Finding a more elegant solution to the deadlock issue in Ethernet
drivers was my original reason for trying this out. But the (yet
somewhat unverified) performance increase is a bonus.
I mentioned both advantages in the submitted patch.
I have not yet done any performance measurements. It is sifficult to
measure this particular optimization, since it cannot be measured as a
decreased latency between two events.
Instead, the number of CPU cycles spent per second for a certain traffic
load must be measured. A much more difficult measurement...
I would need to find a way to produce a perfectly controlled traffic
load, and then measure the exact CPU load.
The patch decreases the amount of code executed in the processing of a
pbuf, so there should be a performance increase. But it might not be a
big difference.
Regards,
Timmy Brolin
On 3 nov 2011 17:15 "Bill Auerbach" <[email protected]> wrote:
>
> Simon,
>
>
>
> I commented based on the “This should improve performance”statement in
> Timmy’s message. The intent was not to invalidate the change or deem
> it unnecessary, only to not have performance be a reason one heads off
> in the direction of adding this feature to their port. I well could be
> wrong about performance too – this is merely an opinion based on code
> review.
>
>
>
> Bill
>
>
>
> From:[email protected]
> [mailto:[email protected]] On
> Behalf OfSimon Goldschmidt
> Sent: Thursday, November 03, 2011 9:47 AM
> To: Mailing list for lwIP users
> Subject: Re: [lwip-users] Automatic Rx DMA ring replenish
>
>
>
> "Bill Auerbach" <<[email protected]>>:
>
> > I haven’t benchmarked to be able to provide factual data, but I’ve
> > done a lot of optimization and tweaking of lwIP to improve bandwidth
> > and my study of pbufs and memory pools did not show the need for
> > improvement considering all of the other things required to handle a
> > TCP connection.
>
>
>
> I saw the patch not as speed optimization but as a way to simplify the
> netif driver: to provide a robust implementation, a netif driver would
> have to ensure it retries if pbuf_alloc fails because the pool is
> empty (to prevent a deadlock). This patch prevents a netif driver
> having to implement some sort of timer because it just gets notified
> when pbufs are available again.
>
>
>
> Simon
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