On 11-Apr-01 Alfred Perlstein wrote:
> * Doug White <[EMAIL PROTECTED]> [010411 16:07] wrote:
>> On Tue, 10 Apr 2001, Alfred Perlstein wrote:
>>
>> > Basically, when apache is listening on multiple IPs/ports it needs
>> > to select() on several filedescriptors. The problem (under FreeBSD
>> > at least) is that whenever you have some process select()'ing on
>> > a descriptor and another process wants to do the same you get a
>> > "select collision", a collision requires that all processes waiting
>> > on the same select channel wake up then reassert thier desire to
>> > select. So... if you have 500 apache processes select()'ing and
>> > one wakes up to service a request, finished serving, then goes to
>> > select again, all the rest (499) have to wake up and reaffirm thier
>> > desire to select().
>>
>> We haven't applied wakeup_one() to select() yet? (I think I've argued
>> about this before.)
>>
>> Someone get cracking! :)
>
> I'm not sure it's possible without redesigning the way select works.
Select does a wakeup_one() if there's not a collision on a fd. If there is a
collision, you need to do a full wakeup() since wakeup_one() on &selwait could
easily just wake up a process waiting on some other fd and not a process
waiting on the fd in question. xref. sys/kern/sys_generic.c, specifically
selrecord() and selwakeup().
--
John Baldwin <[EMAIL PROTECTED]> -- http://www.FreeBSD.org/~jhb/
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