a 32-bit one. This can cause weird timeout issues, as the copying reads
garbage from the user.
Code by: Deepak Veliath <deepak dot veliath at isilon dot com>
MFC after: 1 week
It is possible a lower priority thread lending priority to higher priority
thread, in old code, it is ignored, however the lending should always be
recorded, add field td_lend_user_pri to fix the problem, if a thread does
not have borrowed priority, its value is PRI_MAX.
MFC after: 1 week
rwlock to protect the table. In old code, thread lookup is done with
process lock held, to find a thread, kernel has to iterate through
process and thread list, this is quite inefficient.
With this change, test shows in extreme case performance is
dramatically improved.
Earlier patch was reviewed by: jhb, julian
for upcoming 64-bit PowerPC and MIPS support. This renames the COMPAT_IA32
option to COMPAT_FREEBSD32, removes some IA32-specific code from MI parts
of the kernel and enhances the freebsd32 compatibility code to support
big-endian platforms.
Reviewed by: kib, jhb
processes to share semaphore by using shared memory area, in simplest case,
only one atomic operation is needed in userland, waiter flag is maintained by
kernel and userland only checks the flag, if the flag is set, user code enters
kernel and does a wakeup() call.
Move type definitions into file _umtx.h to minimize compiling time.
Also type names need to be prefixed with underline character, this would reduce
name conflict (still in progress).
check if there are readers blocked by us via URWLOCK_WRITE_WAITERS flag,
and resume the readers. The error must be EAGAIN, otherwise there must
have memory problem, and nobody can rescue the buggy application.
The revision 197445 might be reverted.
locked and unlocked completely in userland. by locking and unlocking mutex
in userland, it reduces the total time a mutex is locked by a thread,
in some application code, a mutex only protects a small piece of code, the
code's execution time is less than a simple system call, if a lock contention
happens, however in current implemenation, the lock holder has to extend its
locking time and enter kernel to unlock it, the change avoids this disadvantage,
it first sets mutex to free state and then enters kernel and wake one waiter
up. This improves performance dramatically in some sysbench mutex tests.
Tested by: kris
Sounds great: jeff
- Use a global umtx spinlock to protect the sleep queues now that there
is no global scheduler lock.
- Use thread_lock() to protect thread state.
Tested by: kris, current@
Tested on: i386, amd64, ULE, 4BSD, libthr, libkse, PREEMPTION, etc.
Discussed with: kris, attilio, kmacy, jhb, julian, bde (small parts each)
- Remove also "MP SAFE" after prior "MPSAFE" pass. (suggested by bde)
- Remove extra blank lines in some cases.
- Add extra blank lines in some cases.
- Remove no-op comments consisting solely of the function name, the word
"syscall", or the system call name.
- Add punctuation.
- Re-wrap some comments.
running thread's id on each cpu. This allow us to add in-kernel adaptive
spin for user level mutex. While spinning in user space is possible,
without correct thread running state exported from kernel, it hardly
can be implemented efficiently without wasting cpu cycles, however
exporting thread running state unlikely will be implemented soon as
it has to design and stablize interfaces. This implementation is
transparent to user space, it can be disabled dynamically. With this
change, mutex ping-pong program's performance is improved massively on
SMP machine. performance of mysql super-smack select benchmark is increased
about 7% on Intel dual dual-core2 Xeon machine, it indicates on systems
which have bunch of cpus and system-call overhead is low (athlon64, opteron,
and core-2 are known to be fast), the adaptive spin does help performance.
Added sysctls:
kern.threads.umtx_dflt_spins
if the sysctl value is non-zero, a zero umutex.m_spincount will
cause the sysctl value to be used a spin cycle count.
kern.threads.umtx_max_spins
the sysctl sets upper limit of spin cycle count.
Tested on: Athlon64 X2 3800+, Dual Xeon 5130
Make part of John Birrell's KSE patch permanent..
Specifically, remove:
Any reference of the ksegrp structure. This feature was
never fully utilised and made things overly complicated.
All code in the scheduler that tried to make threaded programs
fair to unthreaded programs. Libpthread processes will already
do this to some extent and libthr processes already disable it.
Also:
Since this makes such a big change to the scheduler(s), take the opportunity
to rename some structures and elements that had to be moved anyhow.
This makes the code a lot more readable.
The ULE scheduler compiles again but I have no idea if it works.
The 4bsd scheduler still reqires a little cleaning and some functions that now do
ALMOST nothing will go away, but I thought I'd do that as a separate commit.
Tested by David Xu, and Dan Eischen using libthr and libpthread.
pthread_cancel()ed, it is expected that the thread will not
consume a pthread_cond_signal(), therefor, we use thr_wake()
to mark a flag, the flag tells a thread calling do_cv_wait()
in umtx code to not block on a condition variable.
Thread library is expected that once a thread detected itself
is in pthread_cond_wait, it will call the thr_wake() for itself
in its SIGCANCEL handler.
priority mutex implemented, it is the time to introduce this stuff,
now we can use umutex and ucond together to implement pthread's
condition wait/signal.
specific privilege names to a broad range of privileges. These may
require some future tweaking.
Sponsored by: nCircle Network Security, Inc.
Obtained from: TrustedBSD Project
Discussed on: arch@
Reviewed (at least in part) by: mlaier, jmg, pjd, bde, ceri,
Alex Lyashkov <umka at sevcity dot net>,
Skip Ford <skip dot ford at verizon dot net>,
Antoine Brodin <antoine dot brodin at laposte dot net>
calls are not used by libthr in RELENG_6 and HEAD, it is only used by
the libthr in RELENG-5, the _umtx_op system call can do more incremental
dirty works than these two system calls without having to introduce new
system calls or throw away old system calls when things are going on.
