From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f176.google.com (mail-wi0-f176.google.com [209.85.212.176]) by kanga.kvack.org (Postfix) with ESMTP id 1EB096B0258 for ; Thu, 10 Sep 2015 13:02:59 -0400 (EDT) Received: by wiclk2 with SMTP id lk2so35997621wic.0 for ; Thu, 10 Sep 2015 10:02:58 -0700 (PDT) Received: from mail.anarazel.de (mail.anarazel.de. [217.115.131.40]) by mx.google.com with ESMTP id p10si12684428wik.84.2015.09.10.10.02.57 for ; Thu, 10 Sep 2015 10:02:57 -0700 (PDT) Date: Thu, 10 Sep 2015 19:02:53 +0200 From: Andres Freund Subject: Re: Can we disable transparent hugepages for lack of a legitimate use case please? Message-ID: <20150910170253.GA6197@alap3.anarazel.de> References: <20150824201952.5931089.66204.70511@amd.com> <20150910164506.GK10639@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150910164506.GK10639@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: James Hartshorn , "Bridgman, John" , "linux-mm@kvack.org" On 2015-09-10 18:45:06 +0200, Andrea Arcangeli wrote: > On Mon, Aug 24, 2015 at 08:46:11PM +0000, James Hartshorn wrote: > > Some more links to discussion > > about THP: Postgresql https://lwn.net/Articles/591723/ Postgresql > > http://www.postgresql.org/message-id/20120821131254.1415a545@jekyl.davidgould.org > > "and my interpretation was that it was trying to create hugepages from > scattered fragments" > > This is a very old email, but I'm just taking it as an example because > this has to be a compaction issue. If you run into very visible hangs > that goes away by disabling THP, it can't be THP to blame. THP can > increase the latency jitter during page faults (real time sensitive > application could notice a 2MB clear_page vs a 4KB clear_page), but > not in a way that hangs a system and becomes visible to the user. > > It's just very early compaction code was too aggressive and it got > fixed in the meanwhile. There's still some slowdown (as of 4.0) in extreme postgres workloads with THP and/or compaction enabled, but I've indeed not been able to reproduce bad stalls or large (10%+) slowdowns with recent kernels. Greetings, Andres Freund -- 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