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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 46F7DC3F2C6 for ; Wed, 4 Mar 2020 00:59:04 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id ECEEF20728 for ; Wed, 4 Mar 2020 00:59:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="cIEzDdbb" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org ECEEF20728 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 783E86B0003; Tue, 3 Mar 2020 19:59:03 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 734946B0005; Tue, 3 Mar 2020 19:59:03 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 64A0A6B0006; Tue, 3 Mar 2020 19:59:03 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0022.hostedemail.com [216.40.44.22]) by kanga.kvack.org (Postfix) with ESMTP id 4BAE46B0003 for ; Tue, 3 Mar 2020 19:59:03 -0500 (EST) Received: from smtpin30.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 0BDCF3A9E for ; Wed, 4 Mar 2020 00:59:03 +0000 (UTC) X-FDA: 76555870566.30.fang22_4efbb02643731 X-HE-Tag: fang22_4efbb02643731 X-Filterd-Recvd-Size: 4088 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Wed, 4 Mar 2020 00:59:02 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A1BD420728; Wed, 4 Mar 2020 00:58:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1583283540; bh=pBkv+zMpJnUHutM5TIKA7m+caWpqu0XAtFt3DpoXfP4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=cIEzDdbbbEFjL4w0k0SH481f3kjJzoI3WEPvR42mCswUUfFd22+Q3oxT2d7i4u2YK mHchKcRaDuxTpV1oOGOBRAy5BKCrCuh4tF3L34FLQCUdwYV4k9MmoGZuJ+m0HbZ1IF DaewpvraIeBODt7TnfBWu/LovTJHb/g8NCkSLNxo= Date: Tue, 3 Mar 2020 16:58:59 -0800 From: Andrew Morton To: "Huang, Ying" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dave Hansen , David Hildenbrand , Mel Gorman , Vlastimil Babka , Zi Yan , Michal Hocko , Peter Zijlstra , Minchan Kim , Johannes Weiner , Hugh Dickins Subject: Re: [PATCH] mm: Add PageLayzyFree() helper functions for MADV_FREE Message-Id: <20200303165859.7440f23d388503ca77fdb6c2@linux-foundation.org> In-Reply-To: <20200303033738.281908-1-ying.huang@intel.com> References: <20200303033738.281908-1-ying.huang@intel.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 3 Mar 2020 11:37:38 +0800 "Huang, Ying" wrote: > From: Huang Ying > > Now PageSwapBacked() is used as the helper function to check whether > pages have been freed lazily via MADV_FREE. This isn't very obvious. > So Dave suggested to add PageLazyFree() family helper functions to > improve the code readability. > > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -498,6 +498,31 @@ static __always_inline int PageKsm(struct page *page) > TESTPAGEFLAG_FALSE(Ksm) > #endif > > +/* > + * For pages freed lazily via MADV_FREE. lazyfree pages are clean > + * anonymous pages. They have SwapBacked flag cleared to distinguish > + * with normal anonymous pages > + */ > +static __always_inline int PageLazyFree(struct page *page) > +{ > + page = compound_head(page); > + return PageAnon(page) && !PageSwapBacked(page); > +} > + > +static __always_inline void SetPageLazyFree(struct page *page) > +{ > + VM_BUG_ON_PAGE(PageTail(page), page); > + VM_BUG_ON_PAGE(!PageAnon(page), page); > + ClearPageSwapBacked(page); > +} > + > +static __always_inline void ClearPageLazyFree(struct page *page) > +{ > + VM_BUG_ON_PAGE(PageTail(page), page); > + VM_BUG_ON_PAGE(!PageAnon(page), page); > + SetPageSwapBacked(page); > +} These BUG_ONs aren't present in the current code and are unchangelogged. And they aren't free! before: q:/usr/src/25> size -t mm/rmap.o mm/swap.o mm/vmscan.o text data bss dec hex filename 41580 4211 192 45983 b39f mm/rmap.o 50684 9259 1184 61127 eec7 mm/swap.o 117728 46775 128 164631 28317 mm/vmscan.o 209992 60245 1504 271741 4257d (TOTALS) after: text data bss dec hex filename 42035 4299 192 46526 b5be mm/rmap.o 51091 9347 1184 61622 f0b6 mm/swap.o 118132 46775 128 165035 284ab mm/vmscan.o 211258 60421 1504 273183 42b1f (TOTALS) ALso, if they actually trigger, Linus goes berserk. If you have some special reason to add these assertions, please do it as a (changelogged!) followup patch and I'll keep it as a linux-next only thing.