Optimize set_syscall_retval for riscv
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Authored by trasz on Oct 28 2020, 7:43 PM.

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Reviewers

mhorne
kp

Group Reviewers

riscv

Commits

rS367138: Optimize set_syscall_retval for riscv by predicting the return

Summary

Optimize set_syscall_retval for riscv by predicting the return
value to be zero.

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Repository

rS FreeBSD src repository - subversion

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Buildable 34448
Build 31550: arc lint + arc unit

Event Timeline

trasz created this revision.Oct 28 2020, 7:43 PM

Herald added a subscriber: imp. · View Herald TranscriptOct 28 2020, 7:43 PM

Harbormaster completed remote builds in B34448: Diff 78864.Oct 28 2020, 7:43 PM

trasz requested review of this revision.Oct 28 2020, 7:43 PM

trasz added a reviewer: riscv.Oct 28 2020, 7:44 PM

LGTM

This revision is now accepted and ready to land.Oct 28 2020, 8:48 PM

Do we see measurable performance improvements with this?

(Looking at the generated code it does seem to be better, but measurements would make me feel better.)

I wouldn’t expect any visible results. The syscall path overhead is still huge, and there’s not a single reason for it - it’s a “death by thousand cuts” situation, which needs to be resolved in small chunks, like this one.

Closed by commit rS367138: Optimize set_syscall_retval for riscv by predicting the return (authored by trasz). · Explain WhyOct 29 2020, 3:36 PM

This revision was automatically updated to reflect the committed changes.

trasz added a commit: rS367138: Optimize set_syscall_retval for riscv by predicting the return.

Revision Contents
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Path

Size

sys/

riscv/

vm_machdep.c

8 lines

Diff 78864

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sys/riscv/riscv/vm_machdep.c

Optimize set_syscall_retval for riscvClosedPublicActions