From a284cb8472ec6bb027ebf3b936385601d8a8f414 Mon Sep 17 00:00:00 2001 From: Baolin Wang Date: Fri, 18 Oct 2024 11:00:28 +0800 Subject: [PATCH] mm: shmem: improve the tmpfs large folio read performance 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@linux.alibaba.com Signed-off-by: Baolin Wang Reviewed-by: Yang Shi Cc: David Hildenbrand Cc: Hugh Dickins Cc: Kefeng Wang Cc: Matthew Wilcox Signed-off-by: Andrew Morton --- mm/shmem.c | 34 ++++++++++++++++++++++++---------- 1 file changed, 24 insertions(+), 10 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 26aaddc52fd1..06da05f984da 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3094,13 +3094,13 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) 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; @@ -3121,6 +3121,10 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) error = -EIO; break; } + + if (folio_test_large(folio) && + folio_test_has_hwpoisoned(folio)) + fallback_page_copy = true; } /* @@ -3134,7 +3138,12 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) 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) { /* @@ -3142,10 +3151,15 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) * 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); @@ -3153,9 +3167,11 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) * 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 @@ -3173,8 +3189,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) } retval += ret; - offset += ret; - offset &= ~PAGE_MASK; iocb->ki_pos += ret; if (!iov_iter_count(to)) -- 2.25.1