Stop side exit tracing when reach max_root_trace #9964
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When max_root_trace is reached, tracing JIT will not compile any new code for side trace, but side exit tracing is still going on. Stop it immediately instead of lazy blacklisting. This reduces JIT cost and potentially improve PHP execution efficiency. Signed-off-by: Wang, Xue <[email protected]> Reviewed-by: Chen, Hu <[email protected]> Reviewed-by: Su, Tao <[email protected]>
dstogov
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Nov 21, 2022
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I'm not sure if this is the right decision.
Blacklisting includes code generation for deoptimization. This is not a cheap process and doing this for all side exits at once may take significant time. Many side exits are never used and code generation for them is useless and will lead to additional code bloat.
I'm open for your arguments.
| /* Traverse all JITed code, restore side exit to vm execution */ | ||
| for (i = 1; i < ZEND_JIT_TRACE_NUM; i++) { | ||
| for (j = 0; j < zend_jit_traces[i].exit_count; j++) { | ||
| zend_jit_blacklist_trace_exit(i, j); |
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It makes sense to avoid calling zend_jit_blacklist_trace_exit() for already jit-ed and blacklisted side exits. This would remove unnecessary locks.
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When max_root_trace is reached, tracing JIT will not compile any new code for side trace, but side exit tracing is still going on. Stop it immediately instead of lazy blacklisting. This reduces JIT cost and potentially improve PHP execution efficiency.
Signed-off-by: Wang, Xue [email protected]
Reviewed-by: Chen, Hu [email protected]
Reviewed-by: Su, Tao [email protected]