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The "initial_nr_hugepages" variable is unsigned long so it takes up to 20
characters to print, plus 1 more character for the NUL terminator.
Unfortunately, this buffer is not quite large enough for the terminator to
fit. Also use snprintf() for a belt and suspenders approach.
Link: https://lkml.kernel.org/r/[email protected]
Fixes: fb9293b6b015 ("selftests/mm: compaction_test: fix bogus test success and reduce probability of OOM-killer invocation")
Signed-off-by: Dan Carpenter <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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of OOM-killer invocation
Reset nr_hugepages to zero before the start of the test.
If a non-zero number of hugepages is already set before the start of the
test, the following problems arise:
- The probability of the test getting OOM-killed increases. Proof:
The test wants to run on 80% of available memory to prevent OOM-killing
(see original code comments). Let the value of mem_free at the start
of the test, when nr_hugepages = 0, be x. In the other case, when
nr_hugepages > 0, let the memory consumed by hugepages be y. In the
former case, the test operates on 0.8 * x of memory. In the latter,
the test operates on 0.8 * (x - y) of memory, with y already filled,
hence, memory consumed is y + 0.8 * (x - y) = 0.8 * x + 0.2 * y > 0.8 *
x. Q.E.D
- The probability of a bogus test success increases. Proof: Let the
memory consumed by hugepages be greater than 25% of x, with x and y
defined as above. The definition of compaction_index is c_index = (x -
y)/z where z is the memory consumed by hugepages after trying to
increase them again. In check_compaction(), we set the number of
hugepages to zero, and then increase them back; the probability that
they will be set back to consume at least y amount of memory again is
very high (since there is not much delay between the two attempts of
changing nr_hugepages). Hence, z >= y > (x/4) (by the 25% assumption).
Therefore, c_index = (x - y)/z <= (x - y)/y = x/y - 1 < 4 - 1 = 3
hence, c_index can always be forced to be less than 3, thereby the test
succeeding always. Q.E.D
Link: https://lkml.kernel.org/r/[email protected]
Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory")
Signed-off-by: Dev Jain <[email protected]>
Cc: <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Sri Jayaramappa <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Currently, the test tries to set nr_hugepages to zero, but that is not
actually done because the file offset is not reset after read(). Fix that
using lseek().
Link: https://lkml.kernel.org/r/[email protected]
Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory")
Signed-off-by: Dev Jain <[email protected]>
Cc: <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Sri Jayaramappa <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Patch series "Fixes for compaction_test", v2.
The compaction_test memory selftest introduces fragmentation in memory
and then tries to allocate as many hugepages as possible. This series
addresses some problems.
On Aarch64, if nr_hugepages == 0, then the test trivially succeeds since
compaction_index becomes 0, which is less than 3, due to no division by
zero exception being raised. We fix that by checking for division by
zero.
Secondly, correctly set the number of hugepages to zero before trying
to set a large number of them.
Now, consider a situation in which, at the start of the test, a non-zero
number of hugepages have been already set (while running the entire
selftests/mm suite, or manually by the admin). The test operates on 80%
of memory to avoid OOM-killer invocation, and because some memory is
already blocked by hugepages, it would increase the chance of OOM-killing.
Also, since mem_free used in check_compaction() is the value before we
set nr_hugepages to zero, the chance that the compaction_index will
be small is very high if the preset nr_hugepages was high, leading to a
bogus test success.
This patch (of 3):
Currently, if at runtime we are not able to allocate a huge page, the test
will trivially pass on Aarch64 due to no exception being raised on
division by zero while computing compaction_index. Fix that by checking
for nr_hugepages == 0. Anyways, in general, avoid a division by zero by
exiting the program beforehand. While at it, fix a typo, and handle the
case where the number of hugepages may overflow an integer.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Fixes: bd67d5c15cc1 ("Test compaction of mlocked memory")
Signed-off-by: Dev Jain <[email protected]>
Cc: Anshuman Khandual <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Sri Jayaramappa <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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After commit f7d5bcd35d42 ("selftests: kselftest: Mark functions that
unconditionally call exit() as __noreturn"), ksft_exit_...() functions
are marked as __noreturn, which means the return type should not be
'int' but 'void' because they are not returning anything (and never were
since exit() has always been called).
To facilitate updating the return type of these functions, remove
'return' before the calls to ksft_exit_...(), as __noreturn prevents the
compiler from warning that a caller of the ksft_exit functions does not
return a value because the program will terminate upon calling these
functions.
Reviewed-by: Muhammad Usama Anjum <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>
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Every test result report in the compaction test prints a distinct log
messae, and some of the reports print a name that varies at runtime. This
causes problems for automation since a lot of automation software uses the
printed string as the name of the test, if the name varies from run to run
and from pass to fail then the automation software can't identify that a
test changed result or that the same tests are being run.
Refactor the logging to use a consistent name when printing the result of
the test, printing the existing messages as diagnostic information instead
so they are still available for people trying to interpret the results.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>
Cc: Muhammad Usama Anjum <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Patch series "selftests/mm: Output cleanups for the compaction test".
A couple of small updates for the check_compaction selftest which make
it play more nicely with test automation systems.
This patch (of 2):
When the compaction test is run it checks to make sure that prerequistives
the test requires are available and skips the tests if not. When this
happens we log the test as a pass rather than a skip, log as a skip so
that the distinction is clear and automation can see unexpected skips.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>
Cc: Muhammad Usama Anjum <[email protected]>
Cc: Ryan Roberts <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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The test depends on writing to nr_hugepages which isn't possible without
root privileges. So skip the test in this case.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Muhammad Usama Anjum <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Conform the layout, informational and status messages to TAP. No
functional change is intended other than the layout of output messages.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Muhammad Usama Anjum <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Rename selftets/vm to selftests/mm for being more consistent with the
code, documentation, and tools directories, and won't be confused with
virtual machines.
[[email protected]: convert missing vm->mm changes]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: SeongJae Park <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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