From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj2-f12.google.com (mail-pj2-f12.google.com [74.125.227.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 57FE6286D5E for ; Mon, 21 Sep 2026 00:57:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.227.140 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789952268; cv=none; b=YOOky7TNdeTCbvRQ1vRgTqVxSyFfAihJC7WUk+dtpJjBsScxw7cCQMAvMHW7nCivqfPBiI1llifejG9nYwHYcVoBSCmciKBGAJvB3sKJWJxKyzEPChitKBiFpKZ5jRPhBy+XaJY7iivuwrjyCOa29R46foUX+Fav0ORRv/oliW0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789952268; c=relaxed/simple; bh=C60AjUAEpXim1Lx1Qg54EvmPDrGaeVF56MRd17p2Mhg=; h=Content-Type:Date:Message-Id:Cc:Subject:From:To:In-Reply-To: References:MIME-Version; b=DM1J6ETk1BzZEbLQVM1DdguM2oN7LrrCIb+za2NssajlKXjB4H7ymLTZh4JfZpq8QWMF0k25x/NGBATLUp7wMVuDOaYLtOM71p8c9WAc/89P60seXOFFQergGoxJ5GziWysXbpnYHS3ac2Q96GXZGPVo31OOFJuV/e01Xxbuha8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=tGx/2mpm; arc=none smtp.client-ip=74.125.227.140 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="tGx/2mpm" Received: by mail-pj2-f12.google.com with SMTP id 98e67ed59e1d1-396cccbba91so1626746a91.1 for ; Sun, 20 Sep 2026 17:57:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1789952267; x=1790557067; darn=vger.kernel.org; h=mime-version:content-transfer-encoding:references:in-reply-to:to :from:subject:cc:message-id:date:content-type:from:to:cc:subject :date:message-id:reply-to:content-type; bh=roGaqM7NVQofKofPOYKwFYhGCB8RP3HE83QmkgW8dwo=; b=tGx/2mpm6DLNIb89ROHoLk1IHMN817JS9Cmppow7JhJ/TXF8uCICn8fCp/iFYhPvAW p8u4Vv9Qm7dLb2+6SxkEf6pxZeHRpjv96iKkyUh/pRlLbeEmJGEeRnXza4/l14JuYeoa y8WomtMS/vUj37OVPaaU+0otbvNd1kyxOY1NPgPoz5/mFrfohNGAV4u0Wo7TctVfmi0P 0T/dhuNCdc9vb9UKD2e6TOypaP9J2OkFqpk22eRdGZZbSkVFYK1pc06LTY+M2+DHAkad CAk4vOHDPldzE8xJoNkb93VozLsTgvB6L9DbEGpz5yDp2oFdNPdIoE57dgndKJk7r8pm 0J0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789952267; x=1790557067; h=mime-version:content-transfer-encoding:references:in-reply-to:to :from:subject:cc:message-id:date:content-type:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=roGaqM7NVQofKofPOYKwFYhGCB8RP3HE83QmkgW8dwo=; b=ECpp34bu5qipRrhtxbGaSfhb1d/uPwLP0gkEg+RxFQl3E5EYASgo9h/kE46yO5X4zB xZr6F5dfdSJfsQtC3r7d5SPk0Pw6yQzRWpIJGZ3Lklw9ZlD58MMzWDiPWvboE9Kbn5fV ZMffOv9K0WNj2Qx4wQRxz5Ff9TyscACKbpXjTgJLdW+wadCEQW8/Az/vsHYQwYGbUS36 rX38tcoL9vuR53TMluQH7/fmgi+k7PAgdoiQw8Owsmy+eIiNlJ+/t9NwBfcobkQUaDZT QPyR9HGxOmeD1EtCC76Youht5+ElZ+Scgx/8z/LFX5P/gjU4LVMvpX9HadSpWu7vc44E 3ECw== X-Forwarded-Encrypted: i=1; AKwUvBx0EQsYmbtJO7+M1yPgZKKnBJx5G0g4JP9qCEV2NH/uP29cu9kBC1hYMW5rl+YUXNpn0tCSGCjVbBiqIms=@vger.kernel.org X-Gm-Message-State: AFuF++mnV0e652+t/6kvZkYAJIGdceHidG4w2j0PTsVpDwj+alinc3Ci GQb54dOT2p/Cl2d9pDO0+bhF5LavzTE4ZNMvPC9an0flGmlJXiJx5dxI X-Gm-Gg: AYBFou2bFjWIDYfC/YaRG/HKG8Lcvw0jf2KWxst6qy2PUYLBjPXcoQfjR9rrHwMpOmC uuUpvuru2stxeAbLBNGJiijGe2noI/VYI5RQvsExHJNRAnon/wEHHDDShe4fI4ydw/NAsCq7VMp 0PSGE0E9ems7ccAoGIVJ0scMvISQ/jb4ltf+0VY+ebNYpTGUY8ExNIHdFo4kIBLSZfkvKbAkTS1 gsw7OWGO6ALXt/yIvNrOvBOB0I9KydxnnwZnMSIrUjcSzjFFDarK4KUW/fRGcooZ65gCOTY6/SQ tANggf4lt8Z3Z8CsUQDk1K5SF4wiJepXToJpV/IXdLoju21qa3IxKezycIwSDgVQQ0Pf0Rhx0+W yiAxpj6vQaNz4spHWev+Iq6vEPfJNgMGVpXU6qzn2C4Cvuf7Pfh3GKkKwu+9L50rNVsqp6uL7nS 3NXShdAA1iCi+ukr85dsRGM8w1ddadj5goY1vqgerCja2DjRvtnzoOS9KNgs1WWK9KRO4W/bTOT cHPabVxboOAahRMsHy+PVaT+aLUeEdGYidixiZafvMw6E8UexNvlpeviGQ5DDDXgxLl7FBfKUo9 8Zg= X-Received: by 2002:a17:90b:56c5:b0:39e:4c81:6c66 with SMTP id 98e67ed59e1d1-39e54dc1a3emr14850525a91.33.1789952266591; Sun, 20 Sep 2026 17:57:46 -0700 (PDT) Received: from localhost ([153.61.198.252]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39e6c4ba12csm11280817a91.11.2026.09.20.17.57.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 20 Sep 2026 17:57:46 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Mon, 21 Sep 2026 00:57:45 +0000 Message-Id: Cc: , Subject: Re: [PATCH bpf-next v5 2/2] bpf: htab: Reduce elem_size by 8 bytes for small key sizes From: "Alexei Starovoitov" To: "T.J. Mercier" , , , , , , , , , , , In-Reply-To: <20260921002206.184660-3-tjmercier@google.com> References: <20260921002206.184660-1-tjmercier@google.com> <20260921002206.184660-3-tjmercier@google.com> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sun, Sep 20, 2026 at 05:22 PM T.J. Mercier wrote: > + l = __lookup_elem_raw(htab, head, hash, key, key_size, &n); > + if (l) { > + /* > + * Pairs with smp_wmb() in alloc_htab_elem() to ensure > + * value/pptr reads happen after key/hash match on > + * recycled elements. > + */ > + smp_rmb(); > + return l; > + } Is this AI suggestion to add barriers? I think it should be on the program side. If users really care then they will add such barriers. Doing it unconditionally will cost performance for everyone. Especially on arm64. If you disagree, please provide ./bench bpf-hashmap-lookup numbers on arm64 to demonstrate that perf is the same. pw-bot: cr