On Thu, Dec 17, 2020 at 12:28 PM Guenter Roeck firstname.lastname@example.org wrote:
On Wed, Oct 14, 2020 at 12:53:08AM +0000, Kalesh Singh wrote:
Android needs to move large memory regions for garbage collection. The GC requires moving physical pages of multi-gigabyte heap using mremap. During this move, the application threads have to be paused for correctness. It is critical to keep this pause as short as possible to avoid jitters during user interaction.
Optimize mremap for >= 1GB-sized regions by moving at the PUD/PGD level if the source and destination addresses are PUD-aligned. For CONFIG_PGTABLE_LEVELS == 3, moving at the PUD level in effect moves PGD entries, since the PUD entry is “folded back” onto the PGD entry. Add HAVE_MOVE_PUD so that architectures where moving at the PUD level isn't supported/tested can turn this off by not selecting the config.
Fix build test error from v1 of this series reported by kernel test robot in .
Signed-off-by: Kalesh Singh email@example.com Reported-by: kernel test robot firstname.lastname@example.org Acked-by: Kirill A. Shutemov email@example.com Cc: Andrew Morton firstname.lastname@example.org
I thought I reported it, but maybe I didn't. This patch causes all 'parisc' qemu emulations to fail. Typical log:
Freeing unused kernel memory: 604K Write protected read-only-after-init data: 2k rodata_test: end of .rodata is not page size aligned Run /sbin/init as init process process '/bin/busybox' started with executable stack Failed to execute /sbin/init (error -12)
Reverting this patch fixes the problem.
Bisect log from linux-next below. The patch (and thus the problem) are now in mainline Linux.
Thanks for reporting. We enabled this on x86 and arm64. Investigating what the root cause is now.
# bad: [7bba37a1591369e2e506d599b8f5d7d0516b2dbc] Add linux-next specific files for 20201214 # good: [0477e92881850d44910a7e94fc2c46f96faa131f] Linux 5.10-rc7 git bisect start 'HEAD' 'v5.10-rc7' # good: [fe5c40ab90a1f82ba97294637eaf875cfdd7a05f] Merge remote-tracking branch 'nand/nand/next' git bisect good fe5c40ab90a1f82ba97294637eaf875cfdd7a05f # good: [674a0d6de8bd290671f7dff405205871a70300b3] Merge remote-tracking branch 'spi/for-next' git bisect good 674a0d6de8bd290671f7dff405205871a70300b3 # good: [8623dae312f73a2ea3230b1c648d3004cfc224ce] Merge remote-tracking branch 'vfio/next' git bisect good 8623dae312f73a2ea3230b1c648d3004cfc224ce # good: [dd26635f54bcd8e5d4e875a209f82a0423ba9c08] Merge remote-tracking branch 'gpio/for-next' git bisect good dd26635f54bcd8e5d4e875a209f82a0423ba9c08 # good: [86e9c9a734889fe437442e0a35eb4c61d319cb47] Merge remote-tracking branch 'memblock/for-next' git bisect good 86e9c9a734889fe437442e0a35eb4c61d319cb47 # bad: [3452331fda80b1cb5e121e6718ca6c07264382b2] userfaultfd: add user-mode only option to unprivileged_userfaultfd sysctl knob git bisect bad 3452331fda80b1cb5e121e6718ca6c07264382b2 # bad: [19f468d54fcffc3f98b71e3e12ff23726767d953] mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio git bisect bad 19f468d54fcffc3f98b71e3e12ff23726767d953 # good: [d89f3ababcac54493a4cb0582c61eb5f426b44e3] mm: remove pagevec_lookup_range_nr_tag() git bisect good d89f3ababcac54493a4cb0582c61eb5f426b44e3 # good: [eba8373dcb40d30952f31d5fc0cff56b78f46273] mm/mlock: remove __munlock_isolate_lru_page() git bisect good eba8373dcb40d30952f31d5fc0cff56b78f46273 # good: [8831d3f3564beba0f3f1b5291c88b35725bc45c9] xen/unpopulated-alloc: consolidate pgmap manipulation git bisect good 8831d3f3564beba0f3f1b5291c88b35725bc45c9 # bad: [b8d53d70851821d8a2040ddca3aa6ee88fc8aaec] mm/page_vma_mapped.c: add colon to fix kernel-doc markups error for check_pte git bisect bad b8d53d70851821d8a2040ddca3aa6ee88fc8aaec # bad: [e77846c3da1862faa25c08e186a62b03e98c862f] x86: mremap speedup - Enable HAVE_MOVE_PUD git bisect bad e77846c3da1862faa25c08e186a62b03e98c862f # bad: [72ad8951bac1c559ea1b691a0b035fb339e4d71d] mm: speedup mremap on 1GB or larger regions git bisect bad 72ad8951bac1c559ea1b691a0b035fb339e4d71d # good: [fa94bfe31609787501a1ff8d7659ade5734ec4e5] kselftests: vm: add mremap tests git bisect good fa94bfe31609787501a1ff8d7659ade5734ec4e5 # first bad commit: [72ad8951bac1c559ea1b691a0b035fb339e4d71d] mm: speedup mremap on 1GB or larger regions
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