238 lines
7.4 KiB
Groff
238 lines
7.4 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93
|
|
.\"
|
|
.Dd September 30, 2016
|
|
.Dt GETRLIMIT 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm getrlimit ,
|
|
.Nm setrlimit
|
|
.Nd control maximum system resource consumption
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In sys/types.h
|
|
.In sys/time.h
|
|
.In sys/resource.h
|
|
.Ft int
|
|
.Fn getrlimit "int resource" "struct rlimit *rlp"
|
|
.Ft int
|
|
.Fn setrlimit "int resource" "const struct rlimit *rlp"
|
|
.Sh DESCRIPTION
|
|
Limits on the consumption of system resources by the current process
|
|
and each process it creates may be obtained with the
|
|
.Fn getrlimit
|
|
system call, and set with the
|
|
.Fn setrlimit
|
|
system call.
|
|
.Pp
|
|
The
|
|
.Fa resource
|
|
argument is one of the following:
|
|
.Bl -tag -width RLIMIT_FSIZEAA
|
|
.It Dv RLIMIT_AS
|
|
The maximum amount (in bytes) of virtual memory the process is
|
|
allowed to map.
|
|
.It Dv RLIMIT_CORE
|
|
The largest size (in bytes)
|
|
.Xr core 5
|
|
file that may be created.
|
|
.It Dv RLIMIT_CPU
|
|
The maximum amount of cpu time (in seconds) to be used by
|
|
each process.
|
|
.It Dv RLIMIT_DATA
|
|
The maximum size (in bytes) of the data segment for a process;
|
|
this defines how far a program may extend its break with the
|
|
.Xr sbrk 2
|
|
function.
|
|
.It Dv RLIMIT_FSIZE
|
|
The largest size (in bytes) file that may be created.
|
|
.It Dv RLIMIT_KQUEUES
|
|
The maximum number of kqueues this user id is allowed to create.
|
|
.It Dv RLIMIT_MEMLOCK
|
|
The maximum size (in bytes) which a process may lock into memory
|
|
using the
|
|
.Xr mlock 2
|
|
system call.
|
|
.It Dv RLIMIT_NOFILE
|
|
The maximum number of open files for this process.
|
|
.It Dv RLIMIT_NPROC
|
|
The maximum number of simultaneous processes for this user id.
|
|
.It Dv RLIMIT_NPTS
|
|
The maximum number of pseudo-terminals this user id is allowed to create.
|
|
.It Dv RLIMIT_RSS
|
|
When there is memory pressure and swap is available, prioritize eviction of
|
|
a process' resident pages beyond this amount (in bytes).
|
|
When memory is not under pressure, this rlimit is effectively ignored.
|
|
Even when there is memory pressure, the amount of available swap space and some
|
|
sysctl settings like
|
|
.Xr vm.swap_enabled
|
|
and
|
|
.Xr vm.swap_idle_enabled
|
|
can affect what happens to processes that have exceeded this size.
|
|
.Pp
|
|
Processes that exceed their set
|
|
.Dv RLIMIT_RSS
|
|
are not signalled or halted.
|
|
The limit is merely a hint to the VM daemon to prefer to deactivate pages from
|
|
processes that have exceeded their set
|
|
.Dv RLIMIT_RSS .
|
|
.It Dv RLIMIT_SBSIZE
|
|
The maximum size (in bytes) of socket buffer usage for this user.
|
|
This limits the amount of network memory, and hence the amount of
|
|
mbufs, that this user may hold at any time.
|
|
.It Dv RLIMIT_STACK
|
|
The maximum size (in bytes) of the stack segment for a process;
|
|
this defines how far a program's stack segment may be extended.
|
|
Stack extension is performed automatically by the system.
|
|
.It Dv RLIMIT_SWAP
|
|
The maximum size (in bytes) of the swap space that may be reserved or
|
|
used by all of this user id's processes.
|
|
This limit is enforced only if bit 1 of the
|
|
.Va vm.overcommit
|
|
sysctl is set.
|
|
Please see
|
|
.Xr tuning 7
|
|
for a complete description of this sysctl.
|
|
.It Dv RLIMIT_VMEM
|
|
An alias for
|
|
.Dv RLIMIT_AS .
|
|
.El
|
|
.Pp
|
|
A resource limit is specified as a soft limit and a hard limit.
|
|
When a soft limit is exceeded, a process might or might not receive a signal.
|
|
For example, signals are generated when the cpu time or file size is exceeded,
|
|
but not if the address space or RSS limit is exceeded.
|
|
A program that exceeds the soft limit is allowed to continue execution until it
|
|
reaches the hard limit, or modifies its own resource limit.
|
|
Even reaching the hard limit does not necessarily halt a process.
|
|
For example, if the RSS hard limit is exceeded, nothing happens.
|
|
.Pp
|
|
The
|
|
.Vt rlimit
|
|
structure is used to specify the hard and soft limits on a resource.
|
|
.Bd -literal -offset indent
|
|
struct rlimit {
|
|
rlim_t rlim_cur; /* current (soft) limit */
|
|
rlim_t rlim_max; /* maximum value for rlim_cur */
|
|
};
|
|
.Ed
|
|
.Pp
|
|
Only the super-user may raise the maximum limits.
|
|
Other users
|
|
may only alter
|
|
.Fa rlim_cur
|
|
within the range from 0 to
|
|
.Fa rlim_max
|
|
or (irreversibly) lower
|
|
.Fa rlim_max .
|
|
.Pp
|
|
An
|
|
.Dq infinite
|
|
value for a limit is defined as
|
|
.Dv RLIM_INFINITY .
|
|
.Pp
|
|
Because this information is stored in the per-process information,
|
|
this system call must be executed directly by the shell if it
|
|
is to affect all future processes created by the shell;
|
|
.Ic limit
|
|
is thus a built-in command to
|
|
.Xr csh 1 .
|
|
.Pp
|
|
The system refuses to extend the data or stack space when the limits
|
|
would be exceeded in the normal way: a
|
|
.Xr brk 2
|
|
function fails if the data space limit is reached.
|
|
When the stack limit is reached, the process receives
|
|
a segmentation fault
|
|
.Pq Dv SIGSEGV ;
|
|
if this signal is not
|
|
caught by a handler using the signal stack, this signal
|
|
will kill the process.
|
|
.Pp
|
|
A file I/O operation that would create a file larger that the process'
|
|
soft limit will cause the write to fail and a signal
|
|
.Dv SIGXFSZ
|
|
to be
|
|
generated; this normally terminates the process, but may be caught.
|
|
When
|
|
the soft cpu time limit is exceeded, a
|
|
.Dv SIGXCPU
|
|
signal is sent to the
|
|
offending process.
|
|
.Pp
|
|
When most operations would allocate more virtual memory than allowed by the
|
|
soft limit of
|
|
.Dv RLIMIT_AS ,
|
|
the operation fails with
|
|
.Dv ENOMEM
|
|
and no signal is raised.
|
|
A notable exception is stack extension, described above.
|
|
If stack extension would allocate more virtual memory than allowed by the soft
|
|
limit of
|
|
.Dv RLIMIT_AS ,
|
|
a
|
|
.Dv SIGSEGV
|
|
signal will be delivered.
|
|
The caller is free to raise the soft address space limit up to the hard limit
|
|
and retry the allocation.
|
|
.Sh RETURN VALUES
|
|
.Rv -std
|
|
.Sh ERRORS
|
|
The
|
|
.Fn getrlimit
|
|
and
|
|
.Fn setrlimit
|
|
system calls
|
|
will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EFAULT
|
|
The address specified for
|
|
.Fa rlp
|
|
is invalid.
|
|
.It Bq Er EPERM
|
|
The limit specified to
|
|
.Fn setrlimit
|
|
would have
|
|
raised the maximum limit value, and the caller is not the super-user.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr csh 1 ,
|
|
.Xr quota 1 ,
|
|
.Xr quotactl 2 ,
|
|
.Xr sigaction 2 ,
|
|
.Xr sigaltstack 2 ,
|
|
.Xr sysctl 3 ,
|
|
.Xr ulimit 3
|
|
.Sh HISTORY
|
|
The
|
|
.Fn getrlimit
|
|
system call appeared in
|
|
.Bx 4.2 .
|