From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx131.postini.com [74.125.245.131]) by kanga.kvack.org (Postfix) with SMTP id 682F76B005C for ; Mon, 19 Dec 2011 15:45:43 -0500 (EST) Received: by yhgm50 with SMTP id m50so3076003yhg.14 for ; Mon, 19 Dec 2011 12:45:42 -0800 (PST) Message-ID: <4EEFA278.7010200@gmail.com> Date: Mon, 19 Dec 2011 15:45:44 -0500 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [RFC][PATCH 2/3] pagemap: export KPF_THP References: <1324319919-31720-1-git-send-email-n-horiguchi@ah.jp.nec.com> <1324319919-31720-3-git-send-email-n-horiguchi@ah.jp.nec.com> <4EEF8F85.9010408@gmail.com> <4EEF9F3E.9000107@linux.vnet.ibm.com> In-Reply-To: <4EEF9F3E.9000107@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dave Hansen Cc: Naoya Horiguchi , linux-mm@kvack.org, Andi Kleen , Wu Fengguang , Andrea Arcangeli , KOSAKI Motohiro , KAMEZAWA Hiroyuki , linux-kernel@vger.kernel.org (12/19/11 3:31 PM), Dave Hansen wrote: > On 12/19/2011 11:24 AM, KOSAKI Motohiro wrote: >> (12/19/11 1:38 PM), Naoya Horiguchi wrote: >>> This flag shows that a given pages is a subpage of transparent hugepage. >>> It does not care about whether it is a head page or a tail page, because >>> it's clear from pfn of the target page which you should know when you read >>> /proc/kpageflags. >>> >>> Signed-off-by: Naoya Horiguchi >> >> NAK. >> >> The detail of transparent hugepage are hidden by design. We hope it >> keep 'transparent'. >> Until any explain why we should expose KPF_THP, we don't agree it. > > Transparent shouldn't mean "undebuggable", though. :) > > Let's say you profiled a application and the data shows you're missing > the TLB a bunch, but you're also using THP. This might give you a shot > at figuring out which parts of your application are *TRULY* THP-backed > instead of just the areas you *think* are backed. > > I'm not sure there's another way to figure it out at the moment. A snapshot status of THP doesn't help your purpose. I think you need perf or similar profiling subsystem enhancement. Because of, if you've seen KPF_THP at once, It has no guarantee to keep hugepages until applications run. Opposite, If you only need rough statistics, the best way is to add some new stat to /sys/kernel/mm/transparent_hugepage. I don't think your usecase and current proposal are matched. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org