linux/arch/sh/kernel/sys_sh.c
Wolfgang Wander 1363c3cd86 [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>
2005-06-21 18:46:16 -07:00

298 lines
6.9 KiB
C

/*
* linux/arch/sh/kernel/sys_sh.c
*
* This file contains various random system calls that
* have a non-standard calling sequence on the Linux/SuperH
* platform.
*
* Taken from i386 version.
*/
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/sem.h>
#include <linux/msg.h>
#include <linux/shm.h>
#include <linux/stat.h>
#include <linux/syscalls.h>
#include <linux/mman.h>
#include <linux/file.h>
#include <linux/utsname.h>
#include <asm/uaccess.h>
#include <asm/ipc.h>
/*
* sys_pipe() is the normal C calling standard for creating
* a pipe. It's not the way Unix traditionally does this, though.
*/
asmlinkage int sys_pipe(unsigned long r4, unsigned long r5,
unsigned long r6, unsigned long r7,
struct pt_regs regs)
{
int fd[2];
int error;
error = do_pipe(fd);
if (!error) {
regs.regs[1] = fd[1];
return fd[0];
}
return error;
}
#if defined(HAVE_ARCH_UNMAPPED_AREA)
/*
* To avoid cache alias, we map the shard page with same color.
*/
#define COLOUR_ALIGN(addr) (((addr)+SHMLBA-1)&~(SHMLBA-1))
unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff, unsigned long flags)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long start_addr;
if (flags & MAP_FIXED) {
/* We do not accept a shared mapping if it would violate
* cache aliasing constraints.
*/
if ((flags & MAP_SHARED) && (addr & (SHMLBA - 1)))
return -EINVAL;
return addr;
}
if (len > TASK_SIZE)
return -ENOMEM;
if (addr) {
if (flags & MAP_PRIVATE)
addr = PAGE_ALIGN(addr);
else
addr = COLOUR_ALIGN(addr);
vma = find_vma(mm, addr);
if (TASK_SIZE - len >= 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
addr = COLOUR_ALIGN(mm->free_area_cache);
start_addr = addr;
full_search:
for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
/* At this point: (!vma || addr < vma->vm_end). */
if (TASK_SIZE - len < addr) {
/*
* Start a new search - just in case we missed
* some holes.
*/
if (start_addr != TASK_UNMAPPED_BASE) {
start_addr = addr = TASK_UNMAPPED_BASE;
mm->cached_hole_size = 0;
goto full_search;
}
return -ENOMEM;
}
if (!vma || addr + len <= vma->vm_start) {
/*
* Remember the place where we stopped the 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);
}
}
#endif
static inline long
do_mmap2(unsigned long addr, unsigned long len, unsigned long prot,
unsigned long flags, int fd, unsigned long pgoff)
{
int error = -EBADF;
struct file *file = NULL;
flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
if (!(flags & MAP_ANONYMOUS)) {
file = fget(fd);
if (!file)
goto out;
}
down_write(&current->mm->mmap_sem);
error = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
up_write(&current->mm->mmap_sem);
if (file)
fput(file);
out:
return error;
}
asmlinkage int old_mmap(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
int fd, unsigned long off)
{
if (off & ~PAGE_MASK)
return -EINVAL;
return do_mmap2(addr, len, prot, flags, fd, off>>PAGE_SHIFT);
}
asmlinkage long sys_mmap2(unsigned long addr, unsigned long len,
unsigned long prot, unsigned long flags,
unsigned long fd, unsigned long pgoff)
{
return do_mmap2(addr, len, prot, flags, fd, pgoff);
}
/*
* sys_ipc() is the de-multiplexer for the SysV IPC calls..
*
* This is really horribly ugly.
*/
asmlinkage int sys_ipc(uint call, int first, int second,
int third, void __user *ptr, long fifth)
{
int version, ret;
version = call >> 16; /* hack for backward compatibility */
call &= 0xffff;
if (call <= SEMCTL)
switch (call) {
case SEMOP:
return sys_semtimedop(first, (struct sembuf __user *)ptr,
second, NULL);
case SEMTIMEDOP:
return sys_semtimedop(first, (struct sembuf __user *)ptr,
second,
(const struct timespec __user *)fifth);
case SEMGET:
return sys_semget (first, second, third);
case SEMCTL: {
union semun fourth;
if (!ptr)
return -EINVAL;
if (get_user(fourth.__pad, (void * __user *) ptr))
return -EFAULT;
return sys_semctl (first, second, third, fourth);
}
default:
return -EINVAL;
}
if (call <= MSGCTL)
switch (call) {
case MSGSND:
return sys_msgsnd (first, (struct msgbuf __user *) ptr,
second, third);
case MSGRCV:
switch (version) {
case 0: {
struct ipc_kludge tmp;
if (!ptr)
return -EINVAL;
if (copy_from_user(&tmp,
(struct ipc_kludge __user *) ptr,
sizeof (tmp)))
return -EFAULT;
return sys_msgrcv (first, tmp.msgp, second,
tmp.msgtyp, third);
}
default:
return sys_msgrcv (first,
(struct msgbuf __user *) ptr,
second, fifth, third);
}
case MSGGET:
return sys_msgget ((key_t) first, second);
case MSGCTL:
return sys_msgctl (first, second,
(struct msqid_ds __user *) ptr);
default:
return -EINVAL;
}
if (call <= SHMCTL)
switch (call) {
case SHMAT:
switch (version) {
default: {
ulong raddr;
ret = do_shmat (first, (char __user *) ptr,
second, &raddr);
if (ret)
return ret;
return put_user (raddr, (ulong __user *) third);
}
case 1: /* iBCS2 emulator entry point */
if (!segment_eq(get_fs(), get_ds()))
return -EINVAL;
return do_shmat (first, (char __user *) ptr,
second, (ulong *) third);
}
case SHMDT:
return sys_shmdt ((char __user *)ptr);
case SHMGET:
return sys_shmget (first, second, third);
case SHMCTL:
return sys_shmctl (first, second,
(struct shmid_ds __user *) ptr);
default:
return -EINVAL;
}
return -EINVAL;
}
asmlinkage int sys_uname(struct old_utsname * name)
{
int err;
if (!name)
return -EFAULT;
down_read(&uts_sem);
err=copy_to_user(name, &system_utsname, sizeof (*name));
up_read(&uts_sem);
return err?-EFAULT:0;
}
asmlinkage ssize_t sys_pread_wrapper(unsigned int fd, char * buf,
size_t count, long dummy, loff_t pos)
{
return sys_pread64(fd, buf, count, pos);
}
asmlinkage ssize_t sys_pwrite_wrapper(unsigned int fd, const char * buf,
size_t count, long dummy, loff_t pos)
{
return sys_pwrite64(fd, buf, count, pos);
}
asmlinkage int sys_fadvise64_64_wrapper(int fd, u32 offset0, u32 offset1,
u32 len0, u32 len1, int advice)
{
#ifdef __LITTLE_ENDIAN__
return sys_fadvise64_64(fd, (u64)offset1 << 32 | offset0,
(u64)len1 << 32 | len0, advice);
#else
return sys_fadvise64_64(fd, (u64)offset0 << 32 | offset1,
(u64)len0 << 32 | len1, advice);
#endif
}