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Subject[PATCH -tip v4 0/3] Kprobes/x86: Batch optimization support

Here is batch optimizing patch series version 4.

Since current kprobes jump optimization calls stop_machine() for each
probe, it can make a lot of latency noises 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() will also help Jump label to reduce
its delay coming from text_poke_smp().

Changes in v4:
- Update to the latest tip tree.

Changes in v3:
- Set kp.addr = NULL according to Ananth's comment.

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 (3):
kprobes: Support delayed unoptimization
kprobes/x86: Use text_poke_smp_batch
x86: Introduce text_poke_smp_batch() for batch-code modifying

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 | 435 ++++++++++++++++++++++++------------
6 files changed, 451 insertions(+), 162 deletions(-)

2nd Dept. Linux Technology Center
Hitachi, Ltd., Systems Development Laboratory

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