[Dovecot] nfs and pop3

[Timo Sirainen]

On Wed, 2006-01-25 at 22:55 +0100, Marten Lehmann wrote:
> Hi,
> 
> I'm working with dovecot 1.0.beta2 for pop3 only and have set 
> index=memory, so no indizes are created on the disk. pop3_uidl_format is 
> set to %f. The maildirs are located on an nfs-share.
> So generally, this setup is very similar to what qmail-popup and 
> qmail-pop3d does. However, everytime I'm switching from qmail-pop3d to 
> dovecot, the system load increases from less than 2 to more than 30 (and 
> later up to 60 and more). The problem is I/O, probably caused by 
> nfs-access. But what is causing this accesses? qmail-pop3d just takes 
> filenames as UIDL, and moves the mails from new to cur, reads them to 
> send them to the client or deletes them. This is working fine.
> But what is dovecot doing? There must be a lot more things that cause 
> that high I/O load. Indizes are disabled, so they cannot be the cause 
> any longer.
> Any ideas? I just want to switch to dovecot at some point finally 
> without having qmail-pop3d as backup.

The difference is that with Dovecot LIST command is returning the
messages' exact size with CR+LF linefeeds. I didn't actually know that
this wasn't required with POP3.

Now, the simplest fix in your case would be to just make Dovecot return
the message's physical size with stat(). But I'm not sure if this is a
good default behavior. The physical size isn't used by IMAP, so if the
mailbox has both POP3 and IMAP access, it needs to store both physical
and virtual sizes to cache file..

Anyway, this patch should help you:

Index: src/pop3/client.c
===================================================================
RCS file: /var/lib/cvs/dovecot/src/pop3/client.c,v
retrieving revision 1.60
diff -u -r1.60 client.c
--- src/pop3/client.c	14 Jan 2006 18:48:17 -0000	1.60
+++ src/pop3/client.c	26 Jan 2006 19:54:41 -0000
@@ -85,9 +85,9 @@
 		buffer_set_used_size(message_sizes_buf, 0);
 
 		failed = FALSE;
-		mail = mail_alloc(t, MAIL_FETCH_VIRTUAL_SIZE, NULL);
+		mail = mail_alloc(t, MAIL_FETCH_PHYSICAL_SIZE, NULL);
 		while (mailbox_search_next(ctx, mail) > 0) {
-			uoff_t size = mail_get_virtual_size(mail);
+			uoff_t size = mail_get_physical_size(mail);
 
 			if (size == (uoff_t)-1) {
 				failed = TRUE;

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