From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 92CDE45556; Thu, 4 Jul 2024 16:55:18 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 5CA1D410F1; Thu, 4 Jul 2024 16:55:18 +0200 (CEST) Received: from mail-pl1-f178.google.com (mail-pl1-f178.google.com [209.85.214.178]) by mails.dpdk.org (Postfix) with ESMTP id B1C7C4042F for ; Thu, 4 Jul 2024 16:55:17 +0200 (CEST) Received: by mail-pl1-f178.google.com with SMTP id d9443c01a7336-1fb05ac6b77so4136015ad.0 for ; Thu, 04 Jul 2024 07:55:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20230601.gappssmtp.com; s=20230601; t=1720104917; x=1720709717; darn=dpdk.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=nJ+0a/CMccG2G9ysD8oFV/AU+j/D74e3HV0uN/4C8qc=; b=s2lIVqfYl/aEvN7cYcdHvBlw7bgevZ68Ct7vf/SKgx5RcojXCRseQZ7nUsv0qBd5fR ncMMtZM+eOEQLeug2CBppv8/qnAWvPt+r+xxdk5wRfwSHEJDPaXTBqtx9B5UXRTxqJoT 2AjXXx0+ky9eKZyHJ3euYYe8UEXIZYLHrdFU9Fi4mDTVeIzW3XZZ0G0sA5y/qB2jWau6 ScKMxcguYA8Nixg6kNPzgp9mfvaYYbmEgm6GLLR66RuWdCSwKrSnY5xAsdA2z71YJitL tOakOSKhVnkm5ZFchdQa2PfE1TY95OjzjPiXma6lMt2NB3IhiXJURWt+9nowvruWMzxf 4Qug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1720104917; x=1720709717; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:subject:cc:to:from:date:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=nJ+0a/CMccG2G9ysD8oFV/AU+j/D74e3HV0uN/4C8qc=; b=Psi5c3hQkovNmy/65L9gLVFGQZK7vY21dUjCRDwcWESbSIYPCClWbWCiRLsk0AcSKx 92YXqYUM2cwYDuM+9wiVUfybFcbK2o1fVA7PE/qe3oXN74/nubTQFMdbdBWvqNxyxl6V IwRYJhU/8G1doYGfORLGbeWhVeXpqDoJ1wDboxpXBV3X65jmYbDJMc8o6IC3To/MxXio 1Ri6VICrJGroNo4CDQCutqA3710UVdCl5iPBhC8nyMLnlKx5HvRF1XFaTMWpdXnpx+QI RBxgTcn2iNaj24Pw7rY6yHe651NzXmip8KSMEQphw3YDh2rGrDJtxqZUZiL0xfMRo7/l esAA== X-Forwarded-Encrypted: i=1; AJvYcCVnzuPk4hgHnV0x0uaB+WQQPnaAbMgZjnE478GCx7N2XWWm0K7hF+lTDN0+WfZCnifrglX/B3D70HZv3tg= X-Gm-Message-State: AOJu0YzILvSy5m0g5NZOIQa93MauJYb4CtLTcFo+cyi9qhSz/OtTRME1 4Rt2PRdXLbWthNDj4++N4/bj1o0ckV83pB8KZ/UmgFkhllC8EWyHbwL8vsd3J3o= X-Google-Smtp-Source: AGHT+IH0DxkyYajxa/ZV5DbEbm8ih1Pnxpz/Y1PeN9UgvZeCQWCZ4KkiWPYTgspqDOYV4wD962ZlJg== X-Received: by 2002:a17:903:2a8b:b0:1f9:f559:d8c7 with SMTP id d9443c01a7336-1fb33f2e612mr16503845ad.57.1720104916553; Thu, 04 Jul 2024 07:55:16 -0700 (PDT) Received: from hermes.local (204-195-96-226.wavecable.com. [204.195.96.226]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fac10c8ba8sm124121985ad.62.2024.07.04.07.55.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jul 2024 07:55:16 -0700 (PDT) Date: Thu, 4 Jul 2024 07:55:15 -0700 From: Stephen Hemminger To: Thomas Monjalon Cc: Pavan Nikhilesh Bhagavatula , Wathsala Wathawana Vithanage , Tyler Retzlaff , Ruifeng Wang , "dev@dpdk.org" , nd , Dhruv Tripathi , Honnappa Nagarahalli , Jack Bond-Preston , Nick Connolly , Vinod Krishna , "david.marchand@redhat.com" Subject: Re: [PATCH v2 2/2] eal: add Arm WFET in power management intrinsics Message-ID: <20240704075515.75a9a0cd@hermes.local> In-Reply-To: <4208140.dumfJixkPq@thomas> References: <20240604044401.3577707-2-wathsala.vithanage@arm.com> <4208140.dumfJixkPq@thomas> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Thu, 04 Jul 2024 16:14:42 +0200 Thomas Monjalon wrote: > > > Let=E2=80=99s ask Pavan why this flag is used in cn10k driver. > > >=20 > > > From our perspective, WFE is available on all the supported arm platf= orms in > > > DPDK. > > > Therefore, RTE_ARM_USE_WFE should be treated as a flag to choose betw= een > > > WFE > > > and non-WFE code paths due to performance reasons rather than as a fl= ag > > > that indicates > > > the availability of the instruction on the target CPU. > > > =20 > >=20 > > We are using this flag to allow application to choose between WFE and n= on-WFE code path. > > The non-WFE path performs slightly better. =20 >=20 > What's the benefit of the WFE path then? WFE saves power at the expense of latency. Maybe some form of hybrid approach would work best and could be always used. For example, many implementations of mutex do a short spin poll then fall back to a waiting primitive (like futex).