routine wakes up proc0 so that proc0 can swap the thread back in.
Historically, this has been done by waking up proc0 directly from
setrunnable() itself via a wakeup(). When waking up a sleeping thread
that was swapped out (the usual case when waking proc0 since only sleeping
threads are eligible to be swapped out), this resulted in a bit of
recursion (e.g. wakeup() -> setrunnable() -> wakeup()).
With sleep queues having separate locks in 6.x and later, this caused a
spin lock LOR (sleepq lock -> sched_lock/thread lock -> sleepq lock).
An attempt was made to fix this in 7.0 by making the proc0 wakeup use
the ithread mechanism for doing the wakeup. However, this required
grabbing proc0's thread lock to perform the wakeup. If proc0 was asleep
elsewhere in the kernel (e.g. waiting for disk I/O), then this degenerated
into the same LOR since the thread lock would be some other sleepq lock.
Fix this by deferring the wakeup of the swapper until after the sleepq
lock held by the upper layer has been locked. The setrunnable() routine
now returns a boolean value to indicate whether or not proc0 needs to be
woken up. The end result is that consumers of the sleepq API such as
*sleep/wakeup, condition variables, sx locks, and lockmgr, have to wakeup
proc0 if they get a non-zero return value from sleepq_abort(),
sleepq_broadcast(), or sleepq_signal().
Discussed with: jeff
Glanced at by: sam
Tested by: Jurgen Weber jurgen - ish com au
MFC after: 2 weeks
variables and sysctl nodes.
- In reset walk the children of kern_sched_stats and reset the counters
via the oid_arg1 pointer. This allows us to add arbitrary counters to
the tree and still reset them properly.
- Define a set of switch types to be passed with flags to mi_switch().
These types are named SWT_*. These types correspond to SCHED_STATS
counters and are automatically handled in this way.
- Make the new SWT_ types more specific than the older switch stats.
There are now stats for idle switches, remote idle wakeups, remote
preemption ithreads idling, etc.
- Add switch statistics for ULE's pickcpu algorithm. These stats include
how much migration there is, how often affinity was successful, how
often threads were migrated to the local cpu on wakeup, etc.
Sponsored by: Nokia
requiring the per-process spinlock to only requiring the process lock.
- Reflect these changes in the proc.h documentation and consumers throughout
the kernel. This is a substantial reduction in locking cost for these
fields and was made possible by recent changes to threading support.
after each SYSINIT() macro invocation. This makes a number of
lightweight C parsers much happier with the FreeBSD kernel
source, including cflow's prcc and lxr.
MFC after: 1 month
Discussed with: imp, rink
While the KSE project was quite successful in bringing threading to
FreeBSD, the M:N approach taken by the kse library was never developed
to its full potential. Backwards compatibility will be provided via
libmap.conf for dynamically linked binaries and static binaries will
be broken.
sched_sleep(). This removes extra thread_lock() acquisition and
allows the scheduler to decide what to do with the static boost.
- Change the priority arguments to cv_* to match sleepq/msleep/etc.
where 0 means no priority change. Catch -1 in cv_broadcastpri() and
convert it to 0 for now.
- Set a flag when sleeping in a way that is compatible with swapping
since direct priority comparisons are meaningless now.
- Add a sysctl to ule, kern.sched.static_boost, that defaults to on which
controls the boost behavior. Turning it off gives better performance
in some workloads but needs more investigation.
- While we're modifying sleepq, change signal and broadcast to both
return with the lock held as the lock was held on enter.
Reviewed by: jhb, peter
silent NULL pointer dereference in the i386 and sparc64 pmap_pinit()
when the kmem_alloc_nofault() failed to allocate address space. Both
functions now return error instead of panicing or dereferencing NULL.
As consequence, vmspace_exec() and vmspace_unshare() returns the errno
int. struct vmspace arg was added to vm_forkproc() to avoid dealing
with failed allocation when most of the fork1() job is already done.
The kernel stack for the thread is now set up in the thread_alloc(),
that itself may return NULL. Also, allocation of the first process
thread is performed in the fork1() to properly deal with stack
allocation failure. proc_linkup() is separated into proc_linkup()
called from fork1(), and proc_linkup0(), that is used to set up the
kernel process (was known as swapper).
In collaboration with: Peter Holm
Reviewed by: jhb
changes the units from seconds to the value of 'ticks' when swapped
in/out. ULE does not have a periodic timer that scans all threads in
the system and as such maintaining a per-second counter is difficult.
- Change computations requiring the unit in seconds to subtract ticks
and divide by hz. This does make the wraparound condition hz times
more frequent but this is still in the range of several months to
years and the adverse effects are minimal.
Approved by: re
- p_sflag was mostly protected by PROC_LOCK rather than the PROC_SLOCK or
previously the sched_lock. These bugs have existed for some time.
- Allow swapout to try each thread in a process individually and then
swapin the whole process if any of these fail. This allows us to move
most scheduler related swap flags into td_flags.
- Keep ki_sflag for backwards compat but change all in source tools to
use the new and more correct location of P_INMEM.
Reported by: pho
Reviewed by: attilio, kib
Approved by: re (kensmith)
- Use thread_lock() rather than sched_lock for per-thread scheduling
sychronization.
- Use the per-process spinlock rather than the sched_lock for per-process
scheduling synchronization.
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)
td_ru. This removes the requirement for per-process synchronization in
statclock() and mi_switch(). This was previously supported by
sched_lock which is going away. All modifications to rusage are now
done in the context of the owning thread. reads proceed without locks.
- Aggregate exiting threads rusage in thread_exit() such that the exiting
thread's rusage is not lost.
- Provide a new routine, rufetch() to fetch an aggregate of all rusage
structures from all threads in a process. This routine must be used
in any place requiring a rusage from a process prior to it's exit. The
exited process's rusage is still available via p_ru.
- Aggregate tick statistics only on demand via rufetch() or when a thread
exits. Tick statistics are kept in the thread and protected by sched_lock
until it exits.
Initial patch by: attilio
Reviewed by: attilio, bde (some objections), arch (mostly silent)
Probabilly, a general approach is not the better solution here, so we should
solve the sched_lock protection problems separately.
Requested by: alc
Approved by: jeff (mentor)
vmcnts. This can be used to abstract away pcpu details but also changes
to use atomics for all counters now. This means sched lock is no longer
responsible for protecting counts in the switch routines.
Contributed by: Attilio Rao <attilio@FreeBSD.org>
setrunqueue() was mostly empty. The few asserts and thread state
setting were moved to the individual schedulers. sched_add() was
chosen to displace it for naming consistency reasons.
- Remove adjustrunqueue, it was 4 lines of code that was ifdef'd to be
different on all three schedulers where it was only called in one place
each.
- Remove the long ifdef'd out remrunqueue code.
- Remove the now redundant ts_state. Inspect the thread state directly.
- Don't set TSF_* flags from kern_switch.c, we were only doing this to
support a feature in one scheduler.
- Change sched_choose() to return a thread rather than a td_sched. Also,
rely on the schedulers to return the idlethread. This simplifies the
logic in choosethread(). Aside from the run queue links kern_switch.c
mostly does not care about the contents of td_sched.
Discussed with: julian
- Move the idle thread loop into the per scheduler area. ULE wants to
do something different from the other schedulers.
Suggested by: jhb
Tested on: x86/amd64 sched_{4BSD, ULE, CORE}.
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.
vmspace_exitfree() and vmspace_free() which could result in the same
vmspace being freed twice.
Factor out part of exit1() into new function vmspace_exit(). Attach
to vmspace0 to allow old vmspace to be freed earlier.
Add new function, vmspace_acquire_ref(), for obtaining a vmspace
reference for a vmspace belonging to another process. Avoid changing
vmspace refcount from 0 to 1 since that could also lead to the same
vmspace being freed twice.
Change vmtotal() and swapout_procs() to use vmspace_acquire_ref().
Reviewed by: alc
ephemeral mappings that are used as the source for three copy
operations from kernel space to user space. There are two reasons for
making this change: (1) Under heavy load exec_map can fill up causing
vm_map_find() to fail. When it fails, the nascent process is aborted
(SIGABRT). Whereas, this reimplementation using sf_buf_alloc()
sleeps. (2) Although it is possible to sleep on vm_map_find()'s
failure until address space becomes available (see kmem_alloc_wait()),
using sf_buf_alloc() is faster. Furthermore, the reimplementation
uses a CPU private mapping, avoiding a TLB shootdown on
multiprocessors.
Problem uncovered by: kris@
Reviewed by: tegge@
MFC after: 3 weeks
need for most calls to vm_page_busy(). Specifically, most calls to
vm_page_busy() occur immediately prior to a call to vm_page_remove().
In such cases, the containing vm object is locked across both calls.
Consequently, the setting of the vm page's PG_BUSY flag is not even
visible to other threads that are following the synchronization
protocol.
This change (1) eliminates the calls to vm_page_busy() that
immediately precede a call to vm_page_remove() or functions, such as
vm_page_free() and vm_page_rename(), that call it and (2) relaxes the
requirement in vm_page_remove() that the vm page's PG_BUSY flag is
set. Now, the vm page's PG_BUSY flag is set only when the vm object
lock is released while the vm page is still in transition. Typically,
this is when it is undergoing I/O.
UMA_ZONE_NOFREE to guarantee type stability, so proc_fini() should
never be called. Move an assertion from proc_fini() to proc_dtor()
and garbage-collect the rest of the unreachable code. I have retained
vm_proc_dispose(), since I consider its disuse a bug.
- Push down Giant into shmexit(). (Giant is acquired only if the vmspace
contains shm segments.)
- Eliminate the acquisition of Giant from proc_rwmem().
- Reduce the scope of Giant in exit1(), uncovering the destruction of the
address space.
Just use p2->p_uarea directly instead.
- Remove an old and mostly bogus assertion regarding p2->p_sigacts.
- Use RANGEOF macro ala fork1() to clean up bzero/bcopy of p_stats.
ever since alpha/alpha/pmap.c revision 1.81 introduced the list allpmaps,
there has been no reason for having this function on Alpha. Briefly,
when pmap_growkernel() relied upon the list of all processes to find and
update the various pmaps to reflect a growth in the kernel's valid
address space, pmap_init2() served to avoid a race between pmap
initialization and pmap_growkernel(). Specifically, pmap_pinit2() was
responsible for initializing the kernel portions of the pmap and
pmap_pinit2() was called after the process structure contained a pointer
to the new pmap for use by pmap_growkernel(). Thus, an update to the
kernel's address space might be applied to the new pmap unnecessarily,
but an update would never be lost.
introduction of kern_mlock() and kern_munlock() in
src/sys/kern/kern_sysctl.c 1.150
src/sys/vm/vm_extern.h 1.69
src/sys/vm/vm_glue.c 1.190
src/sys/vm/vm_mmap.c 1.179
because different resource limits are appropriate for transient and
"permanent" page wiring requests.
Retain the kern_mlock() and kern_munlock() API in the revived
vslock() and vsunlock() functions.
Combine the best parts of each of the original sets of implementations
with further code cleanup. Make the mclock() and vslock()
implementations as similar as possible.
Retain the RLIMIT_MEMLOCK check in mlock(). Move the most strigent
test, which can return EAGAIN, last so that requests that have no
hope of ever being satisfied will not be retried unnecessarily.
Disable the test that can return EAGAIN in the vslock() implementation
because it will cause the sysctl code to wedge.
Tested by: Cy Schubert <Cy.Schubert AT komquats.com>
the syscall arguments and does the suser() permission check, and
kern_mlock(), which does the resource limit checking and calls
vm_map_wire(). Split munlock() in a similar way.
Enable the RLIMIT_MEMLOCK checking code in kern_mlock().
Replace calls to vslock() and vsunlock() in the sysctl code with
calls to kern_mlock() and kern_munlock() so that the sysctl code
will obey the wired memory limits.
Nuke the vslock() and vsunlock() implementations, which are no
longer used.
Add a member to struct sysctl_req to track the amount of memory
that is wired to handle the request.
Modify sysctl_wire_old_buffer() to return an error if its call to
kern_mlock() fails. Only wire the minimum of the length specified
in the sysctl request and the length specified in its argument list.
It is recommended that sysctl handlers that use sysctl_wire_old_buffer()
should specify reasonable estimates for the amount of data they
want to return so that only the minimum amount of memory is wired
no matter what length has been specified by the request.
Modify the callers of sysctl_wire_old_buffer() to look for the
error return.
Modify sysctl_old_user to obey the wired buffer length and clean up
its implementation.
Reviewed by: bms
- struct plimit includes a mutex to protect a reference count. The plimit
structure is treated similarly to struct ucred in that is is always copy
on write, so having a reference to a structure is sufficient to read from
it without needing a further lock.
- The proc lock protects the p_limit pointer and must be held while reading
limits from a process to keep the limit structure from changing out from
under you while reading from it.
- Various global limits that are ints are not protected by a lock since
int writes are atomic on all the archs we support and thus a lock
wouldn't buy us anything.
- All accesses to individual resource limits from a process are abstracted
behind a simple lim_rlimit(), lim_max(), and lim_cur() API that return
either an rlimit, or the current or max individual limit of the specified
resource from a process.
- dosetrlimit() was renamed to kern_setrlimit() to match existing style of
other similar syscall helper functions.
- The alpha OSF/1 compat layer no longer calls getrlimit() and setrlimit()
(it didn't used the stackgap when it should have) but uses lim_rlimit()
and kern_setrlimit() instead.
- The svr4 compat no longer uses the stackgap for resource limits calls,
but uses lim_rlimit() and kern_setrlimit() instead.
- The ibcs2 compat no longer uses the stackgap for resource limits. It
also no longer uses the stackgap for accessing sysctl's for the
ibcs2_sysconf() syscall but uses kernel_sysctl() instead. As a result,
ibcs2_sysconf() no longer needs Giant.
- The p_rlimit macro no longer exists.
Submitted by: mtm (mostly, I only did a few cleanups and catchups)
Tested on: i386
Compiled on: alpha, amd64
"scheduler" here has very little to do with scheduling. It is actually
the swapper, and it really must be the last SYSINIT'ed item like its
comment says, since proc0 metamorphoses into swapper by calling
scheduler() last in mi_start(), and scheduler() never returns.. Rev.1.29
of subr_4bsd.c broke this by adding another SI_ORDER_FIRST item
(kproc_start() for schedcpu_thread() onto the SI_SUB_RUN_SCHEDULER_LIST.
The sorting of SYSINITs with identical orders (at all levels) is
apparently nondeterministic, so this resulted in schedule() sometimes
being called second last and schedcpu_thread() not being called at all.
This quick fix just changes the code to almost match the comment
(SI_ORDER_FIRST -> SI_ORDER_ANY). "LAST" is misspelled "ANY", and
there is no way to ensure that there is only 1 very lst SYSINIT.
A more complete fix would remove the SYSINIT obfuscation.
must return EINVAL if size is zero. Submitted by: tegge
- In order to avoid a race condition in multithreaded applications, the
check and removal operations by munmap(2) must be in the same critical
section. To accomodate this, vm_map_check_protection() is modified to
require its caller to obtain at least a read lock on the map.
