From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Woodhouse Subject: Re: [PATCH] solos-pci: Increase headroom on received packets Date: Wed, 16 Sep 2015 12:32:03 +0100 Message-ID: <1442403123.131189.70.camel@infradead.org> References: <1442399145.131189.56.camel@infradead.org> <1442400813.4116.48.camel@edumazet-glaptop2.roam.corp.google.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-BFe33wr0ldAIJTvsYgEd" Cc: netdev@vger.kernel.org, simon@fire.lp0.eu, guy@traverse.com.au, linux-atm-general@lists.sourceforge.net To: Eric Dumazet Return-path: Received: from casper.infradead.org ([85.118.1.10]:51706 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750989AbbIPLcI (ORCPT ); Wed, 16 Sep 2015 07:32:08 -0400 In-Reply-To: <1442400813.4116.48.camel@edumazet-glaptop2.roam.corp.google.com> Sender: netdev-owner@vger.kernel.org List-ID: --=-BFe33wr0ldAIJTvsYgEd Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2015-09-16 at 03:53 -0700, Eric Dumazet wrote: > You should use netdev_alloc_skb() : This helper is better for rx skbs, > as it allows for better packing of frames in GRO or TCP stack. OK, thanks. I don't have a netdev (this is an ATM device) but I can use dev_alloc_skb(). > Also netdev_alloc_skb_ip_align() might handle the NET_IP_ALIGN stuff > for arches that care. I'd briefly considered NET_IP_ALIGN but decided against it because this isn't Ethernet and my hardware header is a nice sane 8 bytes, not 14. But actually, the primary use cases for this are PPPoATM =E2=80=94 with 2 b= ytes of PPP frame type, and PPPoE over BR2684 =E2=80=94 with 14 bytes of Etherne= t header. So NET_IP_ALIGN would actually make sense. Unfortunately the FPGA can't do DMA to unaligned addresses, so I can't do it in the DMA case. I can do it for the MMIO code path though (which I still haven't tested). I'll send a new patch in a moment... --=20 dwmw2 --=-BFe33wr0ldAIJTvsYgEd Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIISjjCCBicw ggUPoAMCAQICAw3vNzANBgkqhkiG9w0BAQUFADCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0 YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcx ODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENB MB4XDTE1MDUwNTA5NDM0MVoXDTE2MDUwNTA5NTMzNlowQjEcMBoGA1UEAwwTZHdtdzJAaW5mcmFk ZWFkLm9yZzEiMCAGCSqGSIb3DQEJARYTZHdtdzJAaW5mcmFkZWFkLm9yZzCCASIwDQYJKoZIhvcN AQEBBQADggEPADCCAQoCggEBAMkbm9kPbx1j/X4RVyf/pPKSYwelcco69TvnQQbKM8m8xkWjXJI1 jpJ1jMaGUZGFToINMSZi7lZawUozudWbXSKy1SikENSTJHffsdRAIlsp+hR8vWvjsKUry6sEdqPG doa5RY7+N4WRusWZDYW/RRWE6i9EL9qV86CVPYqw22UBOUw4/j/HVGCV6TSB8yE5iEwhk/hUuzRr FZm1MJMR7mCS7BCR8Lr5jFY61lWpBiXNXIxLZCvDc26KR5L5tYX43iUVO3fzES1GRVoYnxxk2tmz 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