Hi I've been doing some performance work lately in Seaside. Long story short Seaside (and I guess AIDA too) spends of if it's rendering time in WriteStream (#nextPutAll:, #nextPut:).
The way WriteStream >> #pastEndPut: behaves is not really ideal for Seaside. It grows the underlying collection by just enough to accommodate the argument collection (or 20 which ever is bigger). Now image the following not very unlikely scenario. You start with a 4k buffer and put on average a 10 element collection (remember all those tags are put individually) until you have a 16k response. You allocate more than a thousand intermediary collections to get there. What would be better suited for Seaside is doubling the required size. In the worst case that would mean wasting 50% of memory but it would make the overhead of creating intermediary collections logarithmic. In the given example that would take us only three allocations to get there. Now I do realize there are other applications for Pharo where this strategy is not ideal and this is not a killer for us. I just wanted to shed some light and this and ask whether other projects are in a similar situation. To get a feel how allocation limited Seaside is: avoiding one allocation of a 16k ByteArray per request can make a difference in throughput between 10 Mbyte/s and 30 Mbyte/s (see "[Progress Report] Zinc HTTP Components"). If anybody knows a way to make allocation of large young space objects faster (Set GC Bias to Grow?, #vmParameterAt:put:?) I'd like to hear it. Cheers Philippe
