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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 CA038C433DB for ; Mon, 4 Jan 2021 19:30:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6F2EF207BC for ; Mon, 4 Jan 2021 19:30:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726019AbhADTat (ORCPT ); Mon, 4 Jan 2021 14:30:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725889AbhADTat (ORCPT ); Mon, 4 Jan 2021 14:30:49 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1A736C061574 for ; Mon, 4 Jan 2021 11:30:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=zMXccjfJXXeI6J1+siSWp8Bb0qMGr1Kxn66MZNWNsTw=; b=augF5D93uBWLlS3NI9UgDss8h9 kqmWUV9D9XMholR3eIMvCZrMLOuMxxXRzW4NjSpzyzBmdEORkHCbAeKpMOzQkigj/FfwalvxKcn53 Eq8aOSU5LAWBi6p8+bv1FsL2D31WYPgEtlgjFLGs31HAg9AaVq1i3HzguvYhYAB7DftESl7G1/MjW JRwT9EOwIKw6xCaTOmFhDuha2A39Tcg3KROlIKi7AfzbR+qrFsWoVSmuBsk2UIDBdwgsup8n6+lnQ FIA0QwrDv+Y2FDPq+iFIqvvPoCc94IhUeJHyU+cwrKfoEIJwmBavUcm42KMYVV8/rWQch26vuqctf PbYfT7Pg==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1kwVWD-000T52-Vz; Mon, 04 Jan 2021 19:28:03 +0000 Date: Mon, 4 Jan 2021 19:27:53 +0000 From: Matthew Wilcox To: Dave Hansen Cc: Alexander Duyck , Mel Gorman , Andrew Morton , Andrea Arcangeli , Dan Williams , "Michael S. Tsirkin" , David Hildenbrand , Jason Wang , Michal Hocko , Liang Li , linux-mm@kvack.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [RFC v2 PATCH 4/4] mm: pre zero out free pages to speed up page allocation for __GFP_ZERO Message-ID: <20210104192753.GD22407@casper.infradead.org> References: <20201221163024.GA22532@open-light-1.localdomain> <0e8b6a2f-527d-7c77-efcf-04f21ef2a77c@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0e8b6a2f-527d-7c77-efcf-04f21ef2a77c@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 04, 2021 at 11:19:13AM -0800, Dave Hansen wrote: > On 12/21/20 8:30 AM, Liang Li wrote: > > --- a/include/linux/page-flags.h > > +++ b/include/linux/page-flags.h > > @@ -137,6 +137,9 @@ enum pageflags { > > #endif > > #ifdef CONFIG_64BIT > > PG_arch_2, > > +#endif > > +#ifdef CONFIG_PREZERO_PAGE > > + PG_zero, > > #endif > > __NR_PAGEFLAGS, > > I don't think this is worth a generic page->flags bit. > > There's a ton of space in 'struct page' for pages that are in the > allocator. Can't we use some of that space? I was going to object to that too, but I think the entire approach is flawed and needs to be thrown out. It just nukes the caches in extremely subtle and hard to measure ways, lowering overall system performance.