From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joe Perches Subject: Re: [PATCH 1/7] [NET]: uninline skb_put, de-bloats a lot Date: Thu, 27 Mar 2008 17:54:40 -0700 Message-ID: <1206665680.4849.137.camel@localhost> References: <1206621486-5408-1-git-send-email-ilpo.jarvinen@helsinki.fi> <1206621486-5408-2-git-send-email-ilpo.jarvinen@helsinki.fi> <1206645050.4849.77.camel@localhost> <20080327.150456.39560267.davem@davemloft.net> <1206663095.4122.82.camel@calx> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: David Miller , ilpo.jarvinen@helsinki.fi, akpm@linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, acme@redhat.com To: Matt Mackall Return-path: Received: from 136-022.dsl.labridge.com ([206.117.136.22]:1249 "EHLO mail.perches.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753111AbYC1Az0 (ORCPT ); Thu, 27 Mar 2008 20:55:26 -0400 In-Reply-To: <1206663095.4122.82.camel@calx> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2008-03-27 at 19:11 -0500, Matt Mackall wrote: > In the 486 era, when CPU performance was close to 1:1 with memory, > branches were more expensive than sequential memory fetches, and > registers were scarce, inlining made a fair amount of sense. > > But now we've moved very far away from that indeed: Systems have certainly improved but Linux is used in a wide variety of CPU Hz, memory & register architectures. Some of those systems haven't changed at all. Some of those systems have sufficient cache for a networking stack. I think this change could negatively impact some of these different uses and systems. > In the case of this patch, removing 60-100k from the network stack means > we're almost certainly avoiding a lot of cache misses in the big picture > while taking a few cycle hit per packet in the smallest scale. I think the quantities of big v small are instance dependent and it might be prudent to have the capability to keep these functions inline.