struct fi
return addr;
}
+ if( len <= largest_hole ) {
+ largest_hole = 0;
+ mm->free_area_cache = base;
+ }
try_again:
/* make sure it can fit in the remaining address space */
if (mm->free_area_cache < len)
@@ -392,13 +405,21 @@ hugepage_recheck:
* vma->vm_start, use it:
*/
if (addr+len <= vma->vm_start &&
- (!prev_vma || (addr >= prev_vma->vm_end)))
+ (!prev_vma || (addr >= prev_vma->vm_end))) {
/* remember the address as a hint for next time */
- return (mm->free_area_cache = addr);
+ mm->cached_hole_size = largest_hole;
+ return (mm->free_area_cache = addr);
+ }
else
/* pull free_area_cache down to the first hole */
- if (mm->free_area_cache == vma->vm_end)
+ if (mm->free_area_cache == vma->vm_end) {
mm->free_area_cache = vma->vm_start;
+ mm->cached_hole_size = largest_hole;
+ }
+
+ /* remember the largest hole we saw so far */
+ if( addr + largest_hole < vma->vm_start )
+ largest_hole = vma->vm_start - addr;
/* try just below the current vma->vm_start */
addr = vma->vm_start-len;
@@ -411,6 +432,7 @@ fail:
*/
if (first_time) {
mm->free_area_cache = base;
+ largest_hole = 0;
first_time = 0;
goto try_again;
}
@@ -421,11 +443,13 @@ fail:
* allocations.
*/
mm->free_area_cache = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = ~0UL;
addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
/*
* Restore the topdown base:
*/
mm->free_area_cache = base;
+ mm->cached_hole_size = ~0UL;
return addr;
}
diff -puN arch/sh/kernel/sys_sh.c~avoiding-mmap-fragmentation arch/sh/kernel/sys_sh.c
--- 25/arch/sh/kernel/sys_sh.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/sh/kernel/sys_sh.c 2005-05-11 18:03:14.000000000 -0700
@@ -79,6 +79,10 @@ unsigned long arch_get_unmapped_area(str
(!vma || addr + len <= vma->vm_start))
return addr;
}
+ if( len <= mm->cached_hole_size ) {
+ mm->cached_hole_size = 0;
+ mm->free_area_cache = TASK_UNMAPPED_BASE;
+ }
if (flags & MAP_PRIVATE)
addr = PAGE_ALIGN(mm->free_area_cache);
else
@@ -95,6 +99,7 @@ full_search:
*/
if (start_addr != TASK_UNMAPPED_BASE) {
start_addr = addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -106,6 +111,9 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
+
addr = vma->vm_end;
if (!(flags & MAP_PRIVATE))
addr = COLOUR_ALIGN(addr);
diff -puN arch/sparc64/kernel/sys_sparc.c~avoiding-mmap-fragmentation arch/sparc64/kernel/sys_sparc.c
--- 25/arch/sparc64/kernel/sys_sparc.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/sparc64/kernel/sys_sparc.c 2005-05-11 18:03:14.000000000 -0700
@@ -84,6 +84,10 @@ unsigned long arch_get_unmapped_area(str
return addr;
}
+ if( len <= mm->cached_hole_size ) {
+ mm->cached_hole_size = 0;
+ mm->free_area_cache = TASK_UNMAPPED_BASE;
+ }
start_addr = addr = mm->free_area_cache;
task_size -= len;
@@ -103,6 +107,7 @@ full_search:
if (task_size < addr) {
if (start_addr != TASK_UNMAPPED_BASE) {
start_addr = addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -114,6 +119,9 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
+
addr = vma->vm_end;
if (do_color_align)
addr = COLOUR_ALIGN(addr, pgoff);
diff -puN arch/x86_64/ia32/ia32_aout.c~avoiding-mmap-fragmentation arch/x86_64/ia32/ia32_aout.c
--- 25/arch/x86_64/ia32/ia32_aout.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/x86_64/ia32/ia32_aout.c 2005-05-11 17:52:24.000000000 -0700
@@ -312,6 +312,7 @@ static int load_aout_binary(struct linux
current->mm->brk = ex.a_bss +
(current->mm->start_brk = N_BSSADDR(ex));
current->mm->free_area_cache = TASK_UNMAPPED_BASE;
+ current->mm->cached_hole_size = 0;
set_mm_counter(current->mm, rss, 0);
current->mm->mmap = NULL;
diff -puN arch/x86_64/kernel/sys_x86_64.c~avoiding-mmap-fragmentation arch/x86_64/kernel/sys_x86_64.c
--- 25/arch/x86_64/kernel/sys_x86_64.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/arch/x86_64/kernel/sys_x86_64.c 2005-05-11 18:03:14.000000000 -0700
@@ -111,6 +111,10 @@ arch_get_unmapped_area(struct file *filp
(!vma || addr + len <= vma->vm_start))
return addr;
}
+ if( len <= mm->cached_hole_size ) {
+ mm->cached_hole_size = 0;
+ mm->free_area_cache = begin;
+ }
addr = mm->free_area_cache;
if (addr < begin)
addr = begin;
@@ -126,6 +130,7 @@ full_search:
*/
if (start_addr != begin) {
start_addr = addr = begin;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -137,6 +142,9 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
+
addr = vma->vm_end;
}
}
diff -puN fs/binfmt_aout.c~avoiding-mmap-fragmentation fs/binfmt_aout.c
--- 25/fs/binfmt_aout.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/fs/binfmt_aout.c 2005-05-11 17:52:24.000000000 -0700
@@ -316,6 +316,7 @@ static int load_aout_binary(struct linux
current->mm->brk = ex.a_bss +
(current->mm->start_brk = N_BSSADDR(ex));
current->mm->free_area_cache = current->mm->mmap_base;
+ current->mm->cached_hole_size = current->mm->cached_hole_size;
set_mm_counter(current->mm, rss, 0);
current->mm->mmap = NULL;
diff -puN fs/binfmt_elf.c~avoiding-mmap-fragmentation fs/binfmt_elf.c
--- 25/fs/binfmt_elf.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/fs/binfmt_elf.c 2005-05-11 18:03:14.000000000 -0700
@@ -775,6 +775,7 @@ static int load_elf_binary(struct linux_
change some of these later */
set_mm_counter(current->mm, rss, 0);
current->mm->free_area_cache = current->mm->mmap_base;
+ current->mm->cached_hole_size = current->mm->cached_hole_size;
retval = setup_arg_pages(bprm, randomize_stack_top(STACK_TOP),
executable_stack);
if (retval < 0) {
diff -puN fs/hugetlbfs/inode.c~avoiding-mmap-fragmentation fs/hugetlbfs/inode.c
--- 25/fs/hugetlbfs/inode.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/fs/hugetlbfs/inode.c 2005-05-11 18:03:14.000000000 -0700
@@ -122,6 +122,11 @@ hugetlb_get_unmapped_area(struct file *f
start_addr = mm->free_area_cache;
+ if(len <= mm->cached_hole_size )
+ start_addr = TASK_UNMAPPED_BASE;
+
+
+
full_search:
addr = ALIGN(start_addr, HPAGE_SIZE);
diff -puN include/linux/sched.h~avoiding-mmap-fragmentation include/linux/sched.h
--- 25/include/linux/sched.h~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/include/linux/sched.h 2005-05-11 17:52:24.000000000 -0700
@@ -219,8 +219,9 @@ struct mm_struct {
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags);
void (*unmap_area) (struct vm_area_struct *area);
- unsigned long mmap_base; /* base of mmap area */
- unsigned long free_area_cache; /* first hole */
+ unsigned long mmap_base; /* base of mmap area */
+ unsigned long cached_hole_size; /* if non-zero, the largest hole below free_area_cache */
+ unsigned long free_area_cache; /* first hole of size cached_hole_size or larger */
pgd_t * pgd;
atomic_t mm_users; /* How many users with user space? */
atomic_t mm_count; /* How many references to "struct mm_struct" (users count as 1) */
diff -puN kernel/fork.c~avoiding-mmap-fragmentation kernel/fork.c
--- 25/kernel/fork.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/kernel/fork.c 2005-05-11 17:52:24.000000000 -0700
@@ -194,6 +194,7 @@ static inline int dup_mmap(struct mm_str
mm->mmap = NULL;
mm->mmap_cache = NULL;
mm->free_area_cache = oldmm->mmap_base;
+ mm->cached_hole_size = ~0UL;
mm->map_count = 0;
set_mm_counter(mm, rss, 0);
set_mm_counter(mm, anon_rss, 0);
@@ -322,6 +323,7 @@ static struct mm_struct * mm_init(struct
mm->ioctx_list = NULL;
mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm);
mm->free_area_cache = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = ~0UL;
if (likely(!mm_alloc_pgd(mm))) {
mm->def_flags = 0;
diff -puN mm/mmap.c~avoiding-mmap-fragmentation mm/mmap.c
--- 25/mm/mmap.c~avoiding-mmap-fragmentation 2005-05-11 17:52:24.000000000 -0700
+++ 25-akpm/mm/mmap.c 2005-05-11 18:03:14.000000000 -0700
@@ -1175,7 +1175,12 @@ arch_get_unmapped_area(struct file *filp
(!vma || addr + len <= vma->vm_start))
return addr;
}
- start_addr = addr = mm->free_area_cache;
+ if( len > mm->cached_hole_size )
+ start_addr = addr = mm->free_area_cache;
+ else {
+ start_addr = addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
+ }
full_search:
for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
@@ -1186,7 +1191,8 @@ full_search:
* some holes.
*/
if (start_addr != TASK_UNMAPPED_BASE) {
- start_addr = addr = TASK_UNMAPPED_BASE;
+ start_addr = addr = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -1198,6 +1204,8 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
addr = vma->vm_end;
}
}
@@ -1209,8 +1217,13 @@ void arch_unmap_area(struct vm_area_stru
* Is this a new hole at the lowest possible address?
*/
if (area->vm_start >= TASK_UNMAPPED_BASE &&
- area->vm_start < area->vm_mm->free_area_cache)
- area->vm_mm->free_area_cache = area->vm_start;
+ area->vm_start < area->vm_mm->free_area_cache) {
+ unsigned area_size = area->vm_end-area->vm_start;
+ if( area->vm_mm->cached_hole_size < area_size )
+ area->vm_mm->cached_hole_size = area_size;
+ else
+ area->vm_mm->cached_hole_size = ~0UL;
+ }
}
/*
@@ -1240,6 +1253,12 @@ arch_get_unmapped_area_topdown(struct fi
return addr;
}
+ /* check if free_area_cache is useful for us */
+ if( len <= mm->cached_hole_size ) {
+ mm->cached_hole_size = 0;
+ mm->free_area_cache = mm->mmap_base;
+ }
+
/* either no address requested or can't fit in requested address hole */
addr = mm->free_area_cache;
@@ -1264,6 +1283,10 @@ arch_get_unmapped_area_topdown(struct fi
/* remember the address as a hint for next time */
return (mm->free_area_cache = addr);
+ /* remember the largest hole we saw so far */
+ if( addr + mm->cached_hole_size < vma->vm_start )
+ mm->cached_hole_size = vma->vm_start - addr;
+
/* try just below the current vma->vm_start */
addr = vma->vm_start-len;
} while (len <= vma->vm_start);
@@ -1274,12 +1297,14 @@ arch_get_unmapped_area_topdown(struct fi
* can happen with large stack limits and large mmap()
* allocations.
*/
- mm->free_area_cache = TASK_UNMAPPED_BASE;
+ mm->cached_hole_size = ~0UL;
+ mm->free_area_cache = TASK_UNMAPPED_BASE;
addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
/*
* Restore the topdown base:
*/
mm->free_area_cache = mm->mmap_base;
+ mm->cached_hole_size = ~0UL;
return addr;
}
_