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Linux: transparent hugepage flag logic issue #37064

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jayaddison opened this issue Jan 25, 2021 · 0 comments
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Linux: transparent hugepage flag logic issue #37064

jayaddison opened this issue Jan 25, 2021 · 0 comments
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linux Issues and PRs related to the Linux platform.

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@jayaddison
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What steps will reproduce the bug?

Launching the node binary (when compiled with large pages support) with the --use-largepages flag enabled (either on or silent) may lead to this bug occurring.

What is the expected behavior?

Under Linux on a system where transparent hugepages are enabled (either in mode always or madvise), node launched with large pages enabled should make use of that system feature.

What do you see instead?

When --use-largepages=on (requesting non-silent operation), the following output is displayed when node is launched:

Large pages are not enabled.
Welcome to Node.js v16.0.0-pre.
Type ".help" for more information.
>

The state of transparent hugetable support can be examined on a running Linux system from a terminal by running the following command (with example output included):

$ cat /sys/kernel/mm/transparent_hugepage/enabled
always [madvise] never
@jayaddison jayaddison mentioned this issue Jan 25, 2021
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@targos targos added the linux Issues and PRs related to the Linux platform. label Jan 31, 2021
danielleadams pushed a commit that referenced this issue Feb 16, 2021
@jayaddison @danielleadams
src: read exactly two tokens from Linux THP sysfs config
9946c11 
There was an unexpected and hard-to-spot issue here:
the /sys/kernel/mm/transparent_hugepage/enabled file contains three
entries, and the std::ifstream reader was reading two values on each
loop iteration, resulting in incorrect behaviour.

Fixes: #37064

PR-URL: #37065
Reviewed-By: Darshan Sen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: James M Snell <[email protected]>
targos pushed a commit that referenced this issue May 1, 2021
@jayaddison @targos
src: read exactly two tokens from Linux THP sysfs config
00309ee 
There was an unexpected and hard-to-spot issue here:
the /sys/kernel/mm/transparent_hugepage/enabled file contains three
entries, and the std::ifstream reader was reading two values on each
loop iteration, resulting in incorrect behaviour.

Fixes: #37064

PR-URL: #37065
Reviewed-By: Darshan Sen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: James M Snell <[email protected]>
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Read exactly two tokens from Linux transparent huge pages sysfs config
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@targos @jayaddison