[infinispan-issues] [JBoss JIRA] (ISPN-7324) DDAsyncInterceptor indirection slows down replicated reads

[Dan Berindei (JIRA)]

Dan Berindei created ISPN-7324:
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             Summary: DDAsyncInterceptor indirection slows down replicated reads
                 Key: ISPN-7324
                 URL: https://issues.jboss.org/browse/ISPN-7324
             Project: Infinispan
          Issue Type: Bug
          Components: Core
    Affects Versions: 9.0.0.Beta1
            Reporter: Dan Berindei
            Assignee: Dan Berindei
             Fix For: 9.0.0.Beta2


Local reads are fast enough, but the additional interceptors and stage callbacks in (transactional) replicated mode seem to impact with the async interceptor stack a lot more than the classic one.

One thing that's different with the new interceptors is that {{invokeNext()}} doesn't call {{command.acceptVisitor(nextInterceptor)}} directly. Instead it calls {{nextInterceptor.visitCommand()}}, and the interceptor decides whether to use double-dispatch (by extending {{DDAsyncInterceptor}}) or another strategy.

In theory this allows us to use simpler interceptors, e.g. having just the methods {{visitReadCommand()}}, {{visitWriteCommand()}}, and {{visitTxCommand()}}. {{CallInterceptor}} already calls {{command.perform()}} for each command. For now, however, most interceptors extend {{DDAsyncInterceptor}}, and tx replicated reads are slower than in 9.0.0.Alpha0.

With transactions, the {{VisitableCommand.acceptVisitor(}} call site in {{DDAsyncInterceptor.visitCommand}} is megamorphic (since the initial preload uses put, prepare, and commit). Adding a special check in {{invokeNext()}} to invoke {{command.acceptVisitor(nextInterceptor)}} didn't help, but adding a special check for  {{GetKeyValueCommand}} made a big difference on my machine:

|9.0.0.Alpha0 (CommandInterceptor)|4937351.255 ±(99.9%) 61665.164 ops/s|
|9.0.0.Beta1 (AsyncInterceptor)|4387466.151 ±(99.9%) 78665.887 ops/s|
|master before ISPN-6802 and ISPN-6803| 4247769.260 ±(99.9%) 133767.371 ops/s|
|master|   4710798.986 ±(99.9%) 166062.177 ops/s|
|master with GKVC special case| 5749357.895 ±(99.9%) 87338.878 ops/s|




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