From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 71E94280264 for ; Thu, 22 Dec 2016 14:28:40 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id f188so662529680pgc.1 for ; Thu, 22 Dec 2016 11:28:40 -0800 (PST) Received: from mail-pg0-x236.google.com (mail-pg0-x236.google.com. [2607:f8b0:400e:c05::236]) by mx.google.com with ESMTPS id r79si8611594pfl.8.2016.12.22.11.28.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 22 Dec 2016 11:28:39 -0800 (PST) Received: by mail-pg0-x236.google.com with SMTP id y62so48718725pgy.1 for ; Thu, 22 Dec 2016 11:28:39 -0800 (PST) Date: Thu, 22 Dec 2016 11:28:31 -0800 (PST) From: Hugh Dickins Subject: Re: [RFC][PATCH] make global bitlock waitqueues per-node In-Reply-To: Message-ID: References: <20161219225826.F8CB356F@viggo.jf.intel.com> <156a5b34-ad3b-d0aa-83c9-109b366c1bdf@linux.intel.com> <20161221080931.GQ3124@twins.programming.kicks-ass.net> <20161221083247.GW3174@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Peter Zijlstra , Nick Piggin , Dave Hansen , Bob Peterson , Linux Kernel Mailing List , Steven Whitehouse , Andrew Lutomirski , Andreas Gruenbacher , Mel Gorman , linux-mm On Wed, 21 Dec 2016, Linus Torvalds wrote: > On Wed, Dec 21, 2016 at 12:32 AM, Peter Zijlstra wrote: > > > > FWIW, here's mine.. compiles and boots on a NUMA x86_64 machine. > > So I like how your patch is smaller, but your patch is also broken. > > First off, the whole contention bit is *not* NUMA-specific. It should > help non-NUMA too, by avoiding the stupid extra cache miss. > > Secondly, CONFIG_NUMA is a broken thing to test anyway, since adding a > bit for the NUMA case can overflow the page flags as far as I can tell > (MIPS seems to support NUMA on 32-bit, for example, but I didn't > really check the Kconfig details). Making it dependent on 64-bit might > be ok (and would fix the issue above - I don't think we really need to > care too much about 32-bit any more) > > But making it conditional at all means that now you have those two > different cases for this, which is a maintenance nightmare. So don't > do it even if we could say "screw 32-bit". > > Anyway, the conditional thing could be fixed by just taking Nick's > patch 1/2, and your patch (with the conditional bits stripped out). Yup. > > I do think your approach of just re-using the existing bit waiting > with just a page-specific waiting function is nicer than Nick's "let's > just roll new waiting functions" approach. It also avoids the extra > initcall. > > Nick, comments? > > Hugh - mind testing PeterZ's patch too? My comments about the > conditional PG_waiters bit and page bit overflow are not relevant for > your particular scenario, so you can ignore that part, and just take > PaterZ's patch directly. Right, I put them both through some loads yesterday and overnight: Peter's patch and Nick's patch each work fine here, no issues seen with either (but I didn't attempt to compare them, aesthetically nor in performance). Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org