From mboxrd@z Thu Jan 1 00:00:00 1970 From: Flavio Leitner Subject: Re: RFC limit sk_mem_quantum to 8192 Date: Wed, 22 May 2013 11:31:00 -0300 Message-ID: <20130522143100.GE17292@obelix.rh> References: <20130522004541.GA17240@obelix.rh> <1369184962.3301.264.camel@edumazet-glaptop> <20130522015858.GB17240@obelix.rh> <1369189261.3301.269.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, David Miller To: Eric Dumazet Return-path: Received: from mx1.redhat.com ([209.132.183.28]:50367 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752744Ab3EVObE (ORCPT ); Wed, 22 May 2013 10:31:04 -0400 Content-Disposition: inline In-Reply-To: <1369189261.3301.269.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, May 21, 2013 at 07:21:01PM -0700, Eric Dumazet wrote: > On Tue, 2013-05-21 at 22:58 -0300, Flavio Leitner wrote: > > On Tue, May 21, 2013 at 06:09:22PM -0700, Eric Dumazet wrote: > > > > > Are you sure a network driver doesn't provide skb using a full page ? > > > > You lost me. You're saying that today we consider a page size > > a minimum and so if we reduce that, the skb wouldn't fit in the > > min sk memory? > > SK_MEM_QUANTUM is also used in UDP stack, thats why I am asking. Yeah, it is. SCTP too, but for the protocol cases, the most complex one appears to be TCP, and it doesn't seem to be a problem to replace the minimum with something not page sized. For the drivers, it seems to have an indirect assumption that page size bytes is a minimum acceptable, so changing this minimum could cause a performance issue. Well, this define is quite old, so I am not sure if there are other historical reasons to keep it page size. However, if the idea of fixing SK_MEM_QUANTUM to 4k seems reasonable, I am willing to spend more time digging into this. Thanks! -- fbl