[lustre-devel] [PATCH 14/25] lustre: clio: Skip prep for transients

[James Simmons <jsimmons@infradead.org>]

From: Patrick Farrell <farr0186@gmail.com>

The work done by cpo_prep() (etc) is unnecessary for
transient pages.  This gives only a minimal performance
boost and is better seen as a step towards removing the
cl_page abstraction for transient pages.

But, it does consistently give around 1% better
performance.

This patch reduces i/o time in ms/GiB by:
Write: 1 ms/GiB
Read: 1 ms/GiB

Totals:
Write: 169 ms/GiB
Read: 161 ms/GiB

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

With previous patches in series:
write        6028 MiB/s
read         6305 MiB/s

Plus this patch:
write        6071 MiB/s
read         6355 MiB/s

WC-bug-id: https://jira.whamcloud.com/browse/LU-13799
Lustre-commit: b8553978789ad3dd ("LU-13799 clio: Skip prep for transients")
Signed-off-by: Patrick Farrell <farr0186@gmail.com>
Reviewed-on: https://review.whamcloud.com/39448
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 fs/lustre/obdclass/cl_page.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/fs/lustre/obdclass/cl_page.c b/fs/lustre/obdclass/cl_page.c
index 41bd767..4bfa1c5 100644
--- a/fs/lustre/obdclass/cl_page.c
+++ b/fs/lustre/obdclass/cl_page.c
@@ -850,12 +850,15 @@ int cl_page_prep(const struct lu_env *env, struct cl_io *io,
 	if (crt >= CRT_NR)
 		return -EINVAL;
 
-	cl_page_slice_for_each(cl_page, slice, i) {
-		if (slice->cpl_ops->cpo_own)
-			result = (*slice->cpl_ops->io[crt].cpo_prep)(env, slice,
-								     io);
-		if (result != 0)
-			break;
+	if (cl_page->cp_type != CPT_TRANSIENT) {
+		cl_page_slice_for_each(cl_page, slice, i) {
+			if (slice->cpl_ops->cpo_own)
+				result = (*slice->cpl_ops->io[crt].cpo_prep)(env,
+									     slice,
+									     io);
+			if (result != 0)
+				break;
+		}
 	}
 
 	if (result >= 0) {
-- 
1.8.3.1

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