[Dovecot] performance problems with IMAPS

[Linda Walsh]

I've noticed this before and wasn't sure of the problem -- sending large 
files from FF.

I tracked it down, and the problem is in dovecot when it is saving the 
mail to my 'Record' (Outbox)...

It's saving the file in tiny chunks....

Looking at a few, I see:
4148 bytes
2116 bytes
1604 bytes
692 bytes

The latency is killing it.  I see the TCP window size being as high as 
17069 with 7678 being common.
The sendmail latency isn't spectacular, but at least uses ~64K packets.  
So wazzup with dovecot?

I don't recall this being so much an issue with the old uwash imaps, but 
then it's been a while since I've
used it and maybe my files weren't as large.

But it can take several minutes to save a file to a record file that 
takes <1 second over network CIFS.

Anyway to up the size of minimum packet size to 128K or more? 

Ideal packet size on my network is about 16MB under CIFS...with benefits 
seen even using 256MB packet sizes....

Is there a place to tune this that I don't know about?


Thanks....