From owner-svn-src-head@FreeBSD.ORG Fri Nov 21 23:26:57 2014 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id C095DB3D for ; Fri, 21 Nov 2014 23:26:57 +0000 (UTC) Received: from nm19-vm4.bullet.mail.gq1.yahoo.com (nm19-vm4.bullet.mail.gq1.yahoo.com [98.136.217.27]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 85143C4A for ; Fri, 21 Nov 2014 23:26:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s2048; t=1416612410; bh=CsUrKUZloZb85sN1GErGwcwL0lU65Na1eiw+eCbKWg8=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From:Subject; b=q491NJEVQzZEUxjFUNkZuUjfM6KSXdrL6wjsF65z4ffnho2tx2NpHTBWyJBksfC3CexWqHB6uaCuTkcPOye/SP0Fp5vRv9iQT7V59Ml44DaUWwlE0LEexqyku4tTjtDAViX2TJeR6o1gQVNSzIB9r3ReftWULQFHQsbsc/iWsSHeckuTO7jF38LiPnTPbDHtywrBT+KLgSiaAXKbdcXMBUmmpdVRbaQwehbxdElPaqWC9b+mmKiJegwMo++5usCEKGz+IPeCjDTDcKkepX9Pg4wZHo4ADPKmGZjPqQgA8vEEfSxKq6L3A6vl3gBnMHVoED9x8IBrpIG+BYJaggW1Xw== DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s2048; d=yahoo.com; b=YKonyy+ZMfzD092gHepHvkssQx+GU2B1WAeiSVZvX+xZhH9R6i33/hmO03a9WlU6Dy4KJ+j4nqdCS+hblppvx5yKm/CTlwIHub2TrKOO56/6BeK1HWEB8OMNTwnzkD9i1GXnutZGPMJlEYHYqsqrsdh7rTTfuQaRDzPiMcEQitYpxjA+nE3sShydKgi7u0Zq/fC4dq9TrvTrJG+AMjVpmAvitRkkxuvQVDsXaQq5dE60EBBA+t7ko+RuOxyTlL3MxbtzKiNDmTXQAsYlV0LrwQ1ZVctKOLqGmNAD3Wex5NRjtDxsYMaeTvtfuBL1/aLbFX0jfr0WMxEYIKnENAcxRQ==; Received: from [216.39.60.182] by nm19.bullet.mail.gq1.yahoo.com with NNFMP; 21 Nov 2014 23:26:50 -0000 Received: from [208.71.42.197] by tm18.bullet.mail.gq1.yahoo.com with NNFMP; 21 Nov 2014 23:26:50 -0000 Received: from [127.0.0.1] by smtp208.mail.gq1.yahoo.com with NNFMP; 21 Nov 2014 23:26:49 -0000 X-Yahoo-Newman-Id: 993052.746.bm@smtp208.mail.gq1.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: L0sNw.MVM1nJ8kXb7dxEfh1SJ8US8xTZw_GBjtglt8hrQXb sfu2xEPBmuNJ3zrkM61E19d1pdOIAYN_MBbAHzz5C2m1_dXTy0F19k6fGkYp dyg1G9j21_ultI5VcTetq0STaZ83l.JX0HHpa3rn3DClvsiHvl2ff3qsghhe 8ma9O5cGBqn1xpY1T23WO07VqXYxstxwA8rjwG2..aAlMD8BswMj1y8x8FH8 V11.ijjOZfWUErQBzzx5wjPvXiRJuNHalIaADvV9RGgXUoDGevF4923KGxsD GLLK2Q9D2DC.JB76qhTfRVZJKhqCciUN_dpRduUYsDkGkEtnqvP0Zp3O5JO0 CsVWACma3ip2KYo5BkXGXSYtqdFpUN4asQ8sk2MqSv3TUnM_eVNF9MAMRymq Qkh3rzr1qYkd3cdJlQ7TF2qvEO.0xcEE1uQAvuLXRqhUrKKtnJ7VjUJem3iR 4kVW_Emx5G9sbjtwFkTbL64SSHkVgs0cWDgve4m6zFcs8lSmyur8RCDg9K22 kOfFAMimJ75aZuxu_OQCHSkoDKg5qaZYihg-- X-Yahoo-SMTP: clhABp.swBB7fs.LwIJpv3jkWgo2NU8- Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.1 \(1993\)) Subject: Re: svn commit: r274489 - in head/sys/amd64: amd64 include From: Scott Long In-Reply-To: <35E5EAD8-99C1-43C0-8D01-B3B5B86ECA25@me.com> Date: Fri, 21 Nov 2014 16:26:47 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: <13EC3116-6146-42FC-8941-2C7C009224B3@yahoo.com> References: <201411132211.sADMBjP3009246@svn.freebsd.org> <35E5EAD8-99C1-43C0-8D01-B3B5B86ECA25@me.com> To: Rui Paulo X-Mailer: Apple Mail (2.1993) Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org, Scott Long X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Nov 2014 23:26:57 -0000 > On Nov 20, 2014, at 11:33 PM, Rui Paulo wrote: >=20 > On Nov 13, 2014, at 14:11, Scott Long wrote: >>=20 >> Author: scottl >> Date: Thu Nov 13 22:11:44 2014 >> New Revision: 274489 >> URL: https://svnweb.freebsd.org/changeset/base/274489 >>=20 >> Log: >> Extend earlier addition of stack frames to most of support.S. This = makes >> stack traces in KDB, HWPMC, and DTrace much more reliable and useful. >=20 > No performance differences? The kernel enables/disables the compiler = option to omit the frame pointer based on the kernel config file. If = DDB, DTrace, or HWPMC is enabled, the frame pointer is always saved in C = functions.=20 >=20 > Some of these functions are in the hot path, so if you didn't see any = performance problem, I wonder if we should disable -fomit-frame-pointer = always. That=E2=80=99s a good question to look further into. I didn=E2=80=99t = see any measurable differences with this change. I think that the cost = of the function call itself masks the cost of a few extra instructions, = but I didn=E2=80=99t test with switching it on/off for the entire = kernel. That said, I purposely implemented this as macros so it could = be easily changed in the future. If someone finds that this measurably = impacts a certain workload, I wouldn=E2=80=99t object to making it = conditional, though it does complicate any hand-written ASM code that = tries to access the stack via %esp offsets. We don=E2=80=99t have = anything like that now, but Kip was concerned enough about it in the = future that I left it enabled unconditionally. Scott