Re: socket buffers and condition variables

On 28-May-2002 Alfred Perlstein wrote:
> * John Baldwin <[e-mail]> [020528 13:21] wrote:
>> 
>> On 28-May-2002 Jeffrey Hsu wrote:
>> >   > Reduce contention upon locking a socket buffer by replacing tsleep() and
>> >   > wakeup() with a condvar.
>> > 
>> > I'd prefer if we waited until we had the networking stack all locked up
>> > before measuring and deciding that there is enough contention on socket
>> > buffers to warrant this change.
>> 
>> I don't really see how this change avoids contention anyways.
> 
> The stuff we talked about... using the mutex associated with the
> condvar rather than the schedlock to protect the cv's wait queue.
> Basically reduce contention on the global wait queues and schedlock.

Hmm, well, that won't be a valid assumption for bug so long anyways as
cv's wont' have their own queue forever but will probably share their
queue's with tsleep in the future.  It's an implementation detail.
I don't care if you use cv's instead of sleep/wakeup since cv's are
often used with mutexes, but reduced contention isn't really a valid
reason to use them.

-- 

John Baldwin <[e-mail]>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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