Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752299AbXBDLKN (ORCPT ); Sun, 4 Feb 2007 06:10:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752301AbXBDLKM (ORCPT ); Sun, 4 Feb 2007 06:10:12 -0500 Received: from nf-out-0910.google.com ([64.233.182.189]:30242 "EHLO nf-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752299AbXBDLKL (ORCPT ); Sun, 4 Feb 2007 06:10:11 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=gnYXkvwbhWDCGJ+Zwp8ZbxERHnCZfw18e2H4ZOTo4sISq4ki6jmacxmFjR7yaimnCXWUmlfvUA6vvv2H6F+AifTW7vJeFslrVjU8cHxPnjOcl3oO9oFRCfjHKM+qK1hRp8N/ISMafmQVJGAzUe/AlGWHDyELMugDd/NWas/ahDM= Message-ID: Date: Sun, 4 Feb 2007 16:40:09 +0530 From: "yogeshwar sonawane" To: davids@webmaster.com Subject: Re: Excessive printks increase top mem usage? Cc: linux-kernel In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline References: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2803 Lines: 67 cc to lkml On 2/3/07, yogeshwar sonawane wrote: > Thanks for the explanation. > > On 1/26/07, David Schwartz wrote: > > > > > On 1/25/07, yogeshwar sonawane wrote: > > > > Hi all, > > > > I am running a user application which will just open/close my driver > > > > (simple one, empty functions with only printks) infinitely. > > > > A massive use of printk can slow down the system noticeably OR it can > > > > affect some time calculations. > > > > Apart from this, it was increasing top mem usage also. After closing > > > > the application, the memory consumption was not coming down(not > > > > freeing mem). Is this the expected behaviour? OR i am missing > > > > something? > > > > > > > > Can anybody help me in guiding the reason for this? Any help/links plz. > > > > > > > > Thanks in advance, > > > > Yogeshwar > > > > What does "increased top mem usage" mean? You have given no reason to > > suggest that there's anything unusual about this. > > > > Here's one theory: Some program is writing these kernel messages to a file. > > Because some other process might come and read that file later, the kernel > > keeps copies of the file data in memory. > > > > The kernel sees no advantage in having memory free. Free memory is memory > > that's not doing any good. Better to keep data in memory that might be > > useful later. We can always free the memory later if (and only if) we have > > something better to do with it. > > One more thing:- > If i want to allocate physical memory using __get_free_pages, and > there is no free mem available, then kernel will release mem used by > file data & use it for my request. Is this correct? > I just tried similar thing. My test machine has 4GB RAM. On my test > machine, as explained in my previous mail, i was printing excessive > messages. Due to this top was showing mem usage aroung 1.9GB. Then i > tried allocation of 4MB phy mem(using __get_free_pages) iteratively > till it fails. The allocation succeeded upto @ 4-1.9 GB. I thought > that some mem from 1.9 GB will be released for phy mem allocation. But > it didn't. Such runs were tried 3-4 times. But consistently it > succeeded upto 4-1.9GB. So is this normal ? > > regards, > Yogeshwar > > > > > DS > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/