[Tfug] Linux kernel tcp delay options 4e7uzube

[Bexley Hall]

Hi Adrian,

On 6/7/2013 2:27 PM, Adrian wrote:
> On Friday 07 June 2013 13:27, Nick Lopez wrote:
>
>>    Um, Dovecot supports multiple backends, but the default/suggested one is
>> the indexed Maildir. As long as you don't change the Maildir outside of
>> Dovecot (IMAP, deliver, etc) the indexes won't have to be rebuilt
>> constantly and can do their job. It copes just fine with Harry's email
>> hoarding. (29G, 1.7M messages) as well as my own more modest 1.4G/79K
>> Maildir.
>
> My local laptop mailstore is ~1.1G/150k.

Ouch!  Mailing lists?  (No point suggesting you move the messages
to some other medium/system since that means you'd need to come
up with an equivalent way of interfacing to *that* -- search, etc.)

> opening a folder on mdir with 20k+
> messages starts to slow down considerably, about 24sec on a 101k message
> folder just to read and process the index in Kmail.

Have you tried other clients to see if the delays are comparable?

> Trying to upload off my
> laptop mailstore to Cyrus, I'm only getting 15-20msg/sec transfer rate with
> minimal CPU and bandwidth usage on both sides, no I/O waits evident on the
> server, seems to be purely some sort of TCP delay (~3ms away from the
> server).

So, the times for connecting to Cyrus are orders of magnitude slower
than accesses on the mailstore local to your laptop (using the same
client?)  Or, are you comparing apples and orangutans, here?
("read and process the index" vs. "upload (message bodies) off my
laptop")

But, yes, something like !TCP_NODELAY may be playing a role.