From owner-freebsd-arch@freebsd.org Fri Oct 20 16:31:19 2017 Return-Path: Delivered-To: freebsd-arch@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 81A12E3A324 for ; Fri, 20 Oct 2017 16:31:19 +0000 (UTC) (envelope-from bcketchum@gmail.com) Received: from mail-it0-x22d.google.com (mail-it0-x22d.google.com [IPv6:2607:f8b0:4001:c0b::22d]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4A22881C0F for ; Fri, 20 Oct 2017 16:31:19 +0000 (UTC) (envelope-from bcketchum@gmail.com) Received: by mail-it0-x22d.google.com with SMTP id 72so14616087itl.5 for ; Fri, 20 Oct 2017 09:31:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=wzpJEVlZTIQyXTP+NqJt707NagrkFX12/3KKSH66Mag=; b=e/GUuD2FXdXKxqhWaiVCRaBbLdWMBaNKj6ZRhCcuC1NwjsXgLMvQkmpGNBZgJXvchL MOSONRwSQsMLUzDu0O/e2ZbqZUG7lNEZM1+nC6kalU1rjLMl4mX3Q6lbvK8sHUkUe2dZ WboQ91qo7XNz+4Oez8+ib7EuM8aTqdfDH57XfO9Tev+Mbs/GiEqeeJf/2GXJ04Ad16Yn CQUDU3RmYSRIL9SuIWNPfUk6jxIxHMIDPuJFi4i2Z4qTPKkue27sxJG+GmUXwCv//ZV2 1YNjfLZOMHwJ5KvD0uN5rlVWt16+sBElig6a+VnZ5M5UxgsmwAa+4PhQ5kYHaJAT2Bvy 6faw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=wzpJEVlZTIQyXTP+NqJt707NagrkFX12/3KKSH66Mag=; b=C/FQi4bB7ODgcLmr+DtBAqSMvb7DTv55BVA7HaNTIx72GWBvhdP3rLEoYkj+ryoRKG NN8+P0zp1qroZareXMdJDapeR0X5aEAIwE2en+GboHqDSbzuuCmMYoy4APPltdWUxqsr gFoTg3+kZFI1hn/KkjVI+9xP/Pb116SWOGsF4lWbOmWh2Z1O1kPgNyxGw/JoLAw//3Ei bhRi3AkYCKR5jM3PUfcRC94dDKQUsfY6QYIsp1BAR7rDC3nnHb6bZ3W2OO9seCP6Ipkm ELZuK3BGKV+mlPZWRJWDPCFbgseyI692UOUUD4uNDG1HBE1PE+NHzFaudKIR4Cb0O8F7 FbmQ== X-Gm-Message-State: AMCzsaVdhGZ54G79SCq8/mRDCHdXOh3O0sMocHzy/QJqG6174M0+PK3f zLMWp5LmJ/qfBaCOPGmvO6iqXpqArYgMVFqjzFKrHw== X-Google-Smtp-Source: ABhQp+S+oyyD9PmIOQaK6ioKJ1ctWGgvJvQe60Q8llElgL5z2bjhJisAwucGytYAKkEXpo2vvh7Ph5UDyjxxBwNWFIQ= X-Received: by 10.36.93.84 with SMTP id w81mr3429021ita.139.1508517077531; Fri, 20 Oct 2017 09:31:17 -0700 (PDT) MIME-Version: 1.0 Received: by 10.107.1.151 with HTTP; Fri, 20 Oct 2017 09:31:16 -0700 (PDT) In-Reply-To: References: From: Bret Ketchum Date: Fri, 20 Oct 2017 11:31:16 -0500 Message-ID: Subject: Re: PEBS support in hwpmc To: freebsd-arch@freebsd.org Content-Type: text/plain; charset="UTF-8" X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 20 Oct 2017 16:31:19 -0000 PEBS records do capture callchain-like infromation. I'm most interested (currently) with FRONTEND_RETIRED, MEM_LOAD_RETIRED and MEM_LOAD_L3_HIT_RETIRED. Which require understanding of sub-events. These counters can be used to differentiate the myriad of Front-End/Back-End bound issues before drilling down to offending code fragments. On Fri, Oct 20, 2017 at 9:24 AM, Ryan Stone wrote: > On Fri, Oct 20, 2017 at 7:27 AM, Bret Ketchum wrote: >> Without this support (or a VTune subscription) understanding >> Front-End/Back-End bound applications running on Skylake/Kaby Lake >> processors will be difficult at best > > I'm afraid that I don't know of any work related to PEBS in hwpmc. > However, I'm curious as to why PEBS is so important on these > architectures. My experience with hwpmc profiling has been that > callchain information is frequently critical for understanding the > performance characteristics and my understanding is that PEBS by > design cannot capture that information.