[bookkeeper] branch branch-4.6 updated: Replaced synchronized with volatile read in BookieStatus

[sijie]

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sijie pushed a commit to branch branch-4.6
in repository https://gitbox.apache.org/repos/asf/bookkeeper.git


The following commit(s) were added to refs/heads/branch-4.6 by this push:
     new 052dc9d  Replaced synchronized with volatile read in BookieStatus
052dc9d is described below

commit 052dc9dc4dfa1eb4eeb06993f342078469192b18
Author: Matteo Merli <mme...@apache.org>
AuthorDate: Wed Mar 14 12:11:11 2018 -0700

    Replaced synchronized with volatile read in BookieStatus
    
    `BookieStatus.isInReadOnlyMode()` is being called from IO threads at each 
write request.
    
    Having `synchronized` method is a major source of contention between all 
these threads and caps the throughput and increases the latency.
    
    Replacing here with a `volatile` variable read. This will have the same 
exact behavior as today while removing the contention point.
    
    I think we could eventually even do a "dirty" read of that variable to 
further reduce the overhead of the volatile read.
    
    Author: Matteo Merli <mme...@apache.org>
    
    Reviewers: Ivan Kelly <iv...@apache.org>, Enrico Olivelli 
<eolive...@gmail.com>, Sijie Guo <si...@apache.org>
    
    This closes #1259 from merlimat/bookie-status-contention
    
    (cherry picked from commit e60085286f48c73ec779e45c84b4a76b2dc2da38)
    Signed-off-by: Sijie Guo <si...@apache.org>
---
 .../src/main/java/org/apache/bookkeeper/bookie/BookieStatus.java  | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/BookieStatus.java
 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/BookieStatus.java
index 560868a..59635c6 100644
--- 
a/bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/BookieStatus.java
+++ 
b/bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/BookieStatus.java
@@ -52,7 +52,7 @@ public class BookieStatus {
 
     private int layoutVersion;
     private long lastUpdateTime;
-    private BookieMode bookieMode;
+    private volatile BookieMode bookieMode;
 
 
     BookieStatus() {
@@ -61,11 +61,11 @@ public class BookieStatus {
         this.lastUpdateTime = INVALID_UPDATE_TIME;
     }
 
-    private synchronized BookieMode getBookieMode() {
+    private BookieMode getBookieMode() {
         return bookieMode;
     }
 
-    public synchronized boolean isInWritable() {
+    public boolean isInWritable() {
         return bookieMode.equals(BookieMode.READ_WRITE);
     }
 
@@ -78,7 +78,7 @@ public class BookieStatus {
         return false;
     }
 
-    synchronized boolean isInReadOnlyMode() {
+    boolean isInReadOnlyMode() {
         return bookieMode.equals(BookieMode.READ_ONLY);
     }
 

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