Re: Comparing mail backends

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

Kai.Grossjohann@CS.Uni-Dortmund.DE (Kai Großjohann) writes:

> Each kind of mail backend has its own advantages and disadvantages.
> Here, I'd like to learn something about speed.
> 
> Which operations are particularly slow and which operations are
> particularly fast for the following backends?
> 
>   - nnmbox
>   - nnbabyl
>   - nnfolder
>   - nnmh
>   - nnml
> 
> Operations I'm thinking of:
> 
>   - Mail splitting.
>   - `B c' and `B m' within a server.
>   - Entering a group (ie, fetching headers).
>   - Searching in a group with `M-s'.
>   - Checking all groups when Gnus is started.  (I'm not sure what
>     happens here, but I think at least the number of unread messages
>     in each group needs to be computed.)
> 
> Feel free to add operations which I haven't thought of.
> 
> Of the above, I know nnml best, and I have seen a bit of nnfolder and
> nnmh.  But I don't know how nnfolder and nnml compare when moving
> messages between groups -- which one is faster?  I think fetching
> headers is fastest in nnml, then comes nnfolder, and then nnmh.  Is
> this correct?  nnmh seems to be very slow when Gnus is started, at
> least compared with nnml; but how does nnfolder come in?

Let's see...  This is just off the top of my head; I haven't done any
studies.  In order of speed, fastest first:

Mail splitting: nnmbox, nnbabyl, nnfolder, nnmh, nnml
Moving and copying: Er.

No, wait.  There's two kinds of speeds involved.  For instance, if you 
get one new mail, the overhead of loading the huge nnmbox mbox into
Emacs will be large, and nnmh will be fastest.  If you get a gazillion 
mails, nnmbox will still have to load its mbox, but after that, it'll
just append to its buffer, so it will be faster.

The same goes for pretty much all the other operations as well --
`M-s' in an nnfolder group is faster, but entering an nnml group is
faster than entering an nnfolder group.  And stuff.  Like.

Checking groups on startup is the same for all the mail backends
except nnmh, since they all have active files.

(And I do believe Quimby got, er, slashdotted.  I mean it only has
16MB of RAM, and each PHP-httpd takes 8MB.  Swap-o-rama.  And I
probably forgot to put a MaxClients thing into the startup file.

It had a load of 49 before it stopped talking to me.

Wait!  I got a prompt!  Yay!

I should put more RAM into the beast.)

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen