From b5b98989dc7ed2093aeb76f2d0db79888582b0a2 Mon Sep 17 00:00:00 2001 From: "Zhu, Caifeng" Date: Thu, 8 Oct 2015 15:26:15 +0800 Subject: [PATCH] ceph: combine as many iovec as possile into one OSD request Both ceph_sync_direct_write and ceph_sync_read iterate iovec elements one by one, send one OSD request for each iovec. This is sub-optimal, We can combine serveral iovec into one page vector, and send an OSD request for the whole page vector. Signed-off-by: Zhu, Caifeng Signed-off-by: Yan, Zheng --- fs/ceph/file.c | 87 ++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 77 insertions(+), 10 deletions(-) diff --git a/fs/ceph/file.c b/fs/ceph/file.c index 0c62868b5c56..3c68e6aee2f0 100644 --- a/fs/ceph/file.c +++ b/fs/ceph/file.c @@ -34,6 +34,74 @@ * need to wait for MDS acknowledgement. */ +/* + * Calculate the length sum of direct io vectors that can + * be combined into one page vector. + */ +static size_t dio_get_pagev_size(const struct iov_iter *it) +{ + const struct iovec *iov = it->iov; + const struct iovec *iovend = iov + it->nr_segs; + size_t size; + + size = iov->iov_len - it->iov_offset; + /* + * An iov can be page vectored when both the current tail + * and the next base are page aligned. + */ + while (PAGE_ALIGNED((iov->iov_base + iov->iov_len)) && + (++iov < iovend && PAGE_ALIGNED((iov->iov_base)))) { + size += iov->iov_len; + } + dout("dio_get_pagevlen len = %zu\n", size); + return size; +} + +/* + * Allocate a page vector based on (@it, @nbytes). + * The return value is the tuple describing a page vector, + * that is (@pages, @page_align, @num_pages). + */ +static struct page ** +dio_get_pages_alloc(const struct iov_iter *it, size_t nbytes, + size_t *page_align, int *num_pages) +{ + struct iov_iter tmp_it = *it; + size_t align; + struct page **pages; + int ret = 0, idx, npages; + + align = (unsigned long)(it->iov->iov_base + it->iov_offset) & + (PAGE_SIZE - 1); + npages = calc_pages_for(align, nbytes); + pages = kmalloc(sizeof(*pages) * npages, GFP_KERNEL); + if (!pages) { + pages = vmalloc(sizeof(*pages) * npages); + if (!pages) + return ERR_PTR(-ENOMEM); + } + + for (idx = 0; idx < npages; ) { + size_t start; + ret = iov_iter_get_pages(&tmp_it, pages + idx, nbytes, + npages - idx, &start); + if (ret < 0) + goto fail; + + iov_iter_advance(&tmp_it, ret); + nbytes -= ret; + idx += (ret + start + PAGE_SIZE - 1) / PAGE_SIZE; + } + + BUG_ON(nbytes != 0); + *num_pages = npages; + *page_align = align; + dout("dio_get_pages_alloc: got %d pages align %zu\n", npages, align); + return pages; +fail: + ceph_put_page_vector(pages, idx, false); + return ERR_PTR(ret); +} /* * Prepare an open request. Preallocate ceph_cap to avoid an @@ -458,11 +526,10 @@ static ssize_t ceph_sync_read(struct kiocb *iocb, struct iov_iter *i, size_t start; ssize_t n; - n = iov_iter_get_pages_alloc(i, &pages, INT_MAX, &start); - if (n < 0) - return n; - - num_pages = (n + start + PAGE_SIZE - 1) / PAGE_SIZE; + n = dio_get_pagev_size(i); + pages = dio_get_pages_alloc(i, n, &start, &num_pages); + if (IS_ERR(pages)) + return PTR_ERR(pages); ret = striped_read(inode, off, n, pages, num_pages, checkeof, @@ -592,7 +659,7 @@ ceph_sync_direct_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos, CEPH_OSD_FLAG_WRITE; while (iov_iter_count(from) > 0) { - u64 len = iov_iter_single_seg_count(from); + u64 len = dio_get_pagev_size(from); size_t start; ssize_t n; @@ -611,14 +678,14 @@ ceph_sync_direct_write(struct kiocb *iocb, struct iov_iter *from, loff_t pos, osd_req_op_init(req, 1, CEPH_OSD_OP_STARTSYNC, 0); - n = iov_iter_get_pages_alloc(from, &pages, len, &start); - if (unlikely(n < 0)) { - ret = n; + n = len; + pages = dio_get_pages_alloc(from, len, &start, &num_pages); + if (IS_ERR(pages)) { ceph_osdc_put_request(req); + ret = PTR_ERR(pages); break; } - num_pages = (n + start + PAGE_SIZE - 1) / PAGE_SIZE; /* * throw out any page cache pages in this range. this * may block. -- 2.34.1