On Sat, Sep 30, 2006 at 12:16:44AM +0200, Brice Goglin (brice@myri.com) wrote:

Jeff Garzik a écrit :

quoted

Brice Goglin wrote:

quoted

This is a complete rework of the myri10ge receive path. The first
patch converts skb allocation to use physical pages. The second one
adds a software implementation of Large Receive Offload. The third
one updates the driver version to 1.1.0.

The complete driver code in our CVS actually also supports high-order
allocations instead of single physical pages since it significantly
increase the performance. Order=2 allows us to receive standard frames
at line rate even on low-end hardware such as an AMD Athlon(tm) 64 X2
Dual Core Processor 3800+ (2.0GHz). Some customer might not care a lot
about memory fragmentation if the performance is better.

But, since high-order allocations are generally considered a bad idea,
we do not include the relevant code in the following patch for inclusion
in Linux. Here, we simply pass order=0 to all page allocation routines.
If necessary, I could drop the remaining reference to high-order
(especially replace alloc_pages() with alloc_page()) but I'd rather
keep it as is.

If high-order allocations are ever considered OK under some circum-
stances, we could send an additional patch (a module parameter would
be used to switch from single physical pages to high-order pages).

As Herbert's already done, I would rather let the net core people
comment on this.  The code implementation doesn't look scary, but we
may want to be smarter about this in the core net stack, rather than
implementing it inside multiple drivers.

Ok, makes sense. We look forward to see this.

Could we get patch #1 merged anyway (page-based skb allocation)?

Any comments about what I was saying about high-order allocations above?

It is quite strnage that you see very noticeble speed degradation after
switching from higher order to 0 order allocations, could specify where 
observed  bottleneck in network stack is?

thanks,
Brice

-- 
	Evgeniy Polyakov