From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: Re: [PATCH 0/3] A few minor clean-ups to eth_type_trans Date: Thu, 30 Apr 2015 15:35:13 -0700 Message-ID: <20150430223510.GA13111@Alexeis-MBP.westell.com> References: <20150430214917.1798.49769.stgit@ahduyck-vm-fedora22> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, davem@davemloft.net To: Alexander Duyck Return-path: Received: from mail-ig0-f173.google.com ([209.85.213.173]:37370 "EHLO mail-ig0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750839AbbD3WfR (ORCPT ); Thu, 30 Apr 2015 18:35:17 -0400 Received: by igblo3 with SMTP id lo3so26251596igb.0 for ; Thu, 30 Apr 2015 15:35:16 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20150430214917.1798.49769.stgit@ahduyck-vm-fedora22> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Apr 30, 2015 at 02:53:42PM -0700, Alexander Duyck wrote: > This series addresses a few minor issues I found in eth_type_trans that > that allow us to gain back something like 3 or more cycles per packet. > > The first change is to drop the byte swap since it isn't necessary. On x86 > we could just check the first byte and compare that against the upper 8 > bits of the Ethertype to determine if we are dealing with a size value or > not. > > The second makes it so that the value we read in to test for multicast can > be used for the address comparison. This allows us to avoid a second read > of the destination address. > > The final change is to avoid some unneeded instructions in computing the > Ethernet header pointer. When we start the call the Ethernet header is at > skb->data, so we just use that rather than computing mac_header, and then > adding that back to skb->head. Great stuff! Excellent optimizations. Only the comment 'ETH_P_802_3_MIN is aligned to 512' through me off. It's divisible by 256 that matters.