On 08/20/2014 02:47 PM, Michael McMahon wrote:
This still looks fine to me Peter.Thanks Michael
Hi Michael,Do I need another reviewer to push this to jdk9-dev ? I don't have a clear picture about how many reviewers are needed for what parts of JDK code.
Regards, Peter
On 19/08/14 11:51, Peter Levart wrote:Hi Michael,I have re-based the patch to the new jdk9 source layout. Nothing changes from the webrev.03 except paths:http://cr.openjdk.java.net/~plevart/jdk9-dev/InetAddress.Cache/webrev.04/Regards, Peter On 07/09/2014 01:52 PM, Peter Levart wrote:Hi Michael, Thanks for testing. I have prepared another webrev:http://cr.openjdk.java.net/~plevart/jdk9-dev/InetAddress.Cache/webrev.03/It only cleans up two comments suggested by Bernd (removed superfluous phrase "with 0" from statements about comparing time instants). So do you think this needs more testing / another review or can I consider this reviewed for jdk9-dev ?Regards, Peter On 07/07/2014 04:13 PM, Michael McMahon wrote:Peter,Thanks for the explanation. No. I think your change is good. I've run tests here locallyand I'm happy with it overall. Michael On 07/07/14 14:10, Peter Levart wrote:On 07/07/2014 12:59 PM, Michael McMahon wrote:Hi Peter,Is it necessary to remove the cache entry in the local host case (L1226) ? It seems redundant to cache it here, and also explicitly in the CachedLocalHost objectMichaelHi Michael, Thanks for looking into this.getLocalHost() seems to have a special hard-coded policy of positive caching for 5 seconds that is independent of general getByName() caching policy (30 seconds by default). The behaviour of original code that I'm trying to replicate is such that when getLocalHost() notices a change of local host name -> address mapping, the mapping in global cache for this change is also updated. I think this is to avoid situations like:Let's say the local host name is "cube": InetAddress addr1 = InetAddress.getLocalHost(); InetAddress addr2 = InetAddress.getByName("cube"); // addr1.equals(addr2) here// 5 seconds later, cube -> IP mapping is updated in DNS or /etc/hosts ...addr1 = InetAddress.getLocalHost(); addr2 = InetAddress.getByName("cube"); // if getLocalHost() did not update global cache,// addr1 (new IP address) would be different from addr2 (old IP address)Another way to accomplish similar guarantee would be to special-case the caching policy in global cache which would check whether the entry is for local host name and set 'expiryTime' accordingly. This would be a little different behaviourally, because InetAddress.getByName() would get a 5 second expiry for local host name too, regardless of whether InetAddress.getLocalHost() has been called at all. But we could get rid of special CachedLocalHost class then. Is such behavioural change warranted?Regards, PeterOn 02/07/14 12:56, Peter Levart wrote:Hi,I updated the webrev with first two suggestions from Bernd (expireTime instead of createTime and cacheNanos + only use putIfAbsent instead of get followed by putIfAbsent):http://cr.openjdk.java.net/~plevart/jdk9-dev/InetAddress.Cache/webrev.02/Thanks, Bernd.The id field in CachedAddresses is necessary for compareTo to never return 0 for two different instances (used as element in ConcurrentSkipListSet).For last two suggestions I'm not sure whether they are desired, so I'm currently leaving them as is.Regards, Peter On 07/01/2014 10:06 PM, Bernd Eckenfels wrote:Looks good, like it, Peter.some nits: instead of adding createTime and cacheNanos, only have aexpireAfter? L782: is it better to use putIfAbsent unconditionally, instead of get/putIfAbsent in NameServicdeAddr? L732: I am unsure about the id field, isnt it enough to have theidentity equality check for the replacement check and otherwise dependon equals()? L1223: What about moving the cache exiry inside the if (useCache)BTW1: might be the wrong RFR, but considering your good performance numbers for an active cache, would having 100ms or similiar default negative cache time make sense without impacting (visible) the semantic.Gruss Bernd Am Tue, 01 Jul 2014 20:35:57 +0200 schrieb Peter Levart <peter.lev...@gmail.com>:Hi, I propose a patch for this issue: https://bugs.openjdk.java.net/browse/JDK-7186258The motivation to re-design caching of InetAddress-es was not this issue though, but a desire to attack synchronization bottlenecks in methods like URL.equals and URL.hashCode which use host name to IPaddress mapping. I plan to tackle the synchronization in URL in afollow-up proposal, but I wanted to 1st iron-out the "leaves" of thecall-tree. Here's the proposed patch:http://cr.openjdk.java.net/~plevart/jdk9-dev/InetAddress.Cache/webrev.01/sun.net.InetAddressCachePolicy: - two static methods (get() and getNegative()) were synchronized. Removed synchronization and made underlying fields volatile. - also added a normalization of negative policy in setNegativeIfNotSet(). The logic in InetAddress doesn't cope withnegative values distinct from InetAddressCachePolicy.FOREVER (-1), sothis was a straight bug. The setIfNotSet() doesn't need this normalization, because checkValue() throws exception if passed-in value < InetAddressCachePolicy.FOREVER. java.net.InetAddress:- complete redesign of caching. Instead of distinct Positive/Negative caches, there's only one cache - a ConcurrentHashMap. The value inthe map knows if it contains positive or negative answer. - the design of this cache is similar but much simpler than java.lang.reflect.WeakCache, since it doesn't have to deal with WeakReferences and keys are simpler (just strings - hostnames).Similarity is in how concurrent requests for the same key (hostname) are synchronized when the entry is not cached yet, but still avoid synchronization when entry is cached. This preserves the behaviour oforiginal InetAddress caching code but simplifies it greatly (100+ lines removed). - I tried to preserve the interaction between InetAddress.getLocalHost() and InetAddress.getByName(). ThegetLocalHost() caches the local host address for 5 seconds privately. When it expires it performs new name service look-up and "refreshes" the entry in the InetAddress.getByName() cache although it has notexpired yet. I think this is meant to prevent surprises whengetLocalHost() returns newer address than getByName() which is calledafter that.- I also fixed the JDK-7186258 as a by-product (but don't know yethow to write a test for this issue - any ideas?) I created a JMH benchmark that tests the following methods: - InetAddress.getLocalHost() - InetAddress.getByName() (with positive and negative answer) Here're the results of running on my 4-core (8-threads) i7/Linux:http://cr.openjdk.java.net/~plevart/jdk9-dev/InetAddress.Cache/InetAddress.Cache_bench_results.01.pdfThe getByNameNegative() test does not show much improvement inpatched vs. original code. That's because by default the policy is toNOT cache negative answers. Requests for same hostname to the NameService(s) are synchronized. If"networkaddress.cache.negative.ttl" system property is set to some positive value, results are similar to those of getByNamePositive()test (the default policy for positive caching is 30 seconds). I ran the jtreg tests in test/java/net and have the same score aswith original unpatched code. I have 3 failing tests from originaland patched runs: JT Harness : Tests that failedjava/net/MulticastSocket/Promiscuous.java: Test for interference whentwo sockets are bound to the same port but joined to different multicast groups java/net/MulticastSocket/SetLoopbackMode.java: Test MulticastSocket.setLoopbackModejava/net/MulticastSocket/Test.java: IPv4 and IPv6 multicasting brokenon Linux And 1 test that had error trying to be run: JT Harness : Tests that had errors java/net/URLPermission/nstest/lookup.sh: Because of:test result: Error. Can't find source file: jdk/testlibrary/*.java indirectory-list:/home/peter/work/hg/jdk9-dev/jdk/test/java/net/URLPermission/nstest/home/peter/work/hg/jdk9-dev/jdk/test/lib/testlibrary All other 258 java/net tests pass. So what do you think? Regards, Peter
