On 06/05/2024 09:46, Baolin Wang wrote: > Anonymous pages have already been supported for multi-size (mTHP) allocation > through commit 19eaf44954df, that can allow THP to be configured through the > sysfs interface located at '/sys/kernel/mm/transparent_hugepage/hugepage-XXkb/enabled'. > > However, the anonymous shared pages will ignore the anonymous mTHP rule > configured through the sysfs interface, and can only use the PMD-mapped > THP, that is not reasonable. Many implement anonymous page sharing through > mmap(MAP_SHARED | MAP_ANONYMOUS), especially in database usage scenarios, > therefore, users expect to apply an unified mTHP strategy for anonymous pages, > also including the anonymous shared pages, in order to enjoy the benefits of > mTHP. For example, lower latency than PMD-mapped THP, smaller memory bloat > than PMD-mapped THP, contiguous PTEs on ARM architecture to reduce TLB miss etc. > > The primary strategy is similar to supporting anonymous mTHP. Introduce > a new interface '/mm/transparent_hugepage/hugepage-XXkb/shmem_enabled', > which can have all the same values as the top-level Didn't we agree that "force" would not be supported for now, and would return an error when attempting to set for a non-PMD-size hugepage-XXkb/shmem_enabled (or indirectly through inheritance)? > '/sys/kernel/mm/transparent_hugepage/shmem_enabled', with adding a new > additional "inherit" option. By default all sizes will be set to "never" > except PMD size, which is set to "inherit". This ensures backward compatibility > with the shmem enabled of the top level, meanwhile also allows independent > control of shmem enabled for each mTHP. > > Use the page fault latency tool to measure the performance of 1G anonymous shmem > with 32 threads on my machine environment with: ARM64 Architecture, 32 cores, > 125G memory: > base: mm-unstable > user-time sys_time faults_per_sec_per_cpu faults_per_sec > 0.04s 3.10s 83516.416 2669684.890 > > mm-unstable + patchset, anon shmem mTHP disabled > user-time sys_time faults_per_sec_per_cpu faults_per_sec > 0.02s 3.14s 82936.359 2630746.027 > > mm-unstable + patchset, anon shmem 64K mTHP enabled > user-time sys_time faults_per_sec_per_cpu faults_per_sec > 0.08s 0.31s 678630.231 17082522.495 > > From the data above, it is observed that the patchset has a minimal impact when > mTHP is not enabled (some fluctuations observed during testing). When enabling 64K > mTHP, there is a significant improvement of the page fault latency. > > TODO: > - Support mTHP for tmpfs. > - Do not split the large folio when share memory swap out. > - Can swap in a large folio for share memory. > > Changes from RFC: > - Rebase the patch set against the new mm-unstable branch, per Lance. > - Add a new patch to export highest_order() and next_order(). > - Add a new patch to align mTHP size in shmem_get_unmapped_area(). > - Handle the uffd case and the VMA limits case when building mapping for > large folio in the finish_fault() function, per Ryan. > - Remove unnecessary 'order' variable in patch 3, per Kefeng. > - Keep the anon shmem counters' name consistency. > - Modify the strategy to support mTHP for anonymous shmem, discussed with > Ryan and David. > - Add reviewed tag from Barry. > - Update the commit message. > > Baolin Wang (8): > mm: move highest_order() and next_order() out of the THP config > mm: memory: extend finish_fault() to support large folio > mm: shmem: add an 'order' parameter for shmem_alloc_hugefolio() > mm: shmem: add THP validation for PMD-mapped THP related statistics > mm: shmem: add multi-size THP sysfs interface for anonymous shmem > mm: shmem: add mTHP support for anonymous shmem > mm: shmem: add mTHP size alignment in shmem_get_unmapped_area > mm: shmem: add mTHP counters for anonymous shmem > > Documentation/admin-guide/mm/transhuge.rst | 29 ++ > include/linux/huge_mm.h | 35 ++- > mm/huge_memory.c | 17 +- > mm/memory.c | 43 ++- > mm/shmem.c | 335 ++++++++++++++++++--- > 5 files changed, 387 insertions(+), 72 deletions(-) >
