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From "Benoit Chesneau (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-2097) Avoid performance regression with a single fd
Date Sat, 05 Jul 2014 16:31:34 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-2097?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14052909#comment-14052909
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Benoit Chesneau commented on COUCHDB-2097:
------------------------------------------

Reads are not going via the updater process you're right I missed that change in bigcouch.


Though, except if I missed something, that doesn't change a lot. Now an update update the
latest db value by sending a message to the couch_server process which update the ets (shared
between all dbs). Then on read you open the db by sending a message to the couch_server and
then read the ets from it . The couch_server is now the new bottleneck. It could be improved
there by using a protected ets and accessing directly to it on open, but some tests recently
on similar design showed that relying on ets for that is slowing things compared to access
to one process.

I understand why you did that change. But  serialising read and writes is not a good idea
imo. Where we really only want serialibility. And we should fix the regression which is not
only about performance. 

I don't think we should simply closing the ticket and forget it. Maybe you're right we should
to supercede it by a new new ticket linking to this one. All these changes could happen in
master anyway, I don't think it is blocking the merge.







> Avoid performance regression with a single fd
> ---------------------------------------------
>
>                 Key: COUCHDB-2097
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-2097
>             Project: CouchDB
>          Issue Type: Improvement
>      Security Level: public(Regular issues) 
>          Components: BigCouch
>            Reporter: Paul Joseph Davis
>              Labels: release
>         Attachments: mike-wallace-fd-benchmarks.txt
>
>
> Part of one of our large enhancements required that we remove a CouchDB performance optimization
on having two file handles to each .couch file. We need to make sure that this doesn't negatively
impact performance.



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