1memtester(8) Maintenance Commands memtester(8)
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6 memtester - stress test to find memory subsystem faults.
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9 memtester [-p PHYSADDR [-d DEVICE]] <MEMORY> [ITERATIONS]
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12 memtester is an effective userspace tester for stress-testing the mem‐
13 ory subsystem. It is very effective at finding intermittent and non-
14 deterministic faults. Note that problems in other hardware areas
15 (overheating CPU, out-of-specification power supply, etc.) can cause
16 intermittent memory faults, so it is still up to you to determine where
17 the fault lies through normal hardware diagnostic procedures; memtester
18 just helps you determine whether a problem exists.
19 memtester will malloc(3) the amount of memory specified, if possible.
21 If this fails, it will decrease the amount of memory requested until it
22 succeeds. It will then attempt to mlock(3) this memory; if it cannot
23 do so, testing will be slower and much less effective. Run memtester
24 as root so that it can mlock the memory it tests.
25 Note that the maximum amount of memory that memtester can test will be
27 less than the total amount of memory installed in the system; the oper‐
28 ating system, libraries, and other system limits take some of the
29 available memory. memtester is also limited to the amount of memory
30 available to a single process; for example, on 32-bit machines with
31 more than 4GB of memory, memtester is still limited to less than 4GB.
32 Note that it is up to you to know how much memory you can safely allo‐
34 cate for testing. If you attempt to allocate more memory than is
35 available, memtester should figure that out, reduce the amount
36 slightly, and try again. However, this can lead to memtester success‐
37 fully allocating and mlocking essentially all free memory on the system
38 -- if other programs are running, this can lead to excessive swapping
39 and slowing the system down to the point that it is difficult to use.
40 If the system allows allocation of more memory than is actually avail‐
41 able (overcommit), it may lead to a deadlock, where the system halts.
42 If the system has an out-of-memory process killer (like Linux),
43 memtester or another process may be killed by the OOM killer.
44 So choose wisely.
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48 -p PHYSADDR
49 tells memtester to test a specific region of memory starting at
50 physical address PHYSADDR (given in hex), by mmap(2)ing a device
51 specified by the -d option (below, or /dev/mem by default).
52 This is mostly of use to hardware developers, for testing mem‐
53 ory-mapped I/O devices and similar. Note that the memory region
54 will be overwritten during testing, so it is not safe to specify
55 memory which is allocated for the system or for other applica‐
56 tions; doing so will cause them to crash. If you absolutely
57 must test a particular region of actual physical memory, arrange
58 to have that memory allocated by your test software, and hold it
59 in this allocated state, then run memtester on it with this
60 option.
61 MEMORY the amount of memory to allocate and test, in megabytes by
63 default. You can include a suffix of B, K, M, or G to indicate
64 bytes, kilobytes, megabytes, or gigabytes respectively.
65 ITERATIONS
67 (optional) number of loops to iterate through. Default is infi‐
68 nite.
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71 If the environment variable MEMTESTER_TEST_MASK is set, memtester
72 treats the value as a bitmask of which tests (other than the stuck
73 address test) to run. The value can be specified in decimal, in octal
74 (with a leading 0), or in hexadecimal (with a leading 0x). The spe‐
75 cific bit values corresponding to particular tests may change from
76 release to release; consult the list of tests in the source for the
77 appropriate index values for the version of memtester you are running.
78 Note that skipping some tests will reduce the time it takes for
79 memtester to run, but also reduce memtester's effectiveness.
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82 memtester must be run with root privileges to mlock(3) its pages.
83 Testing memory without locking the pages in place is mostly pointless
84 and slow.
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87 memtester's exit code is 0 when everything works properly. Otherwise,
88 it is the logical OR of the following values:
89 x01 error allocating or locking memory, or invocation error
91 x02 error during stuck address test
93 x04 error during one of the other tests
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97 Written by Charles Cazabon.
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100 Report bugs to <charlesc-memtester-bugs@pyropus.ca>.
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103 Copyright © 2001-2012 Charles Cazabon
104 This is free software; see the file COPYING for copying conditions.
105 There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
106 PARTICULAR PURPOSE.
107memtester 4 June 2012 memtester(8)