The patch titled Subject: mm: shmem: add a kernel command line to change the default huge policy for tmpfs has been added to the -mm mm-unstable branch. Its filename is mm-shmem-add-a-kernel-command-line-to-change-the-default-huge-policy-for-tmpfs.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-add-a-kernel-command-line-to-change-the-default-huge-policy-for-tmpfs.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Subject: mm: shmem: add a kernel command line to change the default huge policy for tmpfs Date: Thu, 28 Nov 2024 15:40:42 +0800 Now the tmpfs can allow to allocate any sized large folios, and the default huge policy is still preferred to be 'never'. Due to tmpfs not behaving like other file systems in some cases as previously explained by David[1]: : I think I raised this in the past, but tmpfs/shmem is just like any : other file system .. except it sometimes really isn't and behaves much : more like (swappable) anonymous memory. (or mlocked files) : : There are many systems out there that run without swap enabled, or with : extremely minimal swap (IIRC until recently kubernetes was completely : incompatible with swapping). Swap can even be disabled today for shmem : using a mount option. : : That's a big difference to all other file systems where you are : guaranteed to have backend storage where you can simply evict under : memory pressure (might temporarily fail, of course). : : I *think* that's the reason why we have the "huge=" parameter that also : controls the THP allocations during page faults (IOW possible memory : over-allocation). Maybe also because it was a new feature, and we only : had a single THP size. Thus adding a new command line to change the default huge policy will be helpful to use the large folios for tmpfs, which is similar to the 'transparent_hugepage_shmem' cmdline for shmem. [1] https://lore.kernel.org/all/cbadd5fe-69d5-4c21-8eb8-3344ed36c721@xxxxxxxxxx/ Link: https://lkml.kernel.org/r/ff390b2656f0d39649547f8f2cbb30fcb7e7be2d.1732779148.git.baolin.wang@xxxxxxxxxxxxxxxxx Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Cc: Barry Song <baohua@xxxxxxxxxx> Cc: Daniel Gomez <da.gomez@xxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Cc: Lance Yang <ioworker0@xxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Ryan Roberts <ryan.roberts@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/admin-guide/kernel-parameters.txt | 7 ++++ Documentation/admin-guide/mm/transhuge.rst | 6 +++ mm/shmem.c | 23 +++++++++++++- 3 files changed, 35 insertions(+), 1 deletion(-) --- a/Documentation/admin-guide/kernel-parameters.txt~mm-shmem-add-a-kernel-command-line-to-change-the-default-huge-policy-for-tmpfs +++ a/Documentation/admin-guide/kernel-parameters.txt @@ -6987,6 +6987,13 @@ See Documentation/admin-guide/mm/transhuge.rst for more details. + transparent_hugepage_tmpfs= [KNL] + Format: [always|within_size|advise|never] + Can be used to control the default hugepage allocation policy + for the tmpfs mount. + See Documentation/admin-guide/mm/transhuge.rst + for more details. + trusted.source= [KEYS] Format: <string> This parameter identifies the trust source as a backend --- a/Documentation/admin-guide/mm/transhuge.rst~mm-shmem-add-a-kernel-command-line-to-change-the-default-huge-policy-for-tmpfs +++ a/Documentation/admin-guide/mm/transhuge.rst @@ -332,6 +332,12 @@ allocation policy for the internal shmem seven valid policies for shmem (``always``, ``within_size``, ``advise``, ``never``, ``deny``, and ``force``). +Similarly to ``transparent_hugepage_shmem``, you can control the default +hugepage allocation policy for the tmpfs mount by using the kernel parameter +``transparent_hugepage_tmpfs=<policy>``, where ``<policy>`` is one of the +four valid policies for tmpfs (``always``, ``within_size``, ``advise``, +``never``). The tmpfs mount default policy is ``never``. + In the same manner as ``thp_anon`` controls each supported anonymous THP size, ``thp_shmem`` controls each supported shmem THP size. ``thp_shmem`` has the same format as ``thp_anon``, but also supports the policy --- a/mm/shmem.c~mm-shmem-add-a-kernel-command-line-to-change-the-default-huge-policy-for-tmpfs +++ a/mm/shmem.c @@ -553,6 +553,7 @@ static bool shmem_confirm_swap(struct ad /* ifdef here to avoid bloating shmem.o when not necessary */ static int shmem_huge __read_mostly = SHMEM_HUGE_NEVER; +static int tmpfs_huge __read_mostly = SHMEM_HUGE_NEVER; /** * shmem_mapping_size_orders - Get allowable folio orders for the given file size. @@ -4951,7 +4952,12 @@ static int shmem_fill_super(struct super sbinfo->gid = ctx->gid; sbinfo->full_inums = ctx->full_inums; sbinfo->mode = ctx->mode; - sbinfo->huge = ctx->huge; +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + if (ctx->seen & SHMEM_SEEN_HUGE) + sbinfo->huge = ctx->huge; + else + sbinfo->huge = tmpfs_huge; +#endif sbinfo->mpol = ctx->mpol; ctx->mpol = NULL; @@ -5502,6 +5508,21 @@ static int __init setup_transparent_huge } __setup("transparent_hugepage_shmem=", setup_transparent_hugepage_shmem); +static int __init setup_transparent_hugepage_tmpfs(char *str) +{ + int huge; + + huge = shmem_parse_huge(str); + if (huge < 0) { + pr_warn("transparent_hugepage_tmpfs= cannot parse, ignored\n"); + return huge; + } + + tmpfs_huge = huge; + return 1; +} +__setup("transparent_hugepage_tmpfs=", setup_transparent_hugepage_tmpfs); + static char str_dup[PAGE_SIZE] __initdata; static int __init setup_thp_shmem(char *str) { _ Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are mm-factor-out-the-order-calculation-into-a-new-helper.patch mm-shmem-change-shmem_huge_global_enabled-to-return-huge-order-bitmap.patch mm-shmem-add-large-folio-support-for-tmpfs.patch mm-shmem-add-a-kernel-command-line-to-change-the-default-huge-policy-for-tmpfs.patch docs-tmpfs-drop-fadvise-from-the-documentation.patch