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authorWolfgang Wander <wwc@rentec.com>2005-06-21 17:14:49 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-21 18:46:16 -0700
commit1363c3cd8603a913a27e2995dccbd70d5312d8e6 (patch)
tree405e7fc1ef44678f3ca0a54c536d0457e6e80f45 /arch
parente7c8d5c9955a4d2e88e36b640563f5d6d5aba48a (diff)
[PATCH] Avoiding mmap fragmentation
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> Credit-to: "Richard Purdie" <rpurdie@rpsys.net> Signed-off-by: Ken Chen <kenneth.w.chen@intel.com> Acked-by: Ingo Molnar <mingo@elte.hu> (partly) Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/mm/mmap.c10
-rw-r--r--arch/i386/mm/hugetlbpage.c34
-rw-r--r--arch/ppc64/mm/hugetlbpage.c34
-rw-r--r--arch/sh/kernel/sys_sh.c8
-rw-r--r--arch/sparc64/kernel/sys_sparc.c8
-rw-r--r--arch/x86_64/ia32/ia32_aout.c1
-rw-r--r--arch/x86_64/kernel/sys_x86_64.c9
7 files changed, 93 insertions, 11 deletions
diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
index 32c4b0e35b3..3de7f84b53c 100644
--- a/arch/arm/mm/mmap.c
+++ b/arch/arm/mm/mmap.c
@@ -73,7 +73,12 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
(!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:
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 --git a/arch/i386/mm/hugetlbpage.c b/arch/i386/mm/hugetlbpage.c
index 5aa06001a4b..3b099f32b94 100644
--- a/arch/i386/mm/hugetlbpage.c
+++ b/arch/i386/mm/hugetlbpage.c
@@ -140,7 +140,12 @@ static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
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_unmapped_area_topdown(struct file *file,
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 +212,21 @@ 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 +239,7 @@ fail:
*/
if (first_time) {
mm->free_area_cache = base;
+ largest_hole = 0;
first_time = 0;
goto try_again;
}
@@ -228,6 +250,7 @@ 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 +258,7 @@ fail:
* Restore the topdown base:
*/
mm->free_area_cache = base;
+ mm->cached_hole_size = ~0UL;
return addr;
}
diff --git a/arch/ppc64/mm/hugetlbpage.c b/arch/ppc64/mm/hugetlbpage.c
index b4ab766f598..fdcfe97c75c 100644
--- a/arch/ppc64/mm/hugetlbpage.c
+++ b/arch/ppc64/mm/hugetlbpage.c
@@ -292,7 +292,12 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
&& !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 file *filp, const unsigned long addr0,
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 file *filp, const unsigned long addr0,
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);
- 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;
@@ -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 --git a/arch/sh/kernel/sys_sh.c b/arch/sh/kernel/sys_sh.c
index df5ac294c37..917b2f32f26 100644
--- a/arch/sh/kernel/sys_sh.c
+++ b/arch/sh/kernel/sys_sh.c
@@ -79,6 +79,10 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
(!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 --git a/arch/sparc64/kernel/sys_sparc.c b/arch/sparc64/kernel/sys_sparc.c
index 0077f02f4b3..5f8c822a2b4 100644
--- a/arch/sparc64/kernel/sys_sparc.c
+++ b/arch/sparc64/kernel/sys_sparc.c
@@ -84,6 +84,10 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
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 --git a/arch/x86_64/ia32/ia32_aout.c b/arch/x86_64/ia32/ia32_aout.c
index 1965efc974d..c12edf5d97f 100644
--- a/arch/x86_64/ia32/ia32_aout.c
+++ b/arch/x86_64/ia32/ia32_aout.c
@@ -312,6 +312,7 @@ static int load_aout_binary(struct linux_binprm * bprm, struct pt_regs * regs)
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 --git a/arch/x86_64/kernel/sys_x86_64.c b/arch/x86_64/kernel/sys_x86_64.c
index d9798dd433f..cc7821c6885 100644
--- a/arch/x86_64/kernel/sys_x86_64.c
+++ b/arch/x86_64/kernel/sys_x86_64.c
@@ -105,6 +105,11 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
(!vma || addr + len <= vma->vm_start))
return addr;
}
+ if (((flags & MAP_32BIT) || test_thread_flag(TIF_IA32))
+ && 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;
@@ -120,6 +125,7 @@ full_search:
*/
if (start_addr != begin) {
start_addr = addr = begin;
+ mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
@@ -131,6 +137,9 @@ 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;
}
}