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We have also noticed that - the same plugin code renders slower in Confluence 6 than in Confluence 5. In fact. our macros rendering is not that slower (How to enable logging for ConfiForms add-on), however, the output to user is sent considerbly slower than in Confluence 5.
We think, that this might be one of the reasons https://confluence.atlassian.com/confkb/slow-page-rendering-of-large-pages-due-to-http-post-limitations-183137.html
We have also noticed tht that rendering times (in fact the time used to sent the rendered output to user) has been improved in Confluence 6.8.x, but is still is slower than on Confluence 5. We are continuing to investigate this issue and looking for solutions.
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