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authorJinghao Jia <jinghao7@illinois.edu>2024-03-07 00:26:01 +0900
committerMasami Hiramatsu (Google) <mhiramat@kernel.org>2024-03-07 00:26:01 +0900
commit290eb13f1a657313177789159a6d1786187cf168 (patch)
tree436442c7955f27dc4d8734685de71edc8729e95f /tools/perf/scripts/python/syscall-counts.py
parente884edbb844fd6935e4368734edd9f3fa46ec5c2 (diff)
x86/kprobes: Boost more instructions from grp2/3/4/5
With the instruction decoder, we are now able to decode and recognize instructions with opcode extensions. There are more instructions in these groups that can be boosted: Group 2: ROL, ROR, RCL, RCR, SHL/SAL, SHR, SAR Group 3: TEST, NOT, NEG, MUL, IMUL, DIV, IDIV Group 4: INC, DEC (byte operation) Group 5: INC, DEC (word/doubleword/quadword operation) These instructions are not boosted previously because there are reserved opcodes within the groups, e.g., group 2 with ModR/M.nnn == 110 is unmapped. As a result, kprobes attached to them requires two int3 traps as being non-boostable also prevents jump-optimization. Some simple tests on QEMU show that after boosting and jump-optimization a single kprobe on these instructions with an empty pre-handler runs 10x faster (~1000 cycles vs. ~100 cycles). Since these instructions are mostly ALU operations and do not touch special registers like RIP, let's boost them so that we get the performance benefit. Link: https://lore.kernel.org/all/20240204031300.830475-4-jinghao7@illinois.edu/ Signed-off-by: Jinghao Jia <jinghao7@illinois.edu> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
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