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  1. 11 Nov, 2009 1 commit
    • Oleg Nesterov's avatar
      If the tracee calls fork() after PTRACE_SINGLESTEP, the forked child · 17c18328
      Oleg Nesterov authored 
      starts with TIF_SINGLESTEP/X86_EFLAGS_TF bits copied from ptraced parent. 
This is not right, especially when the new child is not auto-attaced: in
this case it is killed by SIGTRAP.

Change copy_process() to call user_disable_single_step(). Tested on x86.

Test-case:

	#include <stdio.h>
	#include <unistd.h>
	#include <signal.h>
	#include <sys/ptrace.h>
	#include <sys/wait.h>
	#include <assert.h>

	int main(void)
	{
		int pid, status;

		if (!(pid = fork())) {
			assert(ptrace(PTRACE_TRACEME) == 0);
			kill(getpid(), SIGSTOP);

			if (!fork()) {
				/* kernel bug: this child will be killed by SIGTRAP */
				printf("Hello world\n");
				return 43;
			}

			wait(&status);
			return WEXITSTATUS(status);
		}

		for (;;) {
			assert(pid == wait(&status));
			if (WIFEXITED(status))
				break;
			assert(ptrace(PTRACE_SINGLESTEP, pid, 0,0) == 0);
		}

		assert(WEXITSTATUS(status) == 43);
		return 0;
	}
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      17c18328
  3. 30 Oct, 2009 1 commit
  5. 12 Nov, 2009 3 commits
  7. 11 Nov, 2009 1 commit
  9. 16 Oct, 2009 1 commit
  11. 10 Oct, 2009 2 commits
    • Andrew Morton's avatar
      tweak comments · 8dd9b428
      Andrew Morton authored 
      Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      8dd9b428
    • KAMEZAWA Hiroyuki's avatar
      This is a patch for coalescing access to res_counter at charging by percpu · a2a2551f
      KAMEZAWA Hiroyuki authored 
      caching.  At charge, memcg charges 64pages and remember it in percpu
cache.  Because it's cache, drain/flush if necessary.

This version uses public percpu area.
 2 benefits for using public percpu area.
 1. Sum of stocked charge in the system is limited to # of cpus
    not to the number of memcg. This shows better synchonization.
 2. drain code for flush/cpuhotplug is very easy (and quick)

The most important point of this patch is that we never touch res_counter
in fast path. The res_counter is system-wide shared counter which is modified
very frequently. We shouldn't touch it as far as we can for avoiding
false sharing.

On x86-64 8cpu server, I tested overheads of memcg at page fault by
running a program which does map/fault/unmap in a loop. Running
a task per a cpu by taskset and see sum of the number of page faults
in 60secs.

[without memcg config]
  40156968  page-faults              #      0.085 M/sec   ( +-   0.046% )
  27.67 cache-miss/faults

[root cgroup]
  36659599  page-faults              #      0.077 M/sec   ( +-   0.247% )
  31.58 cache miss/faults

[in a child cgroup]
  18444157  page-faults              #      0.039 M/sec   ( +-   0.133% )
  69.96 cache miss/faults

[ + coalescing uncharge patch]
  27133719  page-faults              #      0.057 M/sec   ( +-   0.155% )
  47.16 cache miss/faults

[ + coalescing uncharge patch + this patch ]
  34224709  page-faults              #      0.072 M/sec   ( +-   0.173% )
  34.69 cache miss/faults

Changelog (since Oct/2):
  - updated comments
  - replaced get_cpu_var() with __get_cpu_var() if possible.
  - removed mutex for system-wide drain. adds a counter instead of it.
  - removed CONFIG_HOTPLUG_CPU

Changelog (old):
  - rebased onto the latest mmotm
  - moved charge size check before __GFP_WAIT check for avoiding unnecesary
  - added asynchronous flush routine.
  - fixed bugs pointed out by Nishimura-san.
Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      a2a2551f
  13. 11 Nov, 2009 1 commit
    • KAMEZAWA Hiroyuki's avatar
      In massive parallel enviroment, res_counter can be a performance · 92501285
      KAMEZAWA Hiroyuki authored 
      bottleneck.  One strong techinque to reduce lock contention is reducing
calls by coalescing some amount of calls into one.

Considering charge/uncharge chatacteristic,
	- charge is done one by one via demand-paging.
	- uncharge is done by
		- in chunk at munmap, truncate, exit, execve...
		- one by one via vmscan/paging.

It seems we have a chance to coalesce uncharges for improving scalability
at unmap/truncation.

This patch is a for coalescing uncharge.  For avoiding scattering memcg's
structure to functions under /mm, this patch adds memcg batch uncharge
information to the task.  A reason for per-task batching is for making use
of caller's context information.  We do batched uncharge (deleyed
uncharge) when truncation/unmap occurs but do direct uncharge when
uncharge is called by memory reclaim (vmscan.c).

The degree of coalescing depends on callers
  - at invalidate/trucate... pagevec size
  - at unmap ....ZAP_BLOCK_SIZE
(memory itself will be freed in this degree.)
Then, we'll not coalescing too much.

On x86-64 8cpu server, I tested overheads of memcg at page fault by
running a program which does map/fault/unmap in a loop. Running
a task per a cpu by taskset and see sum of the number of page faults
in 60secs.

[without memcg config]
  40156968  page-faults              #      0.085 M/sec   ( +-   0.046% )
  27.67 cache-miss/faults
[root cgroup]
  36659599  page-faults              #      0.077 M/sec   ( +-   0.247% )
  31.58 miss/faults
[in a child cgroup]
  18444157  page-faults              #      0.039 M/sec   ( +-   0.133% )
  69.96 miss/faults
[child with this patch]
  27133719  page-faults              #      0.057 M/sec   ( +-   0.155% )
  47.16 miss/faults

We can see some amounts of improvement.
(root cgroup doesn't affected by this patch)
Another patch for "charge" will follow this and above will be improved more.

Changelog(since 2009/10/02):
 - renamed filed of memcg_batch (as pages to bytes, memsw to memsw_bytes)
 - some clean up and commentary/description updates.
 - added initialize code to copy_process(). (possible bug fix)

Changelog(old):
 - fixed !CONFIG_MEM_CGROUP case.
 - rebased onto the latest mmotm + softlimit fix patches.
 - unified patch for callers
 - added commetns.
 - make ->do_batch as bool.
 - removed css_get() at el. We don't need it.
Signed-off-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      92501285
  15. 10 Nov, 2009 1 commit
  17. 03 Nov, 2009 1 commit
  19. 25 Sep, 2009 1 commit
  21. 13 Nov, 2009 1 commit
  23. 11 Nov, 2009 1 commit
  25. 14 Oct, 2009 1 commit
  27. 11 Nov, 2009 1 commit
  29. 10 Nov, 2009 2 commits
  31. 25 Sep, 2009 1 commit
  33. 21 Nov, 2008 1 commit
    • Warren Turkal's avatar
      This is a patchset to change the way that the HFS+ filesystem detects · fced310a
      Warren Turkal authored 
      whether a volume has a journal or not.

The code currently mounts an HFS+ volume read-only by default when a
journal is detected.  One can force a read/write mount by giving the
"force" mount option.  The current code has this behavior since there is
no support for the HFS+ journal.

My problem is that the detection of the journal could be better.  The
current code tests the attribute bit in the volume header that indicates
there is a journal.  If that bit is set, the code assumes that there is a
journal.

Unfortunately, this is not enough to really determine if there is a
journal or not.  When that bit is set, one must also examine the journal
info block field of the volume header.  If this field is 0, there is no
journal, and the volume can be mounted read/write.


This patch:

The HFS+ support in the kernel currently will mount an HFS+ volume
read-only if the volume header has the attribute bit set that indicates
there is a journal.  The kernel does this because there is no support for
a journalled HFS+ volume.

The problem is that this is only half of what needs to be checked to see
if there really is a journal.  There is also an entry in the volume header
that tells you where to find the journal info block.  In the kernel
version of the kernel, this 4 byte block is labeled reserved.  This patch
identifies the journal info block in the header.
Signed-off-by: default avatarWarren Turkal <wt@penguintechs.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      fced310a
  35. 03 Nov, 2009 2 commits
  37. 16 Oct, 2009 1 commit
  39. 17 Sep, 2009 1 commit
  41. 13 Nov, 2009 1 commit
  43. 10 Nov, 2009 1 commit
  45. 16 Nov, 2009 1 commit
  47. 11 Nov, 2009 1 commit
  49. 03 Nov, 2009 5 commits
  51. 14 Oct, 2009 1 commit
  53. 24 Sep, 2009 2 commits
  55. 14 Oct, 2009 1 commit
  57. 24 Sep, 2009 1 commit
  59. 25 Sep, 2009 1 commit