Jeremy Hylton wrote at 2004-3-1 14:01 -0500:
>It really would be good to get to the bottom of the bad ZEO performance
>for loading an object the first time. I won't have time to do it until
>after the ZODB 3.3 release, but I think it's a worthwhile effort to
>understand what ZEO is doing.
I instrumented "ClientStorage" to get precise timings
for ZEO operations. The obtained times are not bad:
When the data file was not yet in the operating system's
cache, loading an object took between 3 to 30 ms
with very high variance.
After the relevant parts of the data file have been cached
by the OS, time was between 1 to 3 ms per object, almost
independent from object size.
I obsevered loading of about 1.600 objects between several
hundred bytes and several kilobytes in size
mostly index data for a ZCatalog "FieldIndex".
I had disabled both the ZODB cache as well as
the ZEO client cache for my measurement.
ZEO client and server have been on the same machine (local
I interpreted these observations in the following way:
* time is dominated by the disc access
* time is largely independent of the object size (if
the object is in the OS disc cache)
* ZEO overhead is about 1 to 3 ms per object.
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