From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 7D79D6B032E for ; Tue, 6 Nov 2018 09:06:41 -0500 (EST) Received: by mail-ed1-f69.google.com with SMTP id m45-v6so7743791edc.2 for ; Tue, 06 Nov 2018 06:06:41 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id e19si3289019edv.104.2018.11.06.06.06.39 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Nov 2018 06:06:39 -0800 (PST) Date: Tue, 6 Nov 2018 15:06:38 +0100 From: Michal Hocko Subject: Re: [PATCH v6 1/2] memory_hotplug: Free pages as higher order Message-ID: <20181106140638.GN27423@dhcp22.suse.cz> References: <1541484194-1493-1-git-send-email-arunks@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1541484194-1493-1-git-send-email-arunks@codeaurora.org> Sender: owner-linux-mm@kvack.org List-ID: To: Arun KS Cc: arunks.linux@gmail.com, akpm@linux-foundation.org, vbabka@suse.cz, osalvador@suse.de, linux-kernel@vger.kernel.org, linux-mm@kvack.org, getarunks@gmail.com On Tue 06-11-18 11:33:13, Arun KS wrote: > When free pages are done with higher order, time spend on > coalescing pages by buddy allocator can be reduced. With > section size of 256MB, hot add latency of a single section > shows improvement from 50-60 ms to less than 1 ms, hence > improving the hot add latency by 60%. Modify external > providers of online callback to align with the change. > > This patch modifies totalram_pages, zone->managed_pages and > totalhigh_pages outside managed_page_count_lock. A follow up > series will be send to convert these variable to atomic to > avoid readers potentially seeing a store tear. Is there any reason to rush this through rather than wait for counters conversion first? The patch as is looks good to me - modulo atomic counters of course. I cannot really judge whether existing updaters do really race in practice to take this riskless. The improvement is nice of course but this is a rare operation and 50ms vs 1ms is hardly noticeable. So I would rather wait for the preparatory work to settle. Btw. is there anything blocking that? It seems to be mostly automated. -- Michal Hocko SUSE Labs