I have a web app that continuously downloads listings of 18 directories residing on another server using CURLSMBS.
I was previously using CURLSMultiMBS.SharedInstance to load request curls, but I noticed that the listing times got longer and longer as the app ran, so I changed to a specific instance of CURLSMultiMBS so I could set its properties and changed the following from the defaults:
MaxHostConnections = 18
MaxTotalConnections = 18
MaxPipelineLength = 18
and wow 
the listing times plummeted by 10-20x!
I wish the various properties of CURLSMultiMBS were better-explained in the documentation. Their meanings are only cursorily explained, no defaults are listed, and the significance of the defaults isnāt explained. For example, here are the defaults from the debugger:
Does MaxHostConnections = 0 or MaxConnects = -1 mean no limit?
Does PenaltySize = 0 mean no penalties, or everything will be penalized?
maxconnects: if >0, a fixed limit of the maximum number of entries we are allowed to grow the connection cache to.
max_host_connections: if >0, a fixed limit of the maximum number of connections per host.
max_total_connections: if >0, a fixed limit of the maximum number of connections in total.
The penalty size properties are no longer used in CURL. I may deprecate them.
So I think the only change you made is to allow more connections.
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Thanks for the clarifications. So it seems the default MaxTotalConnections of 4 may be limiting the performance of CURLSMultiMBS.SharedInstance in some applications? Or am I wrong in assuming that the shared instanceās properties canāt be changed?
Yes. Please increase it and it may speed up if you have a lot of parallel transfers.
What values are good ones? Could higher values lead to problems?
Back in the day when I had really slow internet more connections led RapidWeaver choke and I had to use āSlowā or āAverageā as far as I remember:
