From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 22116 invoked by alias); 6 Nov 2006 20:55:57 -0000 Received: (qmail 22109 invoked by uid 22791); 6 Nov 2006 20:55:56 -0000 X-Spam-Status: No, hits=-1.7 required=5.0 tests=AWL,BAYES_05,SPF_HELO_PASS,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mx1.redhat.com (HELO mx1.redhat.com) (66.187.233.31) by sourceware.org (qpsmtpd/0.31) with ESMTP; Mon, 06 Nov 2006 20:55:51 +0000 Received: from int-mx1.corp.redhat.com (int-mx1.corp.redhat.com [172.16.52.254]) by mx1.redhat.com (8.12.11.20060308/8.12.11) with ESMTP id kA6Ktnqc019502 for ; Mon, 6 Nov 2006 15:55:49 -0500 Received: from pobox.toronto.redhat.com (pobox.toronto.redhat.com [172.16.14.4]) by int-mx1.corp.redhat.com (8.13.1/8.13.1) with ESMTP id kA6KtiSg032522; Mon, 6 Nov 2006 15:55:44 -0500 Received: from touchme.toronto.redhat.com (IDENT:postfix@touchme.toronto.redhat.com [172.16.14.9]) by pobox.toronto.redhat.com (8.12.11.20060308/8.12.11) with ESMTP id kA6Kti0E006533; Mon, 6 Nov 2006 15:55:44 -0500 Received: from ton.toronto.redhat.com (ton.toronto.redhat.com [172.16.14.15]) by touchme.toronto.redhat.com (Postfix) with ESMTP id 3E3C5800002; Mon, 6 Nov 2006 15:55:44 -0500 (EST) Received: from ton.toronto.redhat.com (localhost.localdomain [127.0.0.1]) by ton.toronto.redhat.com (8.13.1/8.13.1) with ESMTP id kA6KthXK018434; Mon, 6 Nov 2006 15:55:43 -0500 Received: (from fche@localhost) by ton.toronto.redhat.com (8.13.1/8.13.1/Submit) id kA6KthW0018431; Mon, 6 Nov 2006 15:55:43 -0500 X-Authentication-Warning: ton.toronto.redhat.com: fche set sender to fche@redhat.com using -f To: Martin Hunt Cc: systemtap@sources.redhat.com Subject: Re: offline elfutils processing committed References: <20061101021300.GV4978@redhat.com> <20061101200336.7B0A8180053@magilla.sf.frob.com> <20061103234334.GC29330@redhat.com> <1162839113.2797.33.camel@dragon> From: fche@redhat.com (Frank Ch. Eigler) Date: Mon, 06 Nov 2006 21:18:00 -0000 In-Reply-To: <1162839113.2797.33.camel@dragon> Message-ID: User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2006-q4/txt/msg00352.txt.bz2 Martin Hunt writes: > [...] > > It however exposes two problems with the newest symbol table code. > > First, the new _stp_module_lookup function holds a spinlock on its > > data structure, which could conceivably block. > > Is there some reason why the $target variable must be looked up each > time it is accessed? Sounds slow. It was the simplest functional expedient. > I put the spinlock in at the last minute because I was worried that > someone might be tempted to use it to try to resolve addresses > during a kprobe. [...] What would be the harm in that? IOW, what kind of concurrency problem is the lock intended to prevent? > [...] Moving the allocations into .data or .bss sections could > still trigger OOM situations. Yes, however, the difference is that even if the allocation size were configurable by a user, it would be expressed in obvious units (megabytes, rather than array rows). > [...] I made this argument a year ago and was told to rewrite to > allocate memory in small chunks with kmalloc. [...] You will recall that, at the time, we were experiencing problems with probing the proximity of the vmalloc fault handler path. > Regarding OOM killer, shouldn't we just set oom_adj to something > like +15? That would put us at the top of the victims list [...] Who is that "us"? The staprun process? It's too late by then - the module will not notice that staprun is gone until after the module's allocation attempts have hurt the system. - FChE