From 5621b9f70e62da7b98d556de8cae39acd07f9e97 Mon Sep 17 00:00:00 2001
From: green <green>
Date: Mon, 3 Mar 2008 02:37:06 +0000
Subject: [PATCH] b=14748 r=adilger,jay
When traversing extent wating list queue for PR lock and meeting same or wider
lock without AST_SENT, we are guaranteed there is no other one like this down
the line, so we can return immediatelly
---
lustre/ChangeLog | 10 ++++++++++
lustre/ldlm/ldlm_extent.c | 28 ++++++++++++++++++++++++++++
2 files changed, 38 insertions(+)
diff --git a/lustre/ChangeLog b/lustre/ChangeLog
index fcac9f6acb..e9a30134da 100644
--- a/lustre/ChangeLog
+++ b/lustre/ChangeLog
@@ -761,6 +761,16 @@ Description: SNMP support enhancement
Details : Adding total number of sampled request for an MDS node in snmp
support.
+Severity : enhancement
+Bugzilla : 14748
+Description: Optimize ldlm waiting list processing for PR extent locks
+Details : When processing waiting list for read extent lock and meeting
+read
+ lock that is same or wider to it that is not contended, skip
+ processing rest of the list and immediatelly return current
+ status of conflictness, since we are guaranteed there are no
+ conflicting locks in the rest of the list.
+
--------------------------------------------------------------------------------
2007-08-10 Cluster File Systems, Inc. <info@clusterfs.com>
diff --git a/lustre/ldlm/ldlm_extent.c b/lustre/ldlm/ldlm_extent.c
index 3ff8e75f2a..1880c4352d 100644
--- a/lustre/ldlm/ldlm_extent.c
+++ b/lustre/ldlm/ldlm_extent.c
@@ -251,6 +251,34 @@ ldlm_extent_compat_queue(struct list_head *queue, struct ldlm_lock *req,
/* locks are compatible, overlap doesn't matter */
if (lockmode_compat(lock->l_req_mode, req_mode)) {
+ if (req_mode == LCK_PR &&
+ ((lock->l_policy_data.l_extent.start <=
+ req->l_policy_data.l_extent.start) &&
+ (lock->l_policy_data.l_extent.end >=
+ req->l_policy_data.l_extent.end))) {
+ /* If we met a PR lock just like us or wider,
+ and nobody down the list conflicted with
+ it, that means we can skip processing of
+ the rest of the list and safely place
+ ourselves at the end of the list, or grant
+ (dependent if we met an conflicting locks
+ before in the list).
+ In case of 1st enqueue only we continue
+ traversing if there is something conflicting
+ down the list because we need to make sure
+ that something is marked as AST_SENT as well,
+ in cse of empy worklist we would exit on
+ first conflict met. */
+ /* There IS a case where such flag is
+ not set for a lock, yet it blocks
+ something. Luckily for us this is
+ only during destroy, so lock is
+ exclusive. So here we are safe */
+ if (!(lock->l_flags & LDLM_FL_AST_SENT)) {
+ RETURN(compat);
+ }
+ }
+
/* non-group locks are compatible, overlap doesn't
matter */
if (likely(req_mode != LCK_GROUP))
--
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