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From Thomas Mueller <muel...@adobe.com>
Subject Re: [jr3] Tree model
Date Wed, 29 Feb 2012 09:03:06 GMT
Hi,

>I don't have a real test case. But assume this:
>
>  * 50 people updating content (in different areas of the tree)
>  * another 100 people reading from the repository
>  * digital asset import with workflow processing (involving repository
>    updates, too).

OK, I see what you mean with "concurrent". On a high level, all operations
are "concurrent". On a low level however, those operations are split into
read requests and more or less small commits. In that case, what matters
most is read and write throughput. If throughput is low, performance is
bad for everybody, no matter to what level the writes are "concurrent"
internally. If write throughput is high, performance for everybody is
good. Anyway at some point you do have to serialize uncached reads and
writes, because the disk doesn't support concurrent reads and writes.

If possible, reads should be cached, and writes should be buffered.
Buffering writes would help a lot more than trying to write concurrently
to the lowest possible level (just above the disk). Unfortunately, the
current MicroKernel API doesn't really support buffering writes, because
the commit method returns the new revision. Possibly we should add a
"asynchronous commit" method that doesn't return the revision, similar to
asynchronous writes in UnSQL:
http://unql.sqlite.org/index.html/doc/tip/doc/syntax/all.wiki or low
priority inserts / updates in MySQL:
http://dev.mysql.com/doc/refman/5.0/en/update.html

But having a good automated test case would help.


Regards,
Thomas


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