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Date: Thu,  5 Jan 2006 00:42:35 +0000
From: gerry@everythingsucks.co.uk
To: dev@apr.apache.org
Subject: Re: UPDATE: [Patch] poll/unix/poll.c:apr_pollset_poll()
	optimisation
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Quoting Garrett Rooney <rooneg@electricjellyfish.net>:

> Um, I don't think that's going to work, rv is the number of
> descriptors that hit, there's nothing that says that if N hit it'll be
> the first N...

That would be true were I comparing  I<RV but I'm comapring J<RV :D

> As for the other version of this patch, I'm kind of curious if it's an
> actual improvement.  Sure, you can bail early, but at the cost of
> intruducing an extra if into each of the iterations before you bail.
> Is that actually better in the average case?

Yeah I kinda thought the same thing, was bugging me which is why I 
revisited it.

G


> On 1/4/06, gerry@everythingsucks.co.uk <gerry@everythingsucks.co.uk> wrote:
>> Greetings,
>>
>> There's a sneakier (and pretty obvious, once you look at it) way of
>> improving this loop which I prefer to my original mail by replacing the
>> for-loop condition.
>>
>> Should be safe: I like poll()... he has an honest face... I don't think
>> he will lie to us about the number of signalled descriptors.
>>
>>
>> --- poll.c      2006/01/02 18:30:27     1.1
>> +++ poll.c      2006/01/05 00:11:36
>> @@ -254,13 +254,13 @@
>>          return apr_get_netos_error();
>>      }
>>      if (rv == 0) {
>>          return APR_TIMEUP;
>>      }
>>      j = 0;
>> -    for (i = 0; i < pollset->nelts; i++) {
>> +    for (i = 0; j < rv; i++) {
>>          if (pollset->pollset[i].revents != 0) {
>>              pollset->result_set[j] = pollset->query_set[i];
>>              pollset->result_set[j].rtnevents =
>>                  get_revent(pollset->pollset[i].revents);
>>              j++;
>>          }
>>
>
> Um, I don't think that's going to work, rv is the number of
> descriptors that hit, there's nothing that says that if N hit it'll be
> the first N...
>
> As for the other version of this patch, I'm kind of curious if it's an
> actual improvement.  Sure, you can bail early, but at the cost of
> intruducing an extra if into each of the iterations before you bail.
> Is that actually better in the average case?
>
> -garrett
>