Re: [Exim] Copy of outgoing messages to other mail

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Lähettäjä: Philip Hazel
Päiväys:  
Vastaanottaja: John W Baxter
Kopio: Exim Users
Aihe: Re: [Exim] Copy of outgoing messages to other mail
On Fri, 13 Oct 2000, John W Baxter wrote:

> Speaking of that, what is the current wisdom as to roughly where the
> boundary between "short" and "not short" falls for an alias file for Exim?


It will depend on your OS, your DBM library, and your file system's
block size, I imagine.

I've just done a trivial test. I created an alias file containing 286
entries. Each key was 4 characters long. I used "exim -be" to expand the
string "${lookup{something}...." 10 000 times. Actually, to circumvent
Exim's caching, I looked up two different keys, alternately. I used two
keys from the middle of the list, to simulate the average case for the
lsearch. This was on a Sparc Ultra 1 running Solaris 8. I repeated using
DBM (ndbm on Solaris) and cdb, and repeated for different numbers of
keys in the file. The results were as follows (real/user times, as given
by the "time" command):

#keys    LSEARCH     DBM       CBD
286      6.0/5.4   2.5/2.4   1.0/0.9
186      4.5/3.9   2.1/2.0   0.9/0.9
 86      3.1/2.6   1.8/1.7   0.9/0.9
 40      2.5/2.0   1.5/1.5   0.9/0.9
 20      2.0/1.5   1.5/1.4   0.9/0.9


I've previously waved my hands and said "between 20 and 50", and this
simple test is in that ballpark. It does show the benefit of cdb,
though, doesn't it?

-- 
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.