From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: Re: [PATCH 17/18] fs: icache remove inode_lock Date: Sat, 16 Oct 2010 00:29:38 +1100 Message-ID: <20101015132938.GA3936@amd> References: <20101013232319.GZ4681@dastard> <20101014090609.GB3144@amd> <20101014144159.GA11972@infradead.org> <20101015001443.GA3146@amd> <20101015031343.GG4681@dastard> <20101015033017.GA6750@amd> <20101015034451.GA6827@amd> <20101015064150.GB7511@amd> <20101015105943.GE32255@dastard> <20101015130259.GA3207@amd> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Dave Chinner , Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Nick Piggin Return-path: Received: from ipmail04.adl6.internode.on.net ([150.101.137.141]:45999 "EHLO ipmail04.adl6.internode.on.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754545Ab0JON3n (ORCPT ); Fri, 15 Oct 2010 09:29:43 -0400 Content-Disposition: inline In-Reply-To: <20101015130259.GA3207@amd> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Sat, Oct 16, 2010 at 12:03:00AM +1100, Nick Piggin wrote: > On Fri, Oct 15, 2010 at 09:59:43PM +1100, Dave Chinner wrote: > > My series uses i_lock only to protect i_state and i_ref. It does not > > need to protect any more of the inode than that as other locks > > protect the other list fields. As a result, it's still the inermost > > lock and there are no trylocks in the code at all. > We discussed it and I didn't think latencies would be any worse > a problem than they are today. I agreed it may be an issue and > pointed out there are ways forward to fix it. BTW. if a few trylocks are your biggest issue, this is a joke. I told you how they can be fixed with incremental patches on top of the series (which basically whittle down the lock coverage of the old inode_lock, and so IMO need to be done in small chunks well bisectable and with good rationale). So why you didn't submit a couple of incremental patches to do just that is beyond me. I've had prototypes in my tree actually to do that from a while back, but actually I'm thinking that using RCU may be a better way to go now that Linus has agreed on it and we have sketched a design to do slab-free-RCU. Either way, it's much easier to compare pros and cons of each, when they are done incrementally on top of the existing base.