665919aaaf
IPI_STOP is used after panic or when ddb is entered manually. MONITOR/ MWAIT allows CPUs that support the feature to sleep in a low power way instead of spinning. Something similar is already used at idle. It is perhaps especially useful in oversubscribed VM environments, and is safe to use even if the panic/ddb thread is not the BSP. (Except in the presence of MWAIT errata, which are detected automatically on platforms with known wakeup problems.) It can be tuned/sysctled with "machdep.stop_mwait," which defaults to 0 (off). This commit also introduces the tunable "machdep.mwait_cpustop_broken," which defaults to 0, unless the CPU has known errata, but may be set to "1" in loader.conf to signal that mwait wakeup is broken on CPUs FreeBSD does not yet know about. Unfortunately, Bhyve doesn't yet support MONITOR extensions, so this doesn't help bhyve hypervisors running FreeBSD guests. Submitted by: Anton Rang <rang AT acm.org> (earlier version) Reviewed by: kib Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D20135 |
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| bios | ||
| cloudabi32 | ||
| conf | ||
| i386 | ||
| include | ||
| linux | ||
| pci | ||
| Makefile | ||