From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id B25D86B0069 for ; Wed, 22 Nov 2017 04:11:01 -0500 (EST) Received: by mail-pg0-f69.google.com with SMTP id p9so15664855pgc.6 for ; Wed, 22 Nov 2017 01:11:01 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id a14si12915047pgv.479.2017.11.22.01.11.00 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 22 Nov 2017 01:11:00 -0800 (PST) Date: Wed, 22 Nov 2017 10:10:56 +0100 From: Michal Hocko Subject: Re: [PATCH v2] mm: show total hugetlb memory consumption in /proc/meminfo Message-ID: <20171122091056.axzpd7tb3mxif4sg@dhcp22.suse.cz> References: <20171115231409.12131-1-guro@fb.com> <20171120165110.587918bf75ffecb8144da66c@linux-foundation.org> <20171121151545.GA23974@castle> <20171121111907.6952d50adcbe435b1b6b4576@linux-foundation.org> <20171121195947.GA12709@castle> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Mike Kravetz Cc: Roman Gushchin , Andrew Morton , linux-mm@kvack.org, Johannes Weiner , "Aneesh Kumar K.V" , Andrea Arcangeli , Dave Hansen , David Rientjes , kernel-team@fb.com, linux-kernel@vger.kernel.org On Tue 21-11-17 16:27:38, Mike Kravetz wrote: > On 11/21/2017 11:59 AM, Roman Gushchin wrote: [...] > > What we can do, is to rename "count" into "nr_huge_pages", like: > > > > for_each_hstate(h) { > > unsigned long nr_huge_pages = h->nr_huge_pages; > > > > total += (PAGE_SIZE << huge_page_order(h)) * nr_huge_pages; > > > > if (h == &default_hstate) > > seq_printf(m, > > "HugePages_Total: %5lu\n" > > "HugePages_Free: %5lu\n" > > "HugePages_Rsvd: %5lu\n" > > "HugePages_Surp: %5lu\n" > > "Hugepagesize: %8lu kB\n", > > nr_huge_pages, > > h->free_huge_pages, > > h->resv_huge_pages, > > h->surplus_huge_pages, > > (PAGE_SIZE << huge_page_order(h)) / 1024); > > } > > > > seq_printf(m, "Hugetlb: %8lu kB\n", total / 1024); > > > > But maybe taking a lock is not a bad idea, because it will also > > guarantee consistency between other numbers (like HugePages_Free) as well, > > which is not true right now. > > You are correct in that there is no consistency guarantee for the numbers > with the default huge page size today. However, I am not really a fan of > taking the lock for that guarantee. IMO, the above code is fine. I agree > This discussion reminds me that ideally there should be a per-hstate lock. > My guess is that the global lock is a carry over from the days when only > a single huge page size was supported. In practice, I don't think this is > much of an issue as people typically only use a single huge page size. But, > if anyone thinks is/may be an issue I am happy to make the changes. Well, it kind of makes sense but I am not sure it is worth bothering. -- Michal Hocko SUSE Labs -- 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