From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <3A37A048.46E692A0@mvista.com> Date: Wed, 13 Dec 2000 11:14:00 -0500 From: Dan Malek MIME-Version: 1.0 To: Graham Stoney CC: Brian Ford , linuxppc-embedded@lists.linuxppc.org Subject: Re: 2.5 or 2.4 kernel profiling References: <20001212182856.A8336@brixi.research.canon.com.au> <20001213121554.B17129@brixi.research.canon.com.au> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Graham Stoney wrote: > This does indeed sound better; the only sticky part I can think of is setting > the FCC/FEC to keep giving you Rx interrupts even when there are no buffer > descriptors to put the incoming packets in, Although I have not yet proven this, I am leaning toward the following. Allocate a small fixed set of receive buffers (like we used to do) in the driver and mark them copy-back cached. The received BDs will always point to thesed buffers. Then, copy-and-sum these into IP aligned skbuffs. The advantage of Graham's DMA into skbufs isn't that the driver doesn't copy/sum, it is that later when the IP stack does it we get burst transfers into cache. So, we get this advantage plus the IP packet aligned properly for the remainder of the stack. Of course, the downside of this is the receive buffers are one-time cached. We blow the cache away to make the TCP benchmark look good, and the remaining applications suffer. I still have a problem with this.....making single focused benchmarks look good isn't necessarily the best for the overall system application. -- Dan ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/