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 <zhucaifeng@unissoft-nj.com>
Signed-off-by: Yan, Zheng <zyan@redhat.com>
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 0c62868b..3c68e6a 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 @@
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_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 @@
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.
