Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932284AbVJQMAL (ORCPT ); Mon, 17 Oct 2005 08:00:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932286AbVJQMAL (ORCPT ); Mon, 17 Oct 2005 08:00:11 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:39562 "EHLO e1.ny.us.ibm.com") by vger.kernel.org with ESMTP id S932284AbVJQMAJ (ORCPT ); Mon, 17 Oct 2005 08:00:09 -0400 Date: Mon, 17 Oct 2005 17:24:00 +0530 From: Dipankar Sarma To: Linus Torvalds Cc: Serge Belyshev , linux-kernel@vger.kernel.org, khali@linux-fr.org, Andrew Morton , Manfred Spraul Subject: Re: VFS: file-max limit 50044 reached Message-ID: <20051017115400.GC6257@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <87fyr2ape5.fsf@foo.vault.bofh.ru> <87slv23bw5.fsf@foo.vault.bofh.ru> <20051016162306.GA10410@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.10i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1485 Lines: 36 On Sun, Oct 16, 2005 at 07:34:24PM -0700, Linus Torvalds wrote: > On Sun, 16 Oct 2005, Dipankar Sarma wrote: > > > > Linus, I don't think this has anything to do with RCU grace periods > > like we discussed previously. I measured on my 3.6GHz x86_64 and > > found that open()/close() pair on /dev/null takes about 45500 > > cycles or 12 microseconds. [Does that sound resonable?]. > > That sounds very slow. I can do a million open/close pairs in 4 seconds on > a 2.5GHz G5. Maybe you tested a cold-cache case? I measured after warming up for about a 100 times or so. It is not a cold-cache case. I think we have a bigger problem in hand here. I measured this with 2.6.13 and saw that I could do the same in ~3 microseconds per iteration. It balloons to 12 microseconds in 2.6.14-rc1. I am looking at this right now apart from the other problems. > I suspect this patch is worth it for the 2.6.14 timeframe, but I'll wait > for confirmation. > > In fact, for 2.6.14, I'd almost do an even more minimal one. I agree with > your changing the file counter to an atomic, but I'd rather keep that > change for later. Even beyond the file counter issue, we do need to address the DoS and the open/close slowdown issue. Thanks Dipankar - 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/