Author: stefan2
Date: Tue Aug 26 14:27:47 2014
New Revision: 1620610
URL: http://svn.apache.org/r1620610
Log:
On the revprop-caching-ng branch: No functional change.
* BRANCH-README
(): Document that we are done and what we did.
Modified:
subversion/branches/revprop-caching-ng/BRANCH-README
Modified: subversion/branches/revprop-caching-ng/BRANCH-README
URL:
http://svn.apache.org/viewvc/subversion/branches/revprop-caching-ng/BRANCH-README?rev=1620610&r1=1620609&r2=1620610&view=diff
==============================================================================
--- subversion/branches/revprop-caching-ng/BRANCH-README (original)
+++ subversion/branches/revprop-caching-ng/BRANCH-README Tue Aug 26 14:27:47
2014
@@ -1,2 +1,28 @@
This branch is develop a revised revprop caching logic as discussed in
http://svn.haxx.se/dev/archive-2014-08/0273.shtml.
+
+Implementation is now complete. This is what got implemented:
+
+* Bind revprop caching feature to format bump. This prevents 1.8 processes
+ from using 1.9+ revprop generation files and vice versa. Also, 1.8
+ revprop generation files get automatically cleaned up during format
+ upgrade.
+
+* Always read the revprop generation from the respective file, keep the
+ latter open for quasi-SHM speed.
+* Non-caching processes will bump the generation number as well to keep
+ other, caching ones up-to-date.
+* Atomicy of revprop generation changes cannot be guaranteed (reader /
+ writer race condition). Use an MD5 checksum to ensure that consistent
+ has been read.
+* Open the generation file in read-only mode by default to prevent errors
+ on r/o file systems. This is an improvement over the 1.8 code.
+
+* Close and reopen the generation file when bumping its content for the
+ first time after we acquired the FS write lock. This keeps us from
+ reading from stale file buffers (lost updates) in case of networked
+ storage.
+* Always read the revprop data from disk when atomically changing it.
+ This is to prevent lost updates in the revprop data itself.
+
+* Removal of the whole named atomics code.
