From owner-freebsd-stable@FreeBSD.ORG Thu May 10 16:37:10 2012 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 641CB106566C for ; Thu, 10 May 2012 16:37:10 +0000 (UTC) (envelope-from alan.l.cox@gmail.com) Received: from mail-pb0-f54.google.com (mail-pb0-f54.google.com [209.85.160.54]) by mx1.freebsd.org (Postfix) with ESMTP id 3315A8FC14 for ; Thu, 10 May 2012 16:37:10 +0000 (UTC) Received: by pbbro2 with SMTP id ro2so2481424pbb.13 for ; Thu, 10 May 2012 09:37:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:reply-to:in-reply-to:references:date:message-id :subject:from:to:cc:content-type; bh=0kP9EEiI41e+nrGvrhYNEbSZuGw/o3EbnffnxtES7OE=; b=iUWRa8CgW/KU44oQQkh3Tiwa8NOCZvzCkL41wWEJyio+/vXZJZqbNaUWqt5lNgM7Na TGGgXGR3HC8gVoYR2NITk2KbucpPZ3K0qUdNkmL4I5ScnFCnB69s3fWr2nEo1iGoe68Q ZDUbPEvd8horBNZf/23DYD73BiF+poXp4FZq7CYN32UwH/sJNOg+b30XMTr+lqyXP2fG UrNyy4TebQGDeAwgvvO/Qx2fVv2OTZu8weNWXqw7oFJbqXzKlMjyL24sVMAuf4eR/0Rr fW5sbtdxi85veqbVVxJTYxTKkbT1E2R1983o3g2O9arz+3vwSCyI3oiN5wW4bZNplvAK ZLSw== MIME-Version: 1.0 Received: by 10.68.190.7 with SMTP id gm7mr21443739pbc.156.1336667828217; Thu, 10 May 2012 09:37:08 -0700 (PDT) Received: by 10.68.63.199 with HTTP; Thu, 10 May 2012 09:37:08 -0700 (PDT) In-Reply-To: <4FABE440.5000100@greatbaysoftware.com> References: <4FAAAF8E.40007@greatbaysoftware.com> <4FABE440.5000100@greatbaysoftware.com> Date: Thu, 10 May 2012 11:37:08 -0500 Message-ID: From: Alan Cox To: Charles Owens Content-Type: text/plain; charset=ISO-8859-1 X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Adam Vande More , freebsd-stable@freebsd.org Subject: Re: superpages not solving "PV entries" limit warning X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: alc@freebsd.org List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 10 May 2012 16:37:10 -0000 On Thu, May 10, 2012 at 10:52 AM, Charles Owens wrote: > That's very helpful! I had read about that and wondered if it applied to > i386. > > Should I have expected "superpages" to completely cure the condition... or > does it just help? Should I now be looking at tuning the related pmap > sysctls to give further relief? > > Superpages won't cure the problem due to the nature of your workload. After a fork, writes to portions of the address space that are both superpages and copy-on-write will trigger demotion, or re-instantiation of the 4KB page granularity PV entries. Ultimately, repromotion to superpages may occur, but in the meantime, your peak usage of PV entries is only slightly reduced. The bottom line is that you'll need to resort to tuning. Alan