From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 23010143C63 for ; Mon, 19 Aug 2024 09:34:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724060086; cv=none; b=WEr7jbe/A+Oq2+g9tECOXFVmxcL+MI3GBsS6Z26Ab1YGe9aRXsu1AWG152/wrUQkveAfvoiPzjxPZbidY57LH9HYcdPS99lvk1PtxlMK4Ro4fzwDpjyUDGf/UPsWD/jUnWCI2T3ESojxlW5LDZExEtwvPEPKgXBXnWAjYVGVVcc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724060086; c=relaxed/simple; bh=x/4DTNok/TEYL4vZnw96JP8oUmLb+gUITpOfHEFsGJA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mlFy3aMCnyAwLRZb60BvDAFedZovpsxmypEJvWdCrhobeVRhuld/mn8CKHgO8fP+2seCLfAKTxo/ZJ7si+CzxxbOXq+lZurik61jGA3DyhB8Pj0euAT6CbE0bpCKXczrxidnBJkQTQ82bOmIMeEK6LQrqMXQB6KlPcJEtu9d+rs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lR5Onn7X; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lR5Onn7X" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 269E6C32782; Mon, 19 Aug 2024 09:34:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724060085; bh=x/4DTNok/TEYL4vZnw96JP8oUmLb+gUITpOfHEFsGJA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lR5Onn7XRA+c+Gp0BVB5KAEEpzwGeykZCUfaiTPGiTCtM+6KS79FWY+bicc+rxM9C +rhyqWblMtxcrj0CQ9xWEsIXhZXu5s1bo+lD/uZroWyLz2nNYXBLTjTm2coRhUR/Ba FtTTByyITujij38cOFWfEhdQN1KmQx1nQVVpsevgCgu1YPnu8fERRKbjrfOAWWUbUN xqsjocGDekZjl6eIqwXnNRnLZ74nPIrN/ZjJU3zFX/XfX8AxOaYoSWK2AtJkuPN92k GQKThbzjeyXrmUexuqU3WnW+EJndFxBupJ9yoiXJMe9ETrWxMqr4Wpmq5kITVVV2NB qaC9wIPTjtuDw== Date: Mon, 19 Aug 2024 10:34:41 +0100 From: Simon Horman To: Christoph Paasch Cc: netdev , Eric Dumazet , Paolo Abeni , Jakub Kicinski , David Miller , Roopa Prabhu , Craig Taylor Subject: Re: [PATCH netnext] mpls: Reduce skb re-allocations due to skb_cow() Message-ID: <20240819093441.GC11472@kernel.org> References: <20240815161201.22021-1-cpaasch@apple.com> <20240816111843.GU632411@kernel.org> <967C2745-1EDB-464E-9C80-46345CA91650@apple.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <967C2745-1EDB-464E-9C80-46345CA91650@apple.com> On Fri, Aug 16, 2024 at 03:20:03PM -0700, Christoph Paasch wrote: > Hello! > > > On Aug 16, 2024, at 4:18 AM, Simon Horman wrote: > > > > On Thu, Aug 15, 2024 at 09:12:01AM -0700, Christoph Paasch wrote: > >> mpls_xmit() needs to prepend the MPLS-labels to the packet. That implies > >> one needs to make sure there is enough space for it in the headers. > >> > >> Calling skb_cow() implies however that one wants to change even the > >> playload part of the packet (which is not true for MPLS). Thus, call > >> skb_cow_head() instead, which is what other tunnelling protocols do. > >> > >> Running a server with this comm it entirely removed the calls to > >> pskb_expand_head() from the callstack in mpls_xmit() thus having > >> significant CPU-reduction, especially at peak times. > > > > Hi Christoph and Craig, > > > > Including some performance data here would be nice. > > Getting exact production performance data is going to be a major challenge. Not a technical challenge, but rather logistically, ... Understood :)