[lustre-devel] [PATCH 12/25] lustre: lov: Improve DIO submit

[James Simmons]

From: Patrick Farrell <farr0186 at gmail.com>

Skip some unnecessary looping in page submission for the
DIO case.

This gives about a 2% improvement for AIO/DIO page
submission.

This patch reduces i/o time in ms/GiB by:
Write: 2 ms/GiB
Read: 2 ms/GiB

Totals:
Write: 172 ms/GiB
Read: 165 ms/GiB

mpirun -np 1  $IOR -w -r -t 64M -b 64G -o ./iorfile --posix.odirect

With previous patches in series:
write        7726 MiB/s
read         5899 MiB/s

Plus this patch:
write        5954 MiB/s
read         6217 MiB/s

WC-bug-id: https://jira.whamcloud.com/browse/LU-13799
Lustre-commit: d31647c017a390c9 ("LU-13799 lov: Improve DIO submit")
Signed-off-by: Patrick Farrell <farr0186 at gmail.com>
Reviewed-on: https://review.whamcloud.com/39446
Reviewed-by: Wang Shilong <wshilong at whamcloud.com>
Reviewed-by: Andreas Dilger <adilger at whamcloud.com>
Reviewed-by: Oleg Drokin <green at whamcloud.com>
Signed-off-by: James Simmons <jsimmons at infradead.org>
---
 fs/lustre/lov/lov_io.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/fs/lustre/lov/lov_io.c b/fs/lustre/lov/lov_io.c
index 9012ad6..2885943 100644
--- a/fs/lustre/lov/lov_io.c
+++ b/fs/lustre/lov/lov_io.c
@@ -1255,11 +1255,15 @@ static int lov_io_submit(const struct lu_env *env,
 	struct lov_io *lio = cl2lov_io(env, ios);
 	struct lov_io_sub *sub;
 	struct cl_page_list *plist = &lov_env_info(env)->lti_plist;
-	struct cl_page *page;
+	struct cl_page *page = cl_page_list_first(qin);
 	struct cl_page *tmp;
+	bool dio = false;
 	int index;
 	int rc = 0;
 
+	if (page->cp_type == CPT_TRANSIENT)
+		dio = true;
+
 	cl_page_list_init(plist);
 	while (qin->pl_nr > 0) {
 		struct cl_2queue *cl2q = &lov_env_info(env)->lti_cl2q;
@@ -1281,12 +1285,17 @@ static int lov_io_submit(const struct lu_env *env,
 		cl_page_list_move(&cl2q->c2_qin, qin, page);
 
 		index = page->cp_lov_index;
-		cl_page_list_for_each_safe(page, tmp, qin) {
-			/* this page is not on this stripe */
-			if (index != page->cp_lov_index)
-				continue;
-
-			cl_page_list_move(&cl2q->c2_qin, qin, page);
+		/* DIO is already split by stripe */
+		if (!dio) {
+			cl_page_list_for_each_safe(page, tmp, qin) {
+				/* this page is not on this stripe */
+				if (index != page->cp_lov_index)
+					continue;
+
+				cl_page_list_move(&cl2q->c2_qin, qin, page);
+			}
+		} else {
+			cl_page_list_splice(qin, &cl2q->c2_qin);
 		}
 
 		sub = lov_sub_get(env, lio, index);
-- 
1.8.3.1