Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753120Ab0KGXAc (ORCPT ); Sun, 7 Nov 2010 18:00:32 -0500 Received: from x35.xmailserver.org ([64.71.152.41]:35714 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751369Ab0KGXAb (ORCPT ); Sun, 7 Nov 2010 18:00:31 -0500 X-AuthUser: davidel@xmailserver.org Date: Sun, 7 Nov 2010 14:59:27 -0800 (PST) From: Davide Libenzi X-X-Sender: davide@davide-lnx1 To: Matt Helsley cc: Tejun Heo , Oren Laadan , ksummit-2010-discuss@lists.linux-foundation.org, Linux Kernel Mailing List Subject: Re: [Ksummit-2010-discuss] checkpoint-restart: naked patch In-Reply-To: <20101106101209.GD11535@count0.beaverton.ibm.com> Message-ID: References: <4CD08419.5050803@kernel.org> <4CD23087.30900@cs.columbia.edu> <4CD28033.1000700@kernel.org> <20101106101209.GD11535@count0.beaverton.ibm.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2543 Lines: 57 On Sat, 6 Nov 2010, Matt Helsley wrote: > Yes, our patches touch a wide variety of kernel code. You have just failed > to appreciate how "wide" the kernel ABI truly is. You can't really count > it by number of syscalls, number of pseudo-filesystems, etc. There's > also the intended behavior of those interfaces to consider. Each piece > of checkpoint/restart code is relatively self-contained. This can be > confirmed merely by looking at many of the patches we've already posted > enabling checkpoint/restart of that feature. Until you've tried to > implement checkpoint/restart for an interface or until you've bothered > to review a patch for one of them (my favorite on is eventfd: > http://www.mail-archive.com/devel@openvz.org/msg21565.html ) please > don't tell us it's too complex. Then compare that with your proposed > ghastly stack of userspace cards -- ptrace (really more like strace) + > LD_PRELOAD + a daemon... > > Incidentally, 20k lines of code is less than many pieces of the kernel. > It's less than many: > > Filesystems (I've selected ones designed for rotating media or networks usually..) > ext4, nfs, ocfs2, xfs, reiserfs, ntfs, gfs2, jfs, cifs, ubifs, nilfs2, btrfs > > Non-filesystem file-system support code: > nfsd, nls > > It's less than one of the simpler DRM graphics drivers -- i915: > $ cd drivers/gpu/drm/i915 > $ wc -l *.[ch] > ... > 41481 total > > It's less than any one of the lpfc, bfa, aic7xxx, qla2xxx, and mpt2sas > drivers I see under scsi. Perhaps a more fair comparison might be to compare > a single driver to a single checkpointable kernel interface but it's > a more-fair comparison that skews even more in our favor. Please, do not compare things like single file systems, drivers, or otherwise fairly isolated components, with this "thing". This thing touches a freaky-large number of subsystems, effectively adding a glueage between them, which can might end up causing problems (and/or restrict design choices) in the future. The naked patch looks like just a sugar coating to me, which left out 300+ lines of extra logic in epoll alone. This is one of the widest, deepest, intrusive patches I have seen in a while, whose inclusion would require a little bit more than handwaving and continuous re-posting IMO. - Davide -- 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/