improving concurrency/performance

[Jure Pečar]

On Mon, 7 Nov 2005 12:41:03 -0500 (EST)
"John Madden" <jmadden at ivytech.edu> wrote:

> Perhaps it's worth repeating: With a single imapcopy process, the whole thing goes
> along pretty quickly, but drops off significantly with a second process and comes
> to basically a crawl with just 5 processes running concurrently.  I gambled that I
> could shorten my migration by running more than one at a time since one only seems
> to raise the load on the box to 0.80.  With 5, I'm only able to get it to around
> 2.5 and only briefly as the throughput starts to drop off.

That is a start. Try to strace -tt all of imapd processes running
concurrently and examine in which syscalls most time is spent. I hope that
would give you at least a lead ... 

For example, on my production system I see some suspicious long pauses at
fcntl64(0x8, 0x7, 0xsomeaddr, 0xsomeotheraddr) calls ... lets dig what this
is.


-- 

Jure Pečar
http://jure.pecar.org/