From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) by kanga.kvack.org (Postfix) with ESMTP id 254D46B033A for ; Tue, 6 Nov 2018 10:31:32 -0500 (EST) Received: by mail-pf1-f197.google.com with SMTP id n9-v6so12720342pfg.12 for ; Tue, 06 Nov 2018 07:31:32 -0800 (PST) Received: from smtp.codeaurora.org (smtp.codeaurora.org. [198.145.29.96]) by mx.google.com with ESMTPS id d12-v6si47339531pga.81.2018.11.06.07.31.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 06 Nov 2018 07:31:30 -0800 (PST) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 06 Nov 2018 21:01:29 +0530 From: Arun KS Subject: Re: [PATCH v6 1/2] memory_hotplug: Free pages as higher order In-Reply-To: <20181106140638.GN27423@dhcp22.suse.cz> References: <1541484194-1493-1-git-send-email-arunks@codeaurora.org> <20181106140638.GN27423@dhcp22.suse.cz> Message-ID: <542cd3516b54d88d1bffede02c6045b8@codeaurora.org> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko 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 2018-11-06 19:36, Michal Hocko wrote: > 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? Sure Michal. Conversion patch, https://patchwork.kernel.org/cover/10657217/ is currently incremental to this patch. I ll change the order. Will wait for preparatory patch to settle first. Regards, Arun. > > 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.