(and pollts(2)) are similar to sigsuspend(2) in that they temporarily change
the process signal mask and wait for signal delivery. Factor out and share the
code that does this.
that scheduler locks are special in this regard - adaptive locks cannot
be in the path due to turnstiles. Randomly spotted/reported by uebayasi@.
- Remove unused lwp_relock() and replace lwp_lock_retry() by simplifying
lwp_lock() and sleepq_enter() a little.
- Give alllwp its own cache-line and mark lwp_cache pointer as read-mostly.
OK ad@
pipe subsystems. Avoids overhead of second selscan() on wake-up, and thus
improves performance on certain workloads (especially when polling on many
file-descriptors). Also, clean-up sys/fd_set.h header and improve macros.
Welcome to 5.99.36!
open files is rather gross - the poll map isn't required to be dense.
Instead limit to a much larger value (1000 + dt_nfiles) so that user
programs cannot allocate indefinite sized blocks of kvm.
If the limit is exceeded, then return EINVAL instead of silently truncating
the list.
(The silent truncation in select isn't quite as bad - although even there
any high bits that are set ought to generate an EBADF response.)
Move the code that converts ERESTART and EWOULDBLOCK into common code.
Effectively fixes PR/17507 since the new limit is unlikely to be detected.
- 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>.
- Avoid atomics in more places.
- Remove the per-descriptor mutex, and just use filedesc_t::fd_lock.
It was only being used to synchronize close, and in any case we needed
to take fd_lock to free the descriptor slot.
- Optimize certain paths for the <NDFDFILE case.
- Sprinkle more comments and assertions.
- Cache more stuff in filedesc_t.
- Fix numerous minor bugs spotted along the way.
- Restructure how the open files array is maintained, for clarity and so
that we can eliminate the membar_consumer() call in fd_getfile(). This is
mostly syntactic sugar; the main functional change is that fd_nfiles now
lives alongside the open file array.
Some measurements with libmicro:
- simple file syscalls are like close() are between 1 to 10% faster.
- some nice improvements, e.g. poll(1000) which is ~50% faster.
we no longer need to guard against access from hardware interrupt handlers.
Additionally, if cloning a process with CLONE_SIGHAND, arrange to have the
child process share the parent's lock so that signal state may be kept in
sync. Partially addresses PR kern/37437.
