char *cpu_name(struct cpu_info *);
and use it when setting up the runq event counters, avoiding an 8 byte
kmem(4) allocation for each cpu. there are more places the cpuname is
used that can be converted to using this new interface, but that can
and will be done as future work.
as discussed with rmind.
- Addresses the issue described in PR/38828.
- Some simplification in threading and sleepq subsystems.
- Eliminates pmap_collect() and, as a side note, allows pmap optimisations.
- Eliminates XS_CTL_DATA_ONSTACK in scsipi code.
- Avoids few scans on LWP list and thus potentially long holds of proc_lock.
- Cuts ~1.5k lines of code. Reduces amd64 kernel size by ~4k.
- Removes __SWAP_BROKEN cases.
Tested on x86, mips, acorn32 (thanks <mpumford>) and partly tested on
acorn26 (thanks to <bjh21>).
Discussed on <tech-kern>, reviewed by <ad>.
- Change minimal time-quantum to ~20 ms.
- Thus remove unneeded pool in M2, and unused sched_lwp_exit().
- Do not increase l_slptime twice for SCHED_4BSD (regression fix).
mi_switch(), migration for LSONPROC is now performed via idle loop.
Handles/fixes on-CPU case in lwp_migrate(), misc.
Closes PR/38169, idea of migration via idle loop by Andrew Doran.
- Fix performance regression inroduced by the workaround by making job
stealing a lot simpler: if the local run queue is empty, let the CPU enter
the idle loop. In the idle loop, try to steal a job from another CPU's run
queue if we are idle. If we succeed, re-enter mi_switch() immediatley to
dispatch the job.
- When stealing jobs, consider a remote CPU to have one less job in its
queue if it's currently in the idle loop. It will dispatch the job soon,
so there's no point sloshing it about.
- Introduce a few event counters to monitor what's happening with the run
queues.
- Revert the idle CPU bitmap change. It's pointless considering NUMA.
Fail sched_catchlwp() if mutex_tryenter() on the remote CPU's state fails.
Seems to work around the issue described in this PR.
XXX Stealing jobs from remote CPUs could probably be moved into the idle
loop, making the locking quite a bit simpler.
