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  1. 16 Jan, 2017 3 commits
  3. 14 Jan, 2017 1 commit
    • Masami Hiramatsu's avatar
      kprobes, extable: Identify kprobes trampolines as kernel text area · 5b485629
      Masami Hiramatsu authored 
      Improve __kernel_text_address()/kernel_text_address() to return
true if the given address is on a kprobe's instruction slot
trampoline.

This can help stacktraces to determine the address is on a
text area or not.

To implement this atomically in is_kprobe_*_slot(), also change
the insn_cache page list to an RCU list.

This changes timings a bit (it delays page freeing to the RCU garbage
collection phase), but none of that is in the hot path.

Note: this change can add small overhead to stack unwinders because
it adds 2 additional checks to __kernel_text_address(). However, the
impact should be very small, because kprobe_insn_pages list has 1 entry
per 256 probes(on x86, on arm/arm64 it will be 1024 probes),
and kprobe_optinsn_pages has 1 entry per 32 probes(on x86).
In most use cases, the number of kprobe events may be less
than 20, which means that is_kprobe_*_slot() will check just one entry.
Tested-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/148388747896.6869.6354262871751682264.stgit@devbox
[ Improved the changelog and coding style. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      5b485629
  5. 12 Jan, 2017 1 commit
    • Ingo Molnar's avatar
      Merge tag 'perf-core-for-mingo-4.11-20170111' of... · f913f3a6
      Ingo Molnar authored 
      Merge tag 'perf-core-for-mingo-4.11-20170111' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/core

Pull perf/core improvements and fixes from Arnaldo Carvalho de Melo:

New features:

- Add more triggers to switch the output file (perf.data.TIMESTAMP).

  Now, in addition to switching to a different output file when
  receiving a SIGUSR2, one can also specify file size and time based
  triggers:

       perf record -a --switch-output=signal

  is equivalent to what we had before:

       perf record -a --switch-output

  While we can also ask for the file to be "sliced" by size, taking
  into account that that will happen only when we get woken up by
  the kernel, i.e. one has to take into account the --mmap-pages (the
  size of the perf mmap ring buffer):

       perf record -a --switch-output=2G

  will break the perf.data output into multiple files limited to 2GB
  of samples, right when generating the output.

  For time based samples, alert() will be used, so to have 1 minute
  limited perf.data output files:

      perf record -a --switch-output=1m

  (Jiri Olsa)

- Remove the need to use -e only for syscalls and --event only for
  tracepoints/HW/SW/etc events, i.e. now one can use:

      perf trace -e nanosleep,futex,sched:sched_switch ./workload

  or:

      perf trace --event nanosleep,futex,sched:sched_switch ./workload

  And have it tracing raw_syscalls:sys_{enter,exit} for the nanosleep
  and futex syscalls, formatting those as strace does while also
  tracing sched:sched_switch, ordering it all into one strace like
  output.

  Using '!' as the first character in the -e/--event argument remains
  a way to negate the list of syscalls, i.e. all syscalls except for
  the ones specified, doesn't affect the other kinds of events.

  E.g:

  [root@jouet ~] # perf trace -e sched:sched_switch,nanosleep usleep 1
     0.000 ( 0.028 ms): usleep/28150 nanosleep(rqtp: 0x7ffe4201b9f0) ...
     0.028 (         ): sched:sched_switch:usleep:28150 [120] S ==> swapper/0:0 [120])
     0.000 ( 0.065 ms): usleep/28150  ... [continued]: nanosleep()) = 0
  [root@jouet ~]#

  (Arnaldo Carvalho de Melo)

- 'perf kallsyms' toy tool to look for extended symbol information on
  the running kernel and demonstrate the machine/thread/symbol APIs for
  use in other tools, such as 'perf probe' (Arnaldo Carvalho de Melo)

Infrastructure improvements:

- Add missing linux/kernel.h include to subcmd.h (Arnaldo Carvalho de Melo)
  tools: Sync x86's vmx.h with the kernel

- Create libdir directory before installing libperf-jvmti.so (Laura Abbott)

- Fix typo in perf_evlist__start_workload() (Soramichi Akiyama)
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      f913f3a6
  7. 11 Jan, 2017 15 commits
  9. 05 Jan, 2017 2 commits
    • David Carrillo-Cisneros's avatar
      perf/x86: Set pmu->module in Intel PMU modules · 74545f63
      David Carrillo-Cisneros authored 
      The conversion of Intel PMU drivers into modules did not include reference
counting. The machine will crash when attempting to  access deleted code
if an event from a module PMU is started and the module removed before the
event is destroyed.

i.e. this crashes the machine:

	$ insmod intel-rapl-perf.ko
	$ perf stat -e power/energy-cores/ -C 0 &
	$ rmmod intel-rapl-perf.ko

Set THIS_MODULE to pmu->module in Intel module PMUs so that generic code
can handle reference counting and deny rmmod while an event still exists.
Signed-off-by: default avatarDavid Carrillo-Cisneros <davidcc@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1482455860-116269-1-git-send-email-davidcc@google.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      74545f63
    • Ingo Molnar's avatar
      Merge tag 'perf-urgent-for-mingo-4.10-20170104' of... · 4e06d4f0
      Ingo Molnar authored 
      Merge tag 'perf-urgent-for-mingo-4.10-20170104' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent

Pull perf/urgent fixes and one improvement from Arnaldo Carvalho de Melo:

Fixes:

  - Fix prev/next_prio formatting for deadline tasks in libtraceevent (Daniel Bristot de Oliveira)

  - Robustify reading of build-ids from /sys/kernel/note (Arnaldo Carvalho de Melo)

  - Fix building some sample/bpf in Alpine Linux 3.4 (Arnaldo Carvalho de Melo)

  - Fix 'make install-bin' to install libtraceevent plugins (Arnaldo Carvalho de Melo)

  - Fix 'perf record --switch-output' documentation and comment (Jiri Olsa)

  - Fix 'perf probe' for cross arch probing (Masami Hiramatsu)

Improvement:

  - Show total scheduling time in 'perf sched timehist' (Namhyumg Kim)
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      4e06d4f0
  11. 04 Jan, 2017 2 commits
  13. 03 Jan, 2017 6 commits
  15. 02 Jan, 2017 1 commit
    • Masami Hiramatsu's avatar
      perf probe: Fix to get correct modname from elf header · 1f2ed153
      Masami Hiramatsu authored 
      Since 'perf probe' supports cross-arch probes, it is possible to analyze
different arch kernel image which has different bits-per-long.

In that case, it fails to get the module name because it uses the
MOD_NAME_OFFSET macro based on the host machine bits-per-long, instead
of the target arch bits-per-long.

This fixes above issue by changing modname-offset based on the target
archs bit width. This is ok because linux kernel uses LP64 model on
64bit arch.

E.g. without this (on x86_64, and target module is arm32):

  $ perf probe -m build-arm/fs/configfs/configfs.ko -D configfs_lookup
  p:probe/configfs_lookup :configfs_lookup+0
                          ^-Here is an empty module name.

With this fix, you can see correct module name:

  $ perf probe -m build-arm/fs/configfs/configfs.ko -D configfs_lookup
  p:probe/configfs_lookup configfs:configfs_lookup+0
Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/148337043836.6752.383495516397005695.stgit@devboxSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      1f2ed153
  17. 01 Jan, 2017 2 commits
    • Linus Torvalds's avatar
      Linux 4.10-rc2 · 0c744ea4
      Linus Torvalds authored
      0c744ea4
    • Linus Torvalds's avatar
      Merge branch 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm · 4759d386
      Linus Torvalds authored 
      Pull DAX updates from Dan Williams:
 "The completion of Jan's DAX work for 4.10.

  As I mentioned in the libnvdimm-for-4.10 pull request, these are some
  final fixes for the DAX dirty-cacheline-tracking invalidation work
  that was merged through the -mm, ext4, and xfs trees in -rc1. These
  patches were prepared prior to the merge window, but we waited for
  4.10-rc1 to have a stable merge base after all the prerequisites were
  merged.

  Quoting Jan on the overall changes in these patches:

     "So I'd like all these 6 patches to go for rc2. The first three
      patches fix invalidation of exceptional DAX entries (a bug which
      is there for a long time) - without these patches data loss can
      occur on power failure even though user called fsync(2). The other
      three patches change locking of DAX faults so that ->iomap_begin()
      is called in a more relaxed locking context and we are safe to
      start a transaction there for ext4"

  These have received a build success notification from the kbuild
  robot, and pass the latest libnvdimm unit tests. There have not been
  any -next releases since -rc1, so they have not appeared there"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  ext4: Simplify DAX fault path
  dax: Call ->iomap_begin without entry lock during dax fault
  dax: Finish fault completely when loading holes
  dax: Avoid page invalidation races and unnecessary radix tree traversals
  mm: Invalidate DAX radix tree entries only if appropriate
  ext2: Return BH_New buffers for zeroed blocks
      4759d386
  19. 30 Dec, 2016 2 commits
  21. 29 Dec, 2016 2 commits
    • Olof Johansson's avatar
      mm/filemap: fix parameters to test_bit() · 98473f9f
      Olof Johansson authored 
       mm/filemap.c: In function 'clear_bit_unlock_is_negative_byte':
  mm/filemap.c:933:9: error: too few arguments to function 'test_bit'
    return test_bit(PG_waiters);
         ^~~~~~~~

Fixes: b91e1302 ('mm: optimize PageWaiters bit use for unlock_page()')
Signed-off-by: default avatarOlof Johansson <olof@lixom.net>
Brown-paper-bag-by: default avatarLinus Torvalds <dummy@duh.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      98473f9f
    • Linus Torvalds's avatar
      mm: optimize PageWaiters bit use for unlock_page() · b91e1302
      Linus Torvalds authored 
      In commit 62906027 ("mm: add PageWaiters indicating tasks are
waiting for a page bit") Nick Piggin made our page locking no longer
unconditionally touch the hashed page waitqueue, which not only helps
performance in general, but is particularly helpful on NUMA machines
where the hashed wait queues can bounce around a lot.

However, the "clear lock bit atomically and then test the waiters bit"
sequence turns out to be much more expensive than it needs to be,
because you get a nasty stall when trying to access the same word that
just got updated atomically.

On architectures where locking is done with LL/SC, this would be trivial
to fix with a new primitive that clears one bit and tests another
atomically, but that ends up not working on x86, where the only atomic
operations that return the result end up being cmpxchg and xadd.  The
atomic bit operations return the old value of the same bit we changed,
not the value of an unrelated bit.

On x86, we could put the lock bit in the high bit of the byte, and use
"xadd" with that bit (where the overflow ends up not touching other
bits), and look at the other bits of the result.  However, an even
simpler model is to just use a regular atomic "and" to clear the lock
bit, and then the sign bit in eflags will indicate the resulting state
of the unrelated bit #7.

So by moving the PageWaiters bit up to bit #7, we can atomically clear
the lock bit and test the waiters bit on x86 too.  And architectures
with LL/SC (which is all the usual RISC suspects), the particular bit
doesn't matter, so they are fine with this approach too.

This avoids the extra access to the same atomic word, and thus avoids
the costly stall at page unlock time.

The only downside is that the interface ends up being a bit odd and
specialized: clear a bit in a byte, and test the sign bit.  Nick doesn't
love the resulting name of the new primitive, but I'd rather make the
name be descriptive and very clear about the limitation imposed by
trying to work across all relevant architectures than make it be some
generic thing that doesn't make the odd semantics explicit.

So this introduces the new architecture primitive

    clear_bit_unlock_is_negative_byte();

and adds the trivial implementation for x86.  We have a generic
non-optimized fallback (that just does a "clear_bit()"+"test_bit(7)"
combination) which can be overridden by any architecture that can do
better.  According to Nick, Power has the same hickup x86 has, for
example, but some other architectures may not even care.

All these optimizations mean that my page locking stress-test (which is
just executing a lot of small short-lived shell scripts: "make test" in
the git source tree) no longer makes our page locking look horribly bad.
Before all these optimizations, just the unlock_page() costs were just
over 3% of all CPU overhead on "make test".  After this, it's down to
0.66%, so just a quarter of the cost it used to be.

(The difference on NUMA is bigger, but there this micro-optimization is
likely less noticeable, since the big issue on NUMA was not the accesses
to 'struct page', but the waitqueue accesses that were already removed
by Nick's earlier commit).
Acked-by: default avatarNick Piggin <npiggin@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      b91e1302
  23. 28 Dec, 2016 3 commits
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