memtester(8) Maintenance Commands memtester(8)
NAME
memtester - stress test to find memory subsystem faults.
SYNOPSIS
memtester [-p PHYSADDR [-d DEVICE]] <MEMORY> [ITERATIONS]
DESCRIPTION
memtester is an effective userspace tester for stress-testing the mem-
ory subsystem. It is very effective at finding intermittent and non-
deterministic faults. Note that problems in other hardware areas
(overheating CPU, out-of-specification power supply, etc.) can cause
intermittent memory faults, so it is still up to you to determine where
the fault lies through normal hardware diagnostic procedures; memtester
just helps you determine whether a problem exists.
memtester will malloc(3) the amount of memory specified, if possible.
If this fails, it will decrease the amount of memory requested until it
succeeds. It will then attempt to mlock(3) this memory; if it cannot
do so, testing will be slower and much less effective. Run memtester
as root so that it can mlock the memory it tests.
Note that the maximum amount of memory that memtester can test will be
less than the total amount of memory installed in the system; the oper-
ating system, libraries, and other system limits take some of the
available memory. memtester is also limited to the amount of memory
available to a single process; for example, on 32-bit machines with
more than 4GB of memory, memtester is still limited to less than 4GB.
Note that it is up to you to know how much memory you can safely allo-
cate for testing. If you attempt to allocate more memory than is
available, memtester should figure that out, reduce the amount
slightly, and try again. However, this can lead to memtester success-
fully allocating and mlocking essentially all free memory on the system
-- if other programs are running, this can lead to excessive swapping
and slowing the system down to the point that it is difficult to use.
If the system allows allocation of more memory than is actually avail-
able (overcommit), it may lead to a deadlock, where the system halts.
If the system has an out-of-memory process killer (like Linux),
memtester or another process may be killed by the OOM killer.
So choose wisely.
OPTIONS
-p PHYSADDR
tells memtester to test a specific region of memory starting at
physical address PHYSADDR (given in hex), by mmap(2)ing a device
specified by the -d option (below, or /dev/mem by default).
This is mostly of use to hardware developers, for testing mem-
ory-mapped I/O devices and similar. Note that the memory region
will be overwritten during testing, so it is not safe to specify
memory which is allocated for the system or for other applica-
tions; doing so will cause them to crash. If you absolutely
must test a particular region of actual physical memory, arrange
to have that memory allocated by your test software, and hold it
in this allocated state, then run memtester on it with this op-
tion.
MEMORY the amount of memory to allocate and test, in megabytes by de-
fault. You can include a suffix of B, K, M, or G to indicate
bytes, kilobytes, megabytes, or gigabytes respectively.
ITERATIONS
(optional) number of loops to iterate through. Default is infi-
nite.
ENVIRONMENT
If the environment variable MEMTESTER_TEST_MASK is set, memtester
treats the value as a bitmask of which tests (other than the stuck ad-
dress test) to run. The value can be specified in decimal, in octal
(with a leading 0), or in hexadecimal (with a leading 0x). The spe-
cific bit values corresponding to particular tests may change from re-
lease to release; consult the list of tests in the source for the ap-
propriate index values for the version of memtester you are running.
Note that skipping some tests will reduce the time it takes for
memtester to run, but also reduce memtester's effectiveness.
NOTE
memtester must be run with root privileges to mlock(3) its pages.
Testing memory without locking the pages in place is mostly pointless
and slow.
EXIT CODE
memtester's exit code is 0 when everything works properly. Otherwise,
it is the logical OR of the following values:
x01 error allocating or locking memory, or invocation error
x02 error during stuck address test
x04 error during one of the other tests
AUTHOR
Written by Charles Cazabon.
REPORTING BUGS
Report bugs to <charlesc-memtester-bugs@pyropus.ca>.
COPYRIGHT
Copyright © 2001-2020 Charles Cazabon
This is free software; see the file COPYING for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
memtester 4 September 2020 memtester(8)
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