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https://issues.apache.org/jira/browse/PROTON-1408?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15944294#comment-15944294
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Alan Conway commented on PROTON-1408:
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How about we introduce an explicit `uintptr_t
pn_sequence_hashcode(pn_sequence_t n)` For now it can use the implementation
proposed above. It is very likely that a good hash function for sequence
numbers is NOT the same as a good hash function for void* pointers, so an
explicit hash function would give us a place to put a better algorithm if we
ever get to that.
I haven't found the culprit but different conversion sequences from int32_t
via void*/uintptr_t could give different results. The C integer conversion
rules for uintptr = int32 require sign extension, but casting int32 to void*
and *then* assigning to uintptr would give a bit copy - which is almost
certainly not the same if uintptr_t is 64 bits. So if we have slightly
different code paths it could give inconsistent results. An explicit hash
function that takes a pn_sequence_t will ensure there is only one way to do the
conversion and is self-explanatory.
> long-lived connections suffer large performance hit after many messages
> -----------------------------------------------------------------------
>
> Key: PROTON-1408
> URL: https://issues.apache.org/jira/browse/PROTON-1408
> Project: Qpid Proton
> Issue Type: Bug
> Components: proton-c
> Reporter: michael goulish
> Assignee: Alan Conway
> Attachments: jira_proton_1408_reproducer.tar.gz
>
>
> In long-running soak tests, in which connections are never taken down, I am
> seeing a sudden & severe performance degradation when the number of messages
> over the connection reaches about 6.4 billion.
> This is happening in tests with two senders, two receivers & one router
> intermediating.
> I have tried C libUV clients as well as CPP clients. Behavior is not
> identical, but I see sudden performance drop, ie. 8x throughput decrease or
> worse, in both cases.
> Alan / Ted / Ken see an issue in use of improper comparison logic in
> pn_do_disposition(), in transport.c . I am trying to prove this now.
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