[dev] I/O hammering (was: imp folder prefix)

[Egan]

On Tue, 29 May 2001 17:09:32 +0100, "Anil Madhavapeddy"
<anil@recoil.org> wrote:

>Listening to your spindles isn't the most scientific way of solving the
>problem ;-)

Science was never my favorite subject.  I'm a CS grad who barely
squeaked through.  ;-)

I had also seen httpd take a big CPU hit, so I was thinking PHP,
instead of IMAPd, was causing the I/O.  But after what you said, I
pointed IMP to a different IMAP server which is remote, and you are
right, the big I/O hit stopped (at least on the machine running IMP).


>It would very useful if you could get an IMAP trace to
>figure out what extra commands IMP is sending that Outlook isn't.

I did a tcpdump of packets between the IMP box and the remote IMAPd
box to capture traffic associated with a screen of messages.  It looks
like an awful lot of talking just to get a list of 20 messages.

I don't know how to get an IMAP trace.  Any suggestions?


>Bear in mind that Outlook caches the message bodies to local disk, and
>IMP obviously cannot do this.  So Outlook just needs to compare message
>headers when the folder is reopened, whereas IMP needs to parse the
>whole lot.

Are you saying that IMP is getting message bodies just to display the
screen which shows a list of 20 messages?


Egan