From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD8FDC0044C for ; Mon, 5 Nov 2018 14:27:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8158F20819 for ; Mon, 5 Nov 2018 14:27:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8158F20819 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729532AbeKEXrg (ORCPT ); Mon, 5 Nov 2018 18:47:36 -0500 Received: from mga07.intel.com ([134.134.136.100]:2490 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726173AbeKEXrg (ORCPT ); Mon, 5 Nov 2018 18:47:36 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Nov 2018 06:27:29 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,468,1534834800"; d="scan'208";a="86795185" Received: from aaronlu.sh.intel.com (HELO intel.com) ([10.239.159.44]) by orsmga007.jf.intel.com with ESMTP; 05 Nov 2018 06:27:27 -0800 Date: Mon, 5 Nov 2018 22:27:27 +0800 From: Aaron Lu To: Michal Hocko Cc: Vasily Averin , linux-mm@kvack.org, Andrew Morton , Huang Ying , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm: use kvzalloc for swap_info_struct allocation Message-ID: <20181105142727.GB6203@intel.com> References: <20181105061016.GA4502@intel.com> <20181105141156.GB10132@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181105141156.GB10132@dhcp22.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 05, 2018 at 03:11:56PM +0100, Michal Hocko wrote: > On Mon 05-11-18 14:17:01, Vasily Averin wrote: > > commit a2468cc9bfdf ("swap: choose swap device according to numa node") > > changed 'avail_lists' field of 'struct swap_info_struct' to an array. > > In popular linux distros it increased size of swap_info_struct up to > > 40 Kbytes and now swap_info_struct allocation requires order-4 page. > > Switch to kvzmalloc allows to avoid unexpected allocation failures. > > While this fixes the most visible issue is this a good long term > solution? Aren't we wasting memory without a good reason? IIRC our limit That's right, we need a better way of handling this in the long term. > for swap files/devices is much smaller than potential NUMA nodes numbers > so we can safely expect that would be only few numa affine nodes. I am > not really familiar with the rework which has added numa node awareness > but I wouls assueme that we should either go with one global table with > a linked list of possible swap_info structure per numa node or use a > sparse array. There is a per-numa-node plist of available swap devices, so every swap device needs an entry on those per-numa-node plist. I think we can convert avail_lists from array to pointer and use vzalloc to allocate the needed memory. MAX_NUMANODES can be used for a simple implementation, or use the precise online node number but then we will need to handle node online/offline events. sparse array sounds promising, I'll take a look, thanks for the pointer. > That being said I am not really objecting to this patch as it is simple > and backportable to older (stable kernels). > > I would even dare to add > Fixes: a2468cc9bfdf ("swap: choose swap device according to numa node") > > because not being able to add a swap space on a fragmented system looks > like a regression to me. Agree, especially it used to work. Regards, Aaron > > Acked-by: Aaron Lu > > Signed-off-by: Vasily Averin > > Acked-by: Michal Hocko > > --- > > mm/swapfile.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > index 644f746e167a..8688ae65ef58 100644 > > --- a/mm/swapfile.c > > +++ b/mm/swapfile.c > > @@ -2813,7 +2813,7 @@ static struct swap_info_struct *alloc_swap_info(void) > > unsigned int type; > > int i; > > > > - p = kzalloc(sizeof(*p), GFP_KERNEL); > > + p = kvzalloc(sizeof(*p), GFP_KERNEL); > > if (!p) > > return ERR_PTR(-ENOMEM); > > > > @@ -2824,7 +2824,7 @@ static struct swap_info_struct *alloc_swap_info(void) > > } > > if (type >= MAX_SWAPFILES) { > > spin_unlock(&swap_lock); > > - kfree(p); > > + kvfree(p); > > return ERR_PTR(-EPERM); > > } > > if (type >= nr_swapfiles) { > > @@ -2838,7 +2838,7 @@ static struct swap_info_struct *alloc_swap_info(void) > > smp_wmb(); > > nr_swapfiles++; > > } else { > > - kfree(p); > > + kvfree(p); > > p = swap_info[type]; > > /* > > * Do not memset this entry: a racing procfs swap_next() > > -- > > 2.17.1 > > -- > Michal Hocko > SUSE Labs >