From: Wang Shilong <wshilong@ddn.com>
Date: Tue, 25 Feb 2020 01:49:04 +0000 (+0800)
Subject: LU-13293 llite: don't abort readahead too aggressively
X-Git-Tag: 2.13.53~162
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=347ec7b87c766613d43aa340c3a1e6fa3cdcf044

LU-13293 llite: don't abort readahead too aggressively

We will stop readahead if we have covered @ria_end_idx_min
but lock contention case happen, this could cause a problem
with small read with SSF mode.

Because even lock contention happen, but every client could
potentially have a large consecutive pages to read, if this
is a 4K read, it will end up with a lot small read.

To fix this problem, at least allow readahead continue with
one stripe size, this is exact behavior before the commit

Without Patch:
Max Write: 13082.37 MiB/sec (13717.85 MB/sec)
Max Read:  854.17 MiB/sec (895.67 MB/sec)

With Patch:
Max Write: 12448.90 MiB/sec (13053.61 MB/sec)
Max Read: 23921.73 MiB/sec (25083.75 MB/sec)

Fixes: cfbeae9 ("LU-12043 llite: extend readahead locks for striped file")
Change-Id: I59963592f6dbe6babd746cd01441f4a99a8cafcb
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-on: https://review.whamcloud.com/37697
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
---

diff --git a/lustre/llite/rw.c b/lustre/llite/rw.c
index a11a038..89ea7fb 100644
--- a/lustre/llite/rw.c
+++ b/lustre/llite/rw.c
@@ -373,19 +373,30 @@ ll_read_ahead_pages(const struct lu_env *env, struct cl_io *io,
 			if (ra.cra_end_idx == 0 || ra.cra_end_idx < page_idx) {
 				pgoff_t end_idx;
 
+				/*
+				 * Do not shrink ria_end_idx at any case until
+				 * the minimum end of current read is covered.
+				 *
+				 * Do not extend read lock accross stripe if
+				 * lock contention detected.
+				 */
+				if (ra.cra_contention &&
+				    page_idx > ria->ria_end_idx_min) {
+					ria->ria_end_idx = *ra_end;
+					break;
+				}
+
 				cl_read_ahead_release(env, &ra);
 
 				rc = cl_io_read_ahead(env, io, page_idx, &ra);
 				if (rc < 0)
 					break;
 
-				/* Do not shrink ria_end_idx at any case until
-				 * the minimum end of current read is covered.
-				 * And only shrink ria_end_idx if the matched
-				 * LDLM lock doesn't cover more. */
-				if (page_idx > ra.cra_end_idx ||
-				    (ra.cra_contention &&
-				     page_idx > ria->ria_end_idx_min)) {
+				 /*
+				  * Only shrink ria_end_idx if the matched
+				  * LDLM lock doesn't cover more.
+				  */
+				if (page_idx > ra.cra_end_idx) {
 					ria->ria_end_idx = ra.cra_end_idx;
 					break;
 				}