defaults to 1, meaning that it's off.
When read-ahead is enabled on a file, the vfs cluster code deliberately
breaks a read into 2 I/O transactions; one to satisfy the actual read,
and one to perform read-ahead. This makes sense in low-latency
circumstances, but often produces unbalanced i/o transactions that
penalize disks. By setting vfs.read_min, we can tell the algorithm to
fetch a larger transaction that what we asked for, achieving the same
effect as the read-ahead but without the doubled, unbalanced transaction
and the slightly lower latency. This significantly helps our workloads
with video streaming.
Submitted by: emax
Reviewed by: kib
Obtained from: Netflix
kernel-based POSIX semaphore descriptors to userland via procstat(1) and
fstat(1):
- Change sem file descriptors to track the pathname they are associated
with and add a ksem_info() method to copy the path out to a
caller-supplied buffer.
- Use the fo_stat() method of shared memory objects and ksem_info() to
export the path, mode, and value of a semaphore via struct kinfo_file.
- Add a struct semstat to the libprocstat(3) interface along with a
procstat_get_sem_info() to export the mode and value of a semaphore.
- Teach fstat about semaphores and to display their path, mode, and value.
MFC after: 2 weeks
it was being passed down to VOP_IOCTL() where it promptly resulted in
ENOTTY due to a missing else for the past 8 years. While here, use a
shared vnode lock while fetching the current file's size.
MFC after: 1 week
The pipe2() function is similar to pipe() but allows setting FD_CLOEXEC and
O_NONBLOCK (on both sides) as part of the function.
If p points to two writable ints, pipe2(p, 0) is equivalent to pipe(p).
If the pointer is not valid, behaviour differs: pipe2() writes into the
array from the kernel like socketpair() does, while pipe() writes into the
array from an architecture-specific assembler wrapper.
Reviewed by: kan, kib
The accept4() function, compared to accept(), allows setting the new file
descriptor atomically close-on-exec and explicitly controlling the
non-blocking status on the new socket. (Note that the latter point means
that accept() is not equivalent to any form of accept4().)
The linuxulator's accept4 implementation leaves a race window where the new
file descriptor is not close-on-exec because it calls sys_accept(). This
implementation leaves no such race window (by using falloc() flags). The
linuxulator could be fixed and simplified by using the new code.
Like accept(), accept4() is async-signal-safe, a cancellation point and
permitted in capability mode.
A blocking accept (and some other operations) waits on &so->so_timeo. Once
it wakes up, it will detect the SBS_CANTRCVMORE bit.
The error from accept() is [ECONNABORTED] which is not the nicest one -- the
thread calling accept() needs to know out-of-band what is happening.
A spurious wakeup on so->so_timeo appears harmless (sleep retried) except
when lingering on close (SO_LINGER, and in that case there is no descriptor
to call shutdown() on) so this should be fairly safe.
A shutdown() already woke up a blocked accept() for TCP sockets, but not for
Unix domain sockets. This fix is generic for all domains.
This patch was sent to -hackers@ and -net@ on April 5.
MFC after: 2 weeks
the file size, use VOP_GETATTR() instead of accessing vnode vm_object
un_pager.vnp.vnp_size.
Take the shared vnode lock earlier to cover the added VOP_GETATTR()
call and, as consequence, the whole internal sendfile loop. Reduce vm
object lock scope to not protect the local calculations.
Note that this is the last misuse of the vnp_size in the tree, the
others were removed from the ELF image activator by r230246.
Reviewed by: alc
Tested by: pho, bf (previous version)
MFC after: 1 week
instead of kernel_map size to prevent kernel memory exhaustion
by mbufs and a subsequent panic on physical page allocation
failure.
On architectures without a direct map all mbuf memory (except
for jumbo mbufs larger than PAGE_SIZE) comes from kmem_map.
It is the limiting factor hence.
For architectures with a direct map using the size of kmem_map
is a good proxy of available kernel memory as well. If it is
much smaller the mbuf limit may be sub-optimal but remains
reasonable, while avoiding panics under exhaustion.
The overall mbuf memory limit calculation may be reconsidered
again later, however due to the many different mbuf sizes and
different backing KVM maps it is a tricky subject.
Found by: pho's new network stress test
Pointed out by: alc (kmem_map instead of kernel_map)
Tested by: pho
Programs often do not expect an [EINTR] return from sem_wait() and POSIX
only allows it if the signal was installed without SA_RESTART. The timeout
in sem_timedwait() is absolute so it can be restarted normally.
The umtx call can be invoked with a relative timeout and in that case
[ERESTART] must be changed to [EINTR]. However, libc does not do this.
The old POSIX semaphore implementation did this correctly (before r249566),
unlike the new umtx one.
It may be desirable to avoid [EINTR] completely, which matches the pthread
functions and is explicitly permitted by POSIX. However, the kernel must
return [EINTR] at least for signals with SA_RESTART clear, otherwise pthread
cancellation will not abort a semaphore wait. In this commit, only restore
the 8.x behaviour which is also permitted by POSIX.
Discussed with: jhb
MFC after: 1 week
prevents us from creating UMA_ZONE_PCPU zones earlier.
As bandaid shift initialization of counter(9) zone later.
Reviewed by: kib
Reported & tested by: Lytochkin Boris <lytboris gmail.com>
signal.
- Fix the old ksem implementation for POSIX semaphores to not restart
sem_wait() or sem_timedwait() if interrupted by a signal.
MFC after: 1 week
The notes format is a header of sizeof(int), which stores the size of
the corresponding data structure to provide some versioning, and data
in the format as it is returned by a related sysctl call.
The userland tools (procstat(1)) will be taught to extract this data,
providing additional info for postmortem analysis.
PR: kern/173723
Suggested by: jhb
Discussed with: jhb, kib
Reviewed by: jhb (initial version), kib
MFC after: 1 month
LK_EXCLOTHER. LK_EXCLOTHER is only used to acquire a
usecount on a vnode during NFSv4 recovery from an
expired lease.
Reported and tested by: pho
MFC after: 2 weeks
is starting. This is in line with practice in OpenSolaris.
Note that this change is only in ULE and not in the 4BSD scheduler.
Once this change settles in (MFC timeout has expired) we'll try it out
on 4BSD as well.
PR: 177706
Submitted by: Tiwei Bie
MFC after: 1 month
and kern_proc_vmmap_out() functions to output process kinfo structures
to sbuf, to make the code reusable.
The functions are going to be used in the coredump routine to store
procstat info in the core program header notes.
Reviewed by: kib
MFC after: 3 weeks
function is provided, which is used either to calculate the note size
or output it to sbuf. On the first pass the notes are registered in a
list and the resulting size is found, on the second pass the list is
traversed outputing notes to sbuf. For the sbuf a drain routine is
provided that writes data to a core file.
The main goal of the change is to make coredump to write notes
directly to the core file, without preliminary preparing them all in a
memory buffer. Storing notes in memory is not a problem for the
current, rather small, set of notes we write to the core, but it may
becomes an issue when we start to store procstat notes.
Reviewed by: jhb (initial version), kib
Discussed with: jhb, kib
MFC after: 3 weeks
In some cases, kern_envp is set by the architecture code and env_pos does
not contain the length of the static kernel environment. In these cases
r249408 causes the kernel to discard the environment.
Fix this by updating the check for empty static env to *kern_envp != '\0'
Reported by: np@
In case where there are no static kernel environment entries, the
function init_dynamic_kenv() adds an incorrect entry at position 0 of
the dynamic kernel environment. This in turn causes kenv(1) to print
and empty list even though there are dynamic entries added later.
Fix this by checking env_pos in init_dynamic_kenv() and adding dynamic
entries only if there are static entries.
reside on their own cache line to prevent false sharing with other
nearby structures, especially for those in the .bss segment.
NB: Those mutexes and rwlocks with variables next to them that get
changed on every invocation do not benefit from their own cache line.
Actually it may be net negative because two cache misses would be
incurred in those cases.
Introduce counter(9) API, that implements fast and raceless counters,
provided (but not limited to) for gathering of statistical data.
See http://lists.freebsd.org/pipermail/freebsd-arch/2013-April/014204.html
for more details.
In collaboration with: kib
Reviewed by: luigi
Tested by: ae, ray
Sponsored by: Nginx, Inc.
Although native word padding (i.e. 8-byte on 64bit arch) looks to be
in agreement with standards, other parts of our code and other OSes
use 4-byte alignment.
This is not expected to change alignment for currently generated core
dump notes, as the notes look to consist of structures with sizes
multiple of 8 on 64-bit archs. But there are plans to add additional
notes, where 4-byte vs 8-byte alignment makes difference.
Discussed with: kib
Reviewed by: kib
MFC after: 2 weeks
POSIX mqueue, compatibility ksem and POSIX shm create a file descriptor that
has close-on-exec set. However, they do this incorrectly, leaving a window
where a thread may fork and exec while the flag has not been set yet. The
race is easily reproduced on a multicore system with one thread doing
shm_open and close and another thread doing posix_spawnp and waitpid.
Set UF_EXCLOSE via falloc()'s flags argument instead. This also simplifies
the code.
MFC after: 1 week
- Don't insert BKGRDMARKER bufs into the splay or dirty/clean buf lists.
No consumers need to find them there and it complicates the tree.
These flags are all FFS specific and could be moved out of the buf
cache.
- Use pbgetvp() and pbrelvp() to associate the background and journal
bufs with the vp. Not only is this much cheaper it makes more sense
for these transient bufs.
- Fix the assertions in pbget* and pbrel*. It's not safe to check list
pointers which were never initialized. Use the BX flags instead. We
also check B_PAGING in reassignbuf() so this should cover all cases.
Discussed with: kib, mckusick, attilio
Sponsored by: EMC / Isilon Storage Division
the handler address. Add a mark to distinguish between filter and
handler.
Note that the arguments for both filter and handler are same.
Sponsored by: The FreeBSD Foundation
Reviewed by: jhb
MFC after: 1 week
Allow boothowto and bootverbose to be set via kernel options, which
is useful on architectures that are unable to rely on a boot loader
to pass configuration variables to the kernel.
Submitted by: rwatson
extattr_set_{fd,file,link} is logically a write(2)-like operation and
should return ssize_t, just like extattr_get_*. Also, the user-space
utility was using an int for the return value of extattr_get_* and
extattr_list_*, both of which return an ssize_t.
MFC after: 1 week
vnode could be reclaimed while lock upgrade was performed.
Sponsored by: The FreeBSD Foundation
Reported and tested by: pho
Diagnosed and reviewed by: rmacklem
MFC after: 1 week
