linux-kernel - [PATCH -tip v2 0/5] kprobes: batch (un)optimization support

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Date:	Tue, 18 May 2010 16:12:44 -0400
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>, lkml <linux-kernel@...r.kernel.org>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Jim Keniston <jkenisto@...ibm.com>,
	Jason Baron <jbaron@...hat.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>
Subject: [PATCH -tip v2 0/5] kprobes: batch (un)optimization support

Hi,

Here is the 2nd version of batch optimizing patch series.

Since current kprobes jump optimization calls stop_machine() for each
probe, it can make a lot latency noise when (un)registering a lot of
probes (~1000) at once. For example, on 4 core Xeon, 256 probes
optimization takes 770us in average (max 3.3ms).
This patch series introduces batch (un)optimization which modifies
code with just one stop_machine(), and it improves optimization time
to 90us in average (max 330us).

- Introduce text_poke_smp_batch() which modifies multiple
  codes with one stop_machine().
- Limit how many probes can be (un)optimized at once.
- Introduce delayed unoptimization for batch processing.

text_poke_smp_batch() also helps Jason's Jump label to reduce
its overhead coming from text_poke_smp().

Changes in v2:
- Add kprobes selftest bugfix patch.
- Add some comments about locks according to Mathieu's comment.
- Allocate working buffers when initializing kprobes, instead of
  using static arraies.
- Merge max optimization limit patch into batch optimizing patch.

Thank you,

---

Masami Hiramatsu (5):
      kprobes: Support delayed unoptimization
      kprobes/x86: Use text_poke_smp_batch
      x86: Introduce text_poke_smp_batch() for batch-code modifying
      [CLEANUP] kprobes: Remove redundant text_mutex lock in optimize
      [BUGFIX] kprobes: Fix selftest to clear flags field for reusing probes


 arch/x86/include/asm/alternative.h |    7 +
 arch/x86/include/asm/kprobes.h     |    4 
 arch/x86/kernel/alternative.c      |   49 +++-
 arch/x86/kernel/kprobes.c          |  114 +++++++++
 include/linux/kprobes.h            |    4 
 kernel/kprobes.c                   |  442 ++++++++++++++++++++++++------------
 kernel/test_kprobes.c              |   12 +
 7 files changed, 464 insertions(+), 168 deletions(-)

-- 
Masami Hiramatsu
e-mail: mhiramat@...hat.com
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