but committing it helps to get everyone on the same page and makes
sure we make progress.
Tinderbox breakages that are the result of this commit are entirely
the committer's fault -- in other words: buildworld testing on amd64
only.
Credits follow:
Submitted by: Garrett Cooper <yanegomi@gmail.com>
Sponsored by: Isilon Systems
Based on work by: keramida@
Thanks to: gnn@, mdf@, mlaier@, sjg@
Special thanks to: keramida@
.. so that consistent compilation algorithms are used for both
architectures as in practice the binaries are expected to be
interchangeable (for time being).
Previously i386 used default setting which were equivalent to
-march=i486 -mtune=generic.
The only difference is using smaller but slower "leave" instructions.
Discussed with: jhb, dim
MFC after: 29 days
output and replace it with a new visible sysctl kern.ipc.acceptqueue
of the same functionality. It specifies the maximum length of the
accept queue on a listen socket.
The old kern.ipc.somaxconn remains available for reading and writing
for compatibility reasons so that existing programs, scripts and
configurations continue to work. There no plans to ever remove the
orginal and now hidden kern.ipc.somaxconn.
The reason for this is that the SPARC v9 architecture allows nested
interrupts of higher priority/level than that of the current interrupt
to occur (and we can't just entirely bypass this model, also, at least
for tick interrupts, this also wouldn't be wise). However, when a
preemption interrupt interrupts another interrupt of lower priority,
f.e. PIL_ITHREAD, and that one in turn is nested by a third interrupt,
f.e. PIL_TICK, with SCHED_ULE the execution of interrupts higher than
PIL_PREEMPT may be migrated to another CPU. In particular, tl1_ret(),
which is responsible for restoring the state of the CPU prior to entry
to the interrupt based on the (also migrated) trap frame, then is run
on a CPU which actually didn't receive the interrupt in question,
causing an inappropriate processor interrupt level to be "restored".
In turn, this causes interrupts of the first level, i.e. PIL_ITHREAD
in the above scenario, to be blocked on the target of the migration
until the correct PIL happens to be restored again on that CPU again.
Making PIL_PREEMPT the lowest real priority, this effectively prevents
this scenario from happening, as preemption interrupts no longer can
interrupt any other interrupt besides stray ones (which is no issue).
Thanks to attilio@ and especially mav@ for helping me to understand
this problem at the 201208DevSummit.
- Give PIL_STOP (which is also used for IPI_STOP_HARD, given that there's
no real equivalent to NMIs on SPARC v9) the highest possible priority
just below the hardwired PIL_TICK, so it has a chance to interrupt
more things.
MFC after: 1 week
In addition to adding missing `static' keywords:
- bin/dd: Pull in `extern.h' to guarantee consistency with source file.
- libexec/rpc.rusersd: Move shared globals into an extern.h.
- libexec/talkd: Move `debug' and `hostname' into extern.h.
- usr.bin/cksum: Put counters in extern.h, as they are used by ckdist/mtree.
- usr.bin/m4: Move `end_result' into extern.h.
- usr.sbin/services_mkdb: Move shared globals into an extern.h.
... otherwise the current thread might be holding ARC locks and thus run
into a deadlock. This happens, for example, when a thread does memory
allocation in the ARC code and runs into KVA shortage.
Also, it really makes the most sense to wait in pageproc, so that the
results of ARC reclamation are seen before the page cache is acted upon.
In other cases where vm_lowmem is invoked, e.g. on KVA space shortage,
the callers perform multiple attempts (up to 8) and wait for rather
long intervals between them (up to 4 seconds), so ARC reclaim results
should become visible even without explicit waiting on the ARC thread.
Note that this is not a critical issue for typical ZFS usages where KVA
space should already be large enough. On amd64 systems setting KVA size
to twice the physical memory size is known to mitigate KVA fragmentation
issues in practice.
Side note: perhaps vm_lowmem 'how' parameter should be used to
differentiate between causes of the event.
Reported by: Nikolay Denev <ndenev@gmail.com>
MFC after: 19 days
