I/O hammering (was: imp folder prefix)

[Egan]

On Tue, 29 May 2001 15:17:02 +0100, "Anil Madhavapeddy"
<anil@recoil.org> wrote:

>> if I turn on output buffering, PHP crashes consistently.
>
>Could you get a backtrace of this and report it as a PHP bug?   output
>buffering should be pretty stable in 4.0.5

If I get time.  But since I can run with no output buffering, I will
have to ignore that problem for now.

My immediate goal is to get IMP 2.3.7 in good enough shape to use.  It
doesn't have to be perfect, just good enough.

The only remaining obstacle is the big hit on disk I/O when building
the list of messages.  I thought UW-IMAP would be my I/O hog, but it's
not.  Just by listening to the disk in my test box, I can tell that
building the messages list is hammering the disk with I/O.

In comparison, when opening Outlook Express, which in turn opens an
instance on UW-IMAPd, I can hear one little hit to the disk, and then
nothing more for displaying the list of messages (stored in mbx
format).  With only that, I could probably live with non-persistent
IMAP connections, even using UW-IMAP.

But with IMP, OTOH, I can hear that first little I/O hit for opening
IMAPd, and immediately following that, I hear the disk being hammered
right before the list of messages appears.  IMP only does this with
the message list, it does not hit the disk hard with the folder list.

If the message list is very short, say only one message, I only hear a
very brief I/O hit to the disk.  But IMP must be doing enough I/O for
each message that multiplying that amount by 20 for a whole page adds
up to a big I/O hit.

Does anyone know why building the message list is so I/O intensive?
Can it be fixed?

Egan