From owner-freebsd-arch@FreeBSD.ORG Sat Apr 25 17:18:52 2015 Return-Path: Delivered-To: freebsd-arch@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 087FBB5D; Sat, 25 Apr 2015 17:18:52 +0000 (UTC) Received: from mail-ob0-x234.google.com (mail-ob0-x234.google.com [IPv6:2607:f8b0:4003:c01::234]) (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 C420415BC; Sat, 25 Apr 2015 17:18:51 +0000 (UTC) Received: by oblw8 with SMTP id w8so58303781obl.0; Sat, 25 Apr 2015 10:18:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=CTYhs4OypYpVi3j7BMK9kWple/ceHM1m2PNQPZg8kYk=; b=FV9ddbafZRJEZVykE+HP6mZQkFtr6UwNKt5RJ7cqoz3/bu7I/JwnGlIXdF7POzGru1 Zu3wCRmdzVaTnAvrCIgfpqHOj+lBTpKxgXG2SuT0YGe5GRg2G7Wz28B1QVo2PwjkNYMR WPaqttoxYwA7rxLRyf7FUsheiR9KWg+0QfvO1camilvIj9/c9AxHdwvmiYJ832DDqyr+ Az022rzZqILsdLOHd2ETm2dwwyjfFH+UdqaoQpA6wNm8js1by6jTLH75BqXmOdB56xaO 6/iFA1yo4FDnpJU14Ez3vSVgOc9jV+Ip7F/BEFSG4Jc4L3en0sWIA8oPqMPNusZMY/D1 j0MQ== MIME-Version: 1.0 X-Received: by 10.202.186.214 with SMTP id k205mr3329740oif.10.1429982330879; Sat, 25 Apr 2015 10:18:50 -0700 (PDT) Sender: kmacybsd@gmail.com Received: by 10.202.11.82 with HTTP; Sat, 25 Apr 2015 10:18:50 -0700 (PDT) In-Reply-To: References: Date: Sat, 25 Apr 2015 10:18:50 -0700 X-Google-Sender-Auth: AFCAk4WZK3ZObL_e4cORbLR6tFs Message-ID: Subject: Re: RFC: setting performance_cx_lowest=C2 in -HEAD to avoid lock contention on many-CPU boxes From: "K. Macy" To: Adrian Chadd Cc: "freebsd-arch@freebsd.org" Content-Type: text/plain; charset=UTF-8 X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 25 Apr 2015 17:18:52 -0000 Perhaps use an arbitrary cutoff - say <= 8 cores - where the cx_lowest=C3. This serialization isn't going to hurt on systems with more modest core counts. On Sat, Apr 25, 2015 at 9:31 AM, Adrian Chadd wrote: > Hi! > > I've been doing some NUMA testing on large boxes and I've found that > there's lock contention in the ACPI path. It's due to my change a > while ago to start using sleep states above ACPI C1 by default. The > ACPI C3 state involves a bunch of register fiddling in the ACPI sleep > path that grabs a serialiser lock, and on an 80 thread box this is > costly. > > I'd like to drop performance_cx_lowest to C2 in -HEAD. ACPI C2 state > doesn't require the same register fiddling (to disable bus mastering, > if I'm reading it right) and so it doesn't enter that particular > serialised path. I've verified on Westmere-EX, Sandybridge, Ivybridge > and Haswell boxes that ACPI C2 does let one drop down into a deeper > CPU sleep state (C6 on each of these). I think is still a good default > for both servers and desktops. > > If no-one has a problem with this then I'll do it after the weekend. > > Thanks! > > > > -adrian > _______________________________________________ > freebsd-arch@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-arch > To unsubscribe, send any mail to "freebsd-arch-unsubscribe@freebsd.org"