The patch titled Subject: mm: shmem: improve the tmpfs large folio read performance has been added to the -mm mm-unstable branch. Its filename is mm-shmem-improve-the-tmpfs-large-folio-read-performance.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shmem-improve-the-tmpfs-large-folio-read-performance.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: improve the tmpfs large folio read performance Date: Fri, 18 Oct 2024 11:00:28 +0800 tmpfs already supports PMD-sized large folios, but the tmpfs read operation still performs copying at PAGE_SIZE granularity, which is unreasonable. This patch changes tmpfs to copy data at folio granularity, which can improve the read performance, as well as changing to use folio related functions. Moreover, if a large folio has a subpage that is hwpoisoned, it will still fall back to page granularity copying. Use 'fio bs=64k' to read a 1G tmpfs file populated with 2M THPs, and I can see about 20% performance improvement, and no regression with bs=4k. Before the patch: READ: bw=10.0GiB/s After the patch: READ: bw=12.0GiB/s Link: https://lkml.kernel.org/r/2129a21a5b9f77d3bb7ddec152c009ce7c5653c4.1729218573.git.baolin.wang@xxxxxxxxxxxxxxxxx Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Reviewed-by: Yang Shi <shy828301@xxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/shmem.c | 34 ++++++++++++++++++++++++---------- 1 file changed, 24 insertions(+), 10 deletions(-) --- a/mm/shmem.c~mm-shmem-improve-the-tmpfs-large-folio-read-performance +++ a/mm/shmem.c @@ -3097,13 +3097,13 @@ static ssize_t shmem_file_read_iter(stru int error = 0; ssize_t retval = 0; - offset = iocb->ki_pos & ~PAGE_MASK; - for (;;) { struct folio *folio = NULL; struct page *page = NULL; unsigned long nr, ret; loff_t end_offset, i_size = i_size_read(inode); + bool fallback_page_copy = false; + size_t fsize; if (unlikely(iocb->ki_pos >= i_size)) break; @@ -3124,6 +3124,10 @@ static ssize_t shmem_file_read_iter(stru error = -EIO; break; } + + if (folio_test_large(folio) && + folio_test_has_hwpoisoned(folio)) + fallback_page_copy = true; } /* @@ -3137,7 +3141,12 @@ static ssize_t shmem_file_read_iter(stru break; } end_offset = min_t(loff_t, i_size, iocb->ki_pos + to->count); - nr = min_t(loff_t, end_offset - iocb->ki_pos, PAGE_SIZE - offset); + if (folio && likely(!fallback_page_copy)) + fsize = folio_size(folio); + else + fsize = PAGE_SIZE; + offset = iocb->ki_pos & (fsize - 1); + nr = min_t(loff_t, end_offset - iocb->ki_pos, fsize - offset); if (folio) { /* @@ -3145,10 +3154,15 @@ static ssize_t shmem_file_read_iter(stru * virtual addresses, take care about potential aliasing * before reading the page on the kernel side. */ - if (mapping_writably_mapped(mapping)) - flush_dcache_page(page); + if (mapping_writably_mapped(mapping)) { + if (likely(!fallback_page_copy)) + flush_dcache_folio(folio); + else + flush_dcache_page(page); + } + /* - * Mark the page accessed if we read the beginning. + * Mark the folio accessed if we read the beginning. */ if (!offset) folio_mark_accessed(folio); @@ -3156,9 +3170,11 @@ static ssize_t shmem_file_read_iter(stru * Ok, we have the page, and it's up-to-date, so * now we can copy it to user space... */ - ret = copy_page_to_iter(page, offset, nr, to); + if (likely(!fallback_page_copy)) + ret = copy_folio_to_iter(folio, offset, nr, to); + else + ret = copy_page_to_iter(page, offset, nr, to); folio_put(folio); - } else if (user_backed_iter(to)) { /* * Copy to user tends to be so well optimized, but @@ -3176,8 +3192,6 @@ static ssize_t shmem_file_read_iter(stru } retval += ret; - offset += ret; - offset &= ~PAGE_MASK; iocb->ki_pos += ret; if (!iov_iter_count(to)) _ Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are mm-shmem-fix-khugepaged-activation-policy-for-shmem.patch mm-shmem-update-iocb-ki_pos-directly-to-simplify-tmpfs-read-logic.patch mm-shmem-improve-the-tmpfs-large-folio-read-performance.patch