From owner-freebsd-stable@freebsd.org Tue Mar 8 18:56:43 2016 Return-Path: Delivered-To: freebsd-stable@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 1B524AC80FA for ; Tue, 8 Mar 2016 18:56:43 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from mail.samsco.org (suzy.samsco.org [168.103.85.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id EB48710D0 for ; Tue, 8 Mar 2016 18:56:42 +0000 (UTC) (envelope-from scottl@samsco.org) Received: from localhost (localhost [192.168.254.3]) by mail.samsco.org (Postfix) with ESMTP id DF5BC15C1867E; Tue, 8 Mar 2016 18:58:36 +0000 (UTC) Received: from mail.samsco.org ([192.168.254.3]) by localhost (mail.samsco.org [192.168.254.3]) (maiad, port 10024) with ESMTP id 10538-08; Tue, 8 Mar 2016 18:58:36 +0000 (UTC) Received: from [192.168.1.85] (access-63-249-67-150.static.cruzio.com [63.249.67.150]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: scottl@samsco.org) by mail.samsco.org (Postfix) with ESMTPSA id 6D80315C1867C; Tue, 8 Mar 2016 18:58:36 +0000 (UTC) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.2 \(3112\)) Subject: Re: kernel: mps0: Out of chain frames, consider increasing hw.mps.max_chains. From: Scott Long In-Reply-To: <20160308184823.GF70809@zxy.spb.ru> Date: Tue, 8 Mar 2016 10:56:39 -0800 Cc: freebsd-stable@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20160306194555.GC94639@zxy.spb.ru> <0F0C78F4-6FE2-43BA-B503-AA04A79F2E70@samsco.org> <20160306212733.GJ11654@zxy.spb.ru> <20160307060407.GK11654@zxy.spb.ru> <5B8DD95A-9FA0-4E16-85A1-87B54035B3F7@samsco.org> <20160307111012.GL11654@zxy.spb.ru> <20160308180746.GE70809@zxy.spb.ru> <6189E959-3489-438E-8D91-9E5E46E2D482@samsco.org> <20160308184823.GF70809@zxy.spb.ru> To: Slawa Olhovchenkov X-Mailer: Apple Mail (2.3112) X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 08 Mar 2016 18:56:43 -0000 > On Mar 8, 2016, at 10:48 AM, Slawa Olhovchenkov = wrote: >=20 > On Tue, Mar 08, 2016 at 10:34:23AM -0800, Scott Long wrote: >=20 >>=20 >>> On Mar 8, 2016, at 10:07 AM, Slawa Olhovchenkov = wrote: >>>=20 >>> On Mon, Mar 07, 2016 at 02:10:12PM +0300, Slawa Olhovchenkov wrote: >>>=20 >>>>>>>> This allocated one for all controllers, or allocated for every = controller? >>>>>>>=20 >>>>>>> It=E2=80=99s per-controller. >>>>>>>=20 >>>>>>> I=E2=80=99ve thought about making the tuning be dynamic at = runtime. I >>>>>>> implemented similar dynamic tuning for other drivers, but it = seemed >>>>>>> overly complex for low benefit. Implementing it for this driver >>>>>>> would be possible but require some significant code changes. >>>>>>=20 >>>>>> What cause of chain_free+io_cmds_active << max_chains? >>>>>> One cmd can use many chains? >>>>>=20 >>>>> Yes. A request uses and active command, and depending on the size = of the I/O, >>>>> it might use several chain frames. >>>=20 >>> I am play with max_chains and like significant cost of handling >>> max_chains: with 8192 system resonded badly vs 2048. Now try 3192, >>> response like with 2048. >>=20 >> Hi, I=E2=80=99m not sure I understand what you=E2=80=99re saying. = You said that you tried 8192, but the system still complained of being = out of chain frames? Now you are trying fewer, only 3192? >=20 > With 8192 system not complained of being out of chain frames, but like > need more CPU power to handle this chain list -- traffic graf (this > host servered HTTP by nginx) have many "jerking", with 3192 traffic > graf is more smooth. Hi, The CPU overhead of doing more chain frames is nil. They are just = objects in a list, and processing the list is O(1), not O(n). What you = are likely seeing is other problems with VM and VFS-BIO system = struggling to deal with the amount of I/O that you are doing. Depending = on what kind I/O you are doing (buffered filesystem reads/writes, memory = mapped I/O, unbuffered I/O) there are limits and high/low water marks on = how much I/O can be outstanding, and when the limits are reached = processes are put to sleep and then race back in when they are woken up. = This causes poor, oscillating system behavior. There=E2=80=99s some = tuning you can do to increase the limits, but yes, it=E2=80=99s a = problem that behaves poorly in an untuned system. Scott