From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f178.google.com (mail-ie0-f178.google.com [209.85.223.178]) by kanga.kvack.org (Postfix) with ESMTP id 772306B0038 for ; Mon, 2 Mar 2015 21:37:48 -0500 (EST) Received: by iecrp18 with SMTP id rp18so53564062iec.1 for ; Mon, 02 Mar 2015 18:37:48 -0800 (PST) Received: from mail-ig0-x22f.google.com (mail-ig0-x22f.google.com. [2607:f8b0:4001:c05::22f]) by mx.google.com with ESMTPS id h130si226007ioh.98.2015.03.02.18.37.48 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 02 Mar 2015 18:37:48 -0800 (PST) Received: by igal13 with SMTP id l13so22982423iga.5 for ; Mon, 02 Mar 2015 18:37:48 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <20150302010413.GP4251@dastard> <20150303014733.GL18360@dastard> Date: Mon, 2 Mar 2015 18:37:47 -0800 Message-ID: Subject: Re: [regression v4.0-rc1] mm: IPIs from TLB flushes causing significant performance degradation. From: Linus Torvalds Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Dave Chinner , Mel Gorman Cc: Andrew Morton , Ingo Molnar , Matt B , Linux Kernel Mailing List , linux-mm , xfs@oss.sgi.com On Mon, Mar 2, 2015 at 6:22 PM, Linus Torvalds wrote: > > There might be some other case where the new "just change the > protection" doesn't do the "oh, but it the protection didn't change, > don't bother flushing". I don't see it. Hmm. I wonder.. In change_pte_range(), we just unconditionally change the protection bits. But the old numa code used to do if (!pte_numa(oldpte)) { ptep_set_numa(mm, addr, pte); so it would actually avoid the pte update if a numa-prot page was marked numa-prot again. But are those migrate-page calls really common enough to make these things happen often enough on the same pages for this all to matter? Odd. So it would be good if your profiles just show "there's suddenly a *lot* more calls to flush_tlb_page() from XYZ" and the culprit is obvious that way.. Linus -- 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