From mboxrd@z Thu Jan 1 00:00:00 1970 From: ming.lei@canonical.com (Ming Lei) Date: Fri, 3 May 2013 17:12:45 +0800 Subject: [PATCH] ARM: DMA-mapping: mark all !DMA_TO_DEVICE pages in unmapping as clean Message-ID: <1367572365-18905-1-git-send-email-ming.lei@canonical.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org It is common for one sg to include many pages, so mark all these pages as clean to avoid unnecessary flushing on them in set_pte_at() or update_mmu_cache(). The patch might improve loading performance of applciation code a bit. On the below test code to read file(~1GByte size) from usb mass storage disk to buffer created with mmap(PROT_READ | PROT_EXEC) on Pandaboard, average ~1% improvement can be observed with the patch on 10 times test. #define _GNU_SOURCE #include #include #include #include #include #include #include #include unsigned int sum = 0; static unsigned long tv_diff(struct timeval *tv1, struct timeval *tv2) { return (tv2->tv_sec - tv1->tv_sec) * 1000000 + (tv2->tv_usec - tv1->tv_usec); } int main(int argc, char *argv[]) { char *mbuffer; int fd; int i; unsigned long page_size, size; struct stat stat; struct timeval t1, t2; page_size = getpagesize(); fd = open(argv[1], O_RDONLY); assert(fd >= 0); fstat(fd, &stat); size = stat.st_size; printf("%s: file %s, file size %lu, page size %lu\n", argv[0], read_filename, size, page_size); gettimeofday(&t1, NULL); mbuffer = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_SHARED, fd, 0); for (i = 0 ; i < size ; i += page_size) sum += mbuffer[i]; munmap(mbuffer, page_size); gettimeofday(&t2, NULL); printf("\tread mmaped time: %luus\n", tv_diff(&t1, &t2)); close(fd); } Cc: Nicolas Pitre Cc: Catalin Marinas Cc: Marek Szyprowski Cc: Russell King Signed-off-by: Ming Lei --- arch/arm/mm/dma-mapping.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index e9db6b4..e63124a 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -879,10 +879,23 @@ static void __dma_page_dev_to_cpu(struct page *page, unsigned long off, dma_cache_maint_page(page, off, size, dir, dmac_unmap_area); /* - * Mark the D-cache clean for this page to avoid extra flushing. + * Mark the D-cache clean for these pages to avoid extra flushing. */ - if (dir != DMA_TO_DEVICE && off == 0 && size >= PAGE_SIZE) - set_bit(PG_dcache_clean, &page->flags); + if (dir != DMA_TO_DEVICE && size >= PAGE_SIZE) { + unsigned long pfn; + size_t left = size; + + pfn = page_to_pfn(page); + if (off) { + pfn++; + left -= PAGE_SIZE - off % PAGE_SIZE; + } + while (left >= PAGE_SIZE) { + page = pfn_to_page(pfn++); + set_bit(PG_dcache_clean, &page->flags); + left -= PAGE_SIZE; + } + } } /** -- 1.7.9.5