[distcc] Suggestion about host selection

[Christophe LYON]

On 18.06.2008 17:32, Fergus Henderson wrote:
> On Wed, Jun 18, 2008 at 7:22 AM, <thomas at schuerger.com 
> <mailto:thomas at schuerger.com>> wrote:
> 
>     Hi,
> 
>     when given a list of hosts in DISTCC_HOSTS, e.g.
> 
>     DISTCC_HOSTS="host1/6 host2/2 host3/3"
> 
>     The documentation states that the hosts are given priority as specified,
>     so host1 is the preferred host. I looked at the distcc code and was
>     surprised to find that this "list of preference" is interpreted somewhat
>     differently than I expected.
> 
> 
> I think you have misread the code.
> 
> (Which distcc version are you using?  Though this code hasn't changed 
> between distcc 2.18.3 and distcc 3.0.)
> 
> The code does the following (this is in dcc_lock_one() in src/where.c):
> 
>    while (1) {
>         for (i_cpu = 0; i_cpu < 50; i_cpu++) {
>             for (h = hostlist; h; h = h->next) {
> 
> The middle loop is over slot number.  The inner loop is over hosts.
> It tries slot 0, host 0, and then slot 0, host 1, and then slot 0, host 
> 2, etc.
> before trying slot 1, host 1, and then slot 1, host 1, and then slot 1, 
> host 2, etc.
> 

Well,

I don't think Thomas has misread the code: I understand he says the same 
thing as you.
But distcc's man page says: "distcc  prefers hosts towards the start of 
the list, so machines should be listed in descending order of speed."

I understand this statement the same way as Thomas, that is: 
host0_slot0, host0_slot1, host0_slot2, host1_slot0, host1_slot1, ....
which is not what the actual code does.

Christophe