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<div class="moz-cite-prefix">On 01/04/26 20:22, Sayali Patil wrote:<br>
</div>
<blockquote type="cite"
cite="mid:2f5da9dd-812e-4645-8340-de8c6beec584@linux.ibm.com">
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On 27/03/26 12: 45, Sayali Patil wrote: During cleanup, the
value of /proc/sys/vm/nr_hugepages is currently being set to 0.
At the end of the test, if all tests pass, the original
nr_hugepages value is restored. However, if any test fails, it</div>
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<div class="moz-cite-prefix">On 27/03/26 12:45, Sayali Patil
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:2ba0f8d8a00fd049e8ed4b97e9ce8ee6b58a2892.1774591179.git.sayalip@linux.ibm.com">
<pre wrap="" class="moz-quote-pre">During cleanup, the value of /proc/sys/vm/nr_hugepages is currently being
set to 0. At the end of the test, if all tests pass, the original
nr_hugepages value is restored. However, if any test fails, it remains
set to 0.
With this patch, we ensure that the original nr_hugepages value is
restored during cleanup, regardless of whether the test passes or fails.
Fixes: 7d695b1c3695b ("selftests/mm: save and restore nr_hugepages value")
Reviewed-by: Zi Yan <a class="moz-txt-link-rfc2396E"
href="mailto:ziy@nvidia.com" moz-do-not-send="true"><ziy@nvidia.com></a>
Reviewed-by: David Hildenbrand (Arm) <a class="moz-txt-link-rfc2396E"
href="mailto:david@kernel.org" moz-do-not-send="true"><david@kernel.org></a>
Tested-by: Venkat Rao Bagalkote <a class="moz-txt-link-rfc2396E"
href="mailto:venkat88@linux.ibm.com" moz-do-not-send="true"><venkat88@linux.ibm.com></a>
Signed-off-by: Sayali Patil <a class="moz-txt-link-rfc2396E"
href="mailto:sayalip@linux.ibm.com" moz-do-not-send="true"><sayalip@linux.ibm.com></a>
---
tools/testing/selftests/mm/charge_reserved_hugetlb.sh | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
index 447769657634..c9fe68b6fcf9 100755
--- a/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
+++ b/tools/testing/selftests/mm/charge_reserved_hugetlb.sh
@@ -65,7 +65,7 @@ function cleanup() {
if [[ -e $cgroup_path/hugetlb_cgroup_test2 ]]; then
rmdir $cgroup_path/hugetlb_cgroup_test2
fi
- echo 0 >/proc/sys/vm/nr_hugepages
+ echo "$nr_hugepgs" > /proc/sys/vm/nr_hugepages
echo CLEANUP DONE
}
</pre>
</blockquote>
</blockquote>
<font face="monospace">Previous reply was not formatted properly so
sending it again.<br>
<br>
AI review question
</font>
<blockquote type="cite"
cite="mid:2ba0f8d8a00fd049e8ed4b97e9ce8ee6b58a2892.1774591179.git.sayalip@linux.ibm.com">
<pre wrap="" class="moz-quote-pre">Does this cause excessive memory allocation churn during test execution?
Since cleanup() is invoked before and after every test iteration, restoring
the original nr_hugepages here (which could be thousands of pages) and then
immediately setting it back to 10 in the next test case forces the kernel
to repeatedly allocate and free many hugepages for every single test case.
Also, does this reliably restore nr_hugepages on test failures?
The test script runs with "set -e" active. If a test fails while the
background write_to_hugetlbfs process is still running, commands earlier
in cleanup() like "rmdir /mnt/huge" can fail with EBUSY because the
directory is still a mounted filesystem.
Due to "set -e", this failure causes the script to immediately exit,
completely bypassing this restore command at the end of cleanup().
Would it be better to restore the original value once at the very end.
</pre>
</blockquote>
<p data-start="0" data-end="153"><font face="monospace">Yes, it is
better to use an EXIT trap here to avoid unnecessary allocation<br>
churn and to ensure the original value is reliably restored on
all exit<br>
paths.</font></p>
<p data-start="155" data-end="474"><font face="monospace">A similar
change can also be applied to <code data-start="195"
data-end="224">hugetlb_reparenting_test.sh</code>. The<br>
test modifies <code data-start="244" data-end="258"
data-is-only-node="">nr_hugepages</code> during execution and
restores it from<br>
</font> <code data-start="297" data-end="308">cleanup()</code><font
face="monospace">, while also reconfiguring it again in <code
data-start="347" data-end="356">setup()</code>, which is<br>
invoked multiple times across the test flow. This can lead to
repeated<br>
allocation and freeing of hugepages.</font></p>
<p data-start="476" data-end="535"><font face="monospace">I will
prepare a patch for both tests and include it in v4.</font></p>
<p data-start="537" data-end="553" data-is-last-node=""
data-is-only-node=""><font face="monospace">Thanks,<br
data-start="544" data-end="547">
Sayali</font></p>
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