Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757388AbZF3XKj (ORCPT ); Tue, 30 Jun 2009 19:10:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753300AbZF3XKc (ORCPT ); Tue, 30 Jun 2009 19:10:32 -0400 Received: from mx2.redhat.com ([66.187.237.31]:48159 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753187AbZF3XKc (ORCPT ); Tue, 30 Jun 2009 19:10:32 -0400 Message-ID: <4A4A9BF1.4090703@redhat.com> Date: Tue, 30 Jun 2009 19:12:49 -0400 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Ingo Molnar CC: Ananth N Mavinakayanahalli , lkml , systemtap , DLE , Jim Keniston Subject: Re: [PATCH -tip 3/3] kprobes: cleanup: use list instead of hlist for insn_pages References: <20090630210757.17851.409.stgit@localhost.localdomain> <20090630210814.17851.64651.stgit@localhost.localdomain> <20090630212512.GA10831@elte.hu> <4A4A8804.1040004@redhat.com> <20090630215023.GA22851@elte.hu> In-Reply-To: <20090630215023.GA22851@elte.hu> X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1957 Lines: 64 Ingo Molnar wrote: > * Masami Hiramatsu wrote: > >> Ingo Molnar wrote: >>> * Masami Hiramatsu wrote: >>> >>>> Use struct list instead of struct hlist for managing insn_pages, >>>> because insn_pages doesn't use hash table. >>>> struct kprobe_insn_page { >>>> - struct hlist_node hlist; >>>> + struct list_head list; >>> Hm, you know that this increases the size of kprobe_insn_page by 4/8 >>> bytes, right? >> Sure, that will increase size. >> >>> hlists are not just used for hashes - but also when we want a more >>> compact / smaller list head. >> Oh, I thought hlists are used for hash tables... > > ... because they are smaller, hence the hash table of list > heads becomes twice as dense as with list_head. > > But otherwise it's an (almost) equivalent primitive to list_head, > with a slightly higher runtime cost versus better RAM footprint. > >>> How many kprobe_insn_page's can be allocated in the system, >>> maximally? >> It's depends on how many probes you will use, but logically, 1 >> kprobe_insn_pages is allocated per 4096/16 = 256 probes. So, if >> you use 25,600 probes on your system, memory consumption will >> increase 400/800 bytes. > > it's your call really - just wanted to react on the 'because it > should be used for hash tables' comment in the changelog. Hi Ingo, Would I might be misunderstood? struct list_head { struct list_head *next, *prev; }; struct hlist_node { struct hlist_node *next, **pprev; }; Both of list_head and hlist_node are the same size... -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division e-mail: mhiramat@redhat.com -- 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/