From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [Xen-devel] [PATCH 5/6] xen-netback: coalesce slots before copying Date: Tue, 26 Mar 2013 11:06:23 +0000 Message-ID: <5151812F.3080905@citrix.com> References: <1364209702-12437-1-git-send-email-wei.liu2@citrix.com> <1364209702-12437-6-git-send-email-wei.liu2@citrix.com> <5150699C.6080209@citrix.com> <51507C9B.3080109@citrix.com> <51509789.8090608@citrix.com> <20130325190911.GC7004@zion.uk.xensource.com> <6035A0D088A63A46850C3988ED045A4B3880B43D@BITCOM1.int.sbss.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Wei Liu , Ian Campbell , "konrad.wilk@oracle.com" , "netdev@vger.kernel.org" , Wei Liu , "xen-devel@lists.xen.org" , "annie.li@oracle.com" To: James Harper Return-path: Received: from smtp.citrix.com ([66.165.176.89]:37887 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753717Ab3CZLG0 (ORCPT ); Tue, 26 Mar 2013 07:06:26 -0400 In-Reply-To: <6035A0D088A63A46850C3988ED045A4B3880B43D@BITCOM1.int.sbss.com.au> Sender: netdev-owner@vger.kernel.org List-ID: On 26/03/13 10:52, James Harper wrote: >>> It's not clear why 19 or 20 were suggested as possible values. >>> I checked back to 2.6.18 and MAX_SKB_FRAGS there is >>> (65536/PAGE_SIZE + 2) >> >> Because the check is >= MAX_SKB_FRAGS originally and James Harper >> told me that "Windows stops counting on 20". >> > > I've obviously not been clear enough here... GPLPV stopped counting > at 20 (only needed to know if <20 or not). Windows itself can submit > a packet to NDIS with hundreds of buffers. It doesn't really matter > if it's 21 or 1021, I just didn't want to be misquoted. This still isn't clear. What's the maximum number of ring entries that GPLPV driver will use per packet? Are you saying it's 20? If so how has the GPLPV driver ever worked well with Linux's netback (with its historical limit of 18)? David