From owner-freebsd-hackers@FreeBSD.ORG Sun Jun 28 22:16:02 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id B52031065670 for ; Sun, 28 Jun 2009 22:16:02 +0000 (UTC) (envelope-from alan.l.cox@gmail.com) Received: from mail-yx0-f181.google.com (mail-yx0-f181.google.com [209.85.210.181]) by mx1.freebsd.org (Postfix) with ESMTP id 6CE578FC16 for ; Sun, 28 Jun 2009 22:16:02 +0000 (UTC) (envelope-from alan.l.cox@gmail.com) Received: by yxe11 with SMTP id 11so3211201yxe.3 for ; Sun, 28 Jun 2009 15:16:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:reply-to:in-reply-to :references:date:message-id:subject:from:to:cc:content-type; bh=a+jWFGK6f2IkXArxyaZVqY5AzJ9vy7k0RBULVzImqO8=; b=pc8CwIKxcQU+A3ZnZoC+YGM+b/nPjO9j65YXemVMifLoVPlMJziZ4KBcKMneJYXzP1 XXI+DFbFoKYb/2969C9CZ9MWyPF3V2HN9XmSX4uRtb+E0pGh2NsmFjigdEQJ+oClmmUx 59jjhwsWDkwFLOgI2rJP7y61ypG4yagEUotx8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:reply-to:in-reply-to:references:date:message-id :subject:from:to:cc:content-type; b=GuPu3mNMBZvHw4cEVklL+QMTUnw7LJlJ0NJ8t4nozrVgKlWdEpSBDTVw5BwT2oH+uh gcWbXdN16mb/1K/xH01KeJMwExhkWqxONE6OqMZIefrQRqFydahD5/whYWV80GPNfopX MjCvGNl1zpnrmhCUfZjrLInQ3gweUxRerM7Lo= MIME-Version: 1.0 Received: by 10.151.48.20 with SMTP id a20mr500486ybk.112.1246225877144; Sun, 28 Jun 2009 14:51:17 -0700 (PDT) In-Reply-To: References: Date: Sun, 28 Jun 2009 16:51:17 -0500 Message-ID: From: Alan Cox To: Wojciech Puchar Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-hackers@freebsd.org Subject: Re: large pages (amd64) X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: alc@freebsd.org List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 28 Jun 2009 22:16:03 -0000 On Sun, Jun 28, 2009 at 12:36 PM, Wojciech Puchar < wojtek@wojtek.tensor.gdynia.pl> wrote: > i enabled > vm.pmap.pg_ps_enabled: 1 > > > could you please explain what exactly this values means? > because i don't understand why promotions-demotions!=mappings > "mappings" is not what you seem to think it is. vm.pmap.pde.mappings is the number of 2/4MB page mappings that are created directly and not through the incremental promotion process. For example, it counts the 2/4MB page mappings that are created when the text segment of a large executable, e.g., gcc, is pre-faulted at startup or when a graphics card's frame buffer is mmap()ed. Moreover, not every promoted mapping is demoted. A promoted mapping may be destroyed without demotion, for example, when a process exits. This is, in fact, the ideal case because it is cheaper to destroy a single 2/4MB page mapping instead of 512 or 1024 4KB page mappings. > > vm.pmap.pde.promotions: 2703 > vm.pmap.pde.p_failures: 6290 > vm.pmap.pde.mappings: 610 > vm.pmap.pde.demotions: 289 > > > > > other question - tried enabling it on my i386 laptop (256 megs ram), always > mappings==0, while promitions>demotions>0. > The default starting address for executables on i386 is not aligned to a 2/4MB page boundary. Hence, "mappings" are much less likely to occur. > certainly there are apps that could be put on big pages, gimp editing 40MB > bitmap for example Regards, Alan