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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 D6F1DCA9EA0 for ; Tue, 22 Oct 2019 08:30:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DB6621872 for ; Tue, 22 Oct 2019 08:30:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571733013; bh=43hrKQLS/Gs7waQl0DuVQvlooxJE8xr0Ca6LsXfDUJk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=mPJw0AefaLakbGavjOCWO/O7gttLQlxbCDKHYHrZUa/5nP/AaMGfQYai8LBFnwOQh gldetYaPdqKtQFyd+GdZP3igWrqQ0jkhAvSdadbzO9Fr0MIA/9tBPg4HFq1EPQjvcb Bhws6gq2xTOgeguhbqEsijY7cdAEd2zxJY9l+IWk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388395AbfJVIaM (ORCPT ); Tue, 22 Oct 2019 04:30:12 -0400 Received: from mx2.suse.de ([195.135.220.15]:40284 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388061AbfJVIaL (ORCPT ); Tue, 22 Oct 2019 04:30:11 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 79712ACA0; Tue, 22 Oct 2019 08:30:02 +0000 (UTC) Date: Tue, 22 Oct 2019 10:30:02 +0200 From: Michal Hocko To: Oscar Salvador Cc: n-horiguchi@ah.jp.nec.com, mike.kravetz@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 11/16] mm,hwpoison: Rework soft offline for in-use pages Message-ID: <20191022083002.GE9379@dhcp22.suse.cz> References: <20191017142123.24245-1-osalvador@suse.de> <20191017142123.24245-12-osalvador@suse.de> <20191018123901.GN5017@dhcp22.suse.cz> <20191021134846.GB11330@linux> <20191021140619.GQ9379@dhcp22.suse.cz> <20191022075626.GB19060@linux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191022075626.GB19060@linux> 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 Tue 22-10-19 09:56:27, Oscar Salvador wrote: > On Mon, Oct 21, 2019 at 04:06:19PM +0200, Michal Hocko wrote: > > On Mon 21-10-19 15:48:48, Oscar Salvador wrote: > > > We can only perform actions on LRU/Movable pages or hugetlb pages. > > > > What would prevent other pages mapped via page tables to be handled as > > well? > > What kind of pages? Any pages mapped to the userspace. E.g. driver memory which is not on LRU. > I mean, I guess it could be done, it was just not implemented, and I > did not want to add more "features" as my main goal was to re-work > the interface to be more deterministic. Fair enough. One step at the time sounds definitely good > > > 1) we would need to hook in enqueue_hugetlb_page so the page is not enqueued > > > into hugetlb freelists > > > 2) when trying to free a hugetlb page, we would need to do as we do for gigantic > > > pages now, and that is breaking down the pages into order-0 pages and release > > > them to the buddy (so the check in free_papges_prepare would skip the > > > hwpoison page). > > > Trying to handle a higher-order hwpoison page in free_pages_prepare is > > > a bit complicated. > > > > I am not sure I see the problem. If you dissolve the hugetlb page then > > there is no hugetlb page anymore and so you make it a regular high-order > > page. > > Yes, but the problem comes when trying to work with a hwpoison high-order page > in free_pages_prepare, it gets more complicated, and when I weigthed > code vs benefits, I was not really sure to go down that road. > > If we get a hwpoison high-order page in free_pages_prepare, we need to > break it down to smaller pages, so we can skip the "bad" to not be sent > into buddy allocator. But we have destructors for compound pages. Can we do the heavy lifting there? > > If the page is free then it shouldn't pin the memcg or any other state. > > Well, it is not really free, as it is not usable, is it? Sorry I meant to say the page is free from the memcg POV - aka no task from the memcg is holding a reference to it. The page is not usable for anybody, that is true but no particular memcg should pay a price for that. This would mean that random memcgs would end up pinned for ever without a good reason. -- Michal Hocko SUSE Labs