From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=none (p=none dis=none) header.from=gibson.dropbear.id.au Authentication-Results: passt.top; dkim=pass (2048-bit key; secure) header.d=gibson.dropbear.id.au header.i=@gibson.dropbear.id.au header.a=rsa-sha256 header.s=202506 header.b=SEvqyCqT; dkim-atps=neutral Received: from mail.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by passt.top (Postfix) with ESMTPS id A44185A0279 for ; Tue, 29 Jul 2025 02:32:55 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gibson.dropbear.id.au; s=202506; t=1753748965; bh=HY9DA0o0AJdSTHTzo5NMuL/tIrtsroDLt6GOpoSvX0E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SEvqyCqTI+aSvtB5JVwCvjY3qVmxMarpkBkTF2S3eoLcVWB3OOil5SU5F6HxkoxT6 aPVHRrkSWmn7VZH+CQboxxLvJV/SRczjN7o/oQCkv46l0xNgyexiIzQJGnRiBxmnN5 vKvY51DmykM3mpimxoPL5EoC50tW9+6Gus8pUxVzq8GiWPVh918g49hi1gbsJo+gT9 EelbpB1WxRyLrcltOLDX2kRo9jzvTnYpSp3kIWg7SXbSlBDhv0Lp4Udr5rI5QKsaGN TdeX0+yWGXI8F9QqE6MmOx/vNlpueZCcezygpPnLiQ1MJkiDnW9xixN0WCKVfCzmaP vkuQnSv/NoXdA== Received: by gandalf.ozlabs.org (Postfix, from userid 1007) id 4brbnd3Sp9z4x3p; Tue, 29 Jul 2025 10:29:25 +1000 (AEST) Date: Tue, 29 Jul 2025 10:32:26 +1000 From: David Gibson To: Eugenio Perez Martin Subject: Re: [RFC v2 10/11] tap: add poll(2) to used_idx Message-ID: References: <20250709174748.3514693-1-eperezma@redhat.com> <20250709174748.3514693-11-eperezma@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="LpstDm1+zDl/yTUy" Content-Disposition: inline In-Reply-To: Message-ID-Hash: 6Z2EDLBKUHXLQ3PKS5FNSGU5IKX3CDI7 X-Message-ID-Hash: 6Z2EDLBKUHXLQ3PKS5FNSGU5IKX3CDI7 X-MailFrom: dgibson@gandalf.ozlabs.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top, jasowang@redhat.com X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: --LpstDm1+zDl/yTUy Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Jul 28, 2025 at 07:03:12PM +0200, Eugenio Perez Martin wrote: > On Thu, Jul 24, 2025 at 3:21=E2=80=AFAM David Gibson > wrote: > > > > On Wed, Jul 09, 2025 at 07:47:47PM +0200, Eugenio P=C3=A9rez wrote: > > > From ~13Gbit/s to ~11.5Gbit/s. > > > > Again, I really don't know what you're comparing to what here. > > >=20 > When the buffer is full I'm using poll() to wait until vhost free some > buffers, instead of actively checking the used index. This is the cost > of the syscall. Ah, right. So.. I'm not sure if it's so much the cost of the syscall itself, as the fact that you're actively waiting for free buffers, rather than returning to the main epoll loop so you can maybe make progress on something else before returning to the Tx path. --=20 David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson --LpstDm1+zDl/yTUy Content-Type: application/pgp-signature; name=signature.asc -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEEO+dNsU4E3yXUXRK2zQJF27ox2GcFAmiIFpkACgkQzQJF27ox 2GcgyRAAgsQZQmoBCDedfr7h6V8RiwyMy3utT6J51NMYjNY7V6JI/h/MNf7YvVlZ V7ZS9tlPSAPc8mEO2PJw1lTXVWvwnPCTHHV094wTw0fUCtcZGSBXdZh3HgabdB30 ayoZO0ewodKDg3/Z44h9gBUabg05GmgzLOh0gU3QAam0MULsYwg95f+5bMrbE5Ck PGR9XTQJb2JI2d1nRgb0k+xbkav0aj/c3CFbz+ZakKtL3QLjpqOXSxTu65e+32JF mm5fU4yKimNhBy8o7Bthw1vJsYnbgkRpnBVt0MOmhOR8Fremw9o+WI+HMbcG4FcH R9O/175+3JVqbKrhu7qqbsleu2cMFKUCDkFVnKD5RLsQTKakUcqAoiROtP/46dkW 4TpNxilZyDeWwe/fjf7N93XcuOFise8VfFhdfTwAVWkRWd1tV5mycrrLwpgyhd46 +n/wmVpY8Kff7agiB+f6lz/AZ8q1W1NfFKa/xvCc5g64/U2Lw/HxaPNNiNtubOyl ZfTgW0OR3kTa999MySLIPZ6K9GU09fevotcWfANRsi5V/2VeJ1JZUXkKSehctV2Z g8tIgXBSHag/YeHlaVkuHmAvEv7lRWo8nCfk2cAOzqKKB+phHFk17wcN1XG0NI/+ KmpuXuMjL2AR4olaWZozgnx8L/6PU12ahzohWEFJpv1Gu5amX4c= =5qky -----END PGP SIGNATURE----- --LpstDm1+zDl/yTUy--