Public bug reported: in sysfs.conf: kernel/mm/transparent_hugepage/defrag = defer
After systemctl restart sysfsutils.service: cat kernel/mm/transparent_hugepage/defrag result: always defer [defer+madvise] madvise never Problem seems to be related to lines 49-50 of /etc/init.d/sysfsutils, the use of echo -n followed by echo. If you reverse them to do echo followed by echo -n then it applies correctly. Example of "echo -n defer > defrag": Mythmaster mattaw ⋯ kernel mm transparent_hugepage sudo dash -c "echo -n defer > defrag" Mythmaster mattaw ⋯ kernel mm transparent_hugepage cat * always defer [defer+madvise] madvise never - incorrect Example of "echo defer > defrag": Mythmaster mattaw ⋯ kernel mm transparent_hugepage sudo dash -c "echo defer > defrag" Mythmaster mattaw ⋯ kernel mm transparent_hugepage cat * always [defer] defer+madvise madvise never - correct Note: this is a bug in the kernel handling of the defrag interface: https://github.com/torvalds/linux/blob/v4.13/mm/huge_memory.c: Lines 237-255 or so. Test is memcmp between the input buffer and "defer+madvise", with a newline memcmp doesn't match. Without it matches: } else if (!memcmp("defer+madvise", buf, min(sizeof("defer+madvise")-1, count))) { will match either defer or defer+madvise. Unfortunate. ** Affects: sysfsutils (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to sysfsutils in Ubuntu. https://bugs.launchpad.net/bugs/1745780 Title: Setting from sysfs.conf incorrectly applied Status in sysfsutils package in Ubuntu: New Bug description: in sysfs.conf: kernel/mm/transparent_hugepage/defrag = defer After systemctl restart sysfsutils.service: cat kernel/mm/transparent_hugepage/defrag result: always defer [defer+madvise] madvise never Problem seems to be related to lines 49-50 of /etc/init.d/sysfsutils, the use of echo -n followed by echo. If you reverse them to do echo followed by echo -n then it applies correctly. Example of "echo -n defer > defrag": Mythmaster mattaw ⋯ kernel mm transparent_hugepage sudo dash -c "echo -n defer > defrag" Mythmaster mattaw ⋯ kernel mm transparent_hugepage cat * always defer [defer+madvise] madvise never - incorrect Example of "echo defer > defrag": Mythmaster mattaw ⋯ kernel mm transparent_hugepage sudo dash -c "echo defer > defrag" Mythmaster mattaw ⋯ kernel mm transparent_hugepage cat * always [defer] defer+madvise madvise never - correct Note: this is a bug in the kernel handling of the defrag interface: https://github.com/torvalds/linux/blob/v4.13/mm/huge_memory.c: Lines 237-255 or so. Test is memcmp between the input buffer and "defer+madvise", with a newline memcmp doesn't match. Without it matches: } else if (!memcmp("defer+madvise", buf, min(sizeof("defer+madvise")-1, count))) { will match either defer or defer+madvise. Unfortunate. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/sysfsutils/+bug/1745780/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
