Module Name: src
Committed By: martin
Date: Sat Sep 21 12:20:23 UTC 2024
Modified Files:
src/sys/arch/amd64/amd64 [netbsd-10]: db_interface.c
src/sys/arch/i386/i386 [netbsd-10]: db_interface.c
Log Message:
Pull up following revision(s) (requested by rin in ticket #900):
sys/arch/amd64/amd64/db_interface.c: revision 1.42
sys/arch/i386/i386/db_interface.c: revision 1.89
when cpus are paused (spinning) in DDB, call x86_pause() in the loop,
hopefully this can reduce power usage while doing nothing.
ok chs@
XXX: apply to i386
i386: DDB: Call x86_pause() (`pause` insn) when CPUs are paused
as already done for amd64:
https://mail-index.netbsd.org/source-changes/2023/07/31/msg146423.html
`pause` insn has been introduced to Pentium 4. However, its opcode is
consisted of `nop` (0x90) followed by `rep` prefix (0xf3), and therefore
interpreted as `nop` for older processors. Intel assured this behavior [1].
Also note that we already use `pause` unconditionally for i386.
Briefly tested on QEMU.
[1] Intel, ``AP-949 Using Spin-Loops on Intel Pentium 4 Processor and
Intel Xeon Processor'', Version 2.1, Sec 2.1.1. (2001)
To generate a diff of this commit:
cvs rdiff -u -r1.41 -r1.41.2.1 src/sys/arch/amd64/amd64/db_interface.c
cvs rdiff -u -r1.88 -r1.88.2.1 src/sys/arch/i386/i386/db_interface.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
