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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E71FAC54EE9 for ; Tue, 13 Sep 2022 07:59:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231308AbiIMH7L (ORCPT ); Tue, 13 Sep 2022 03:59:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44044 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229821AbiIMH7H (ORCPT ); Tue, 13 Sep 2022 03:59:07 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D85345A3C0 for ; Tue, 13 Sep 2022 00:59:05 -0700 (PDT) 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=ZSuHqErBdLq/WjJ+4mcD880q8RV5cT2VvtIHCgGu7tA=; b=XKsiu+BkB0bgK7rldV7WiuPw5j e66tuTB0BowARIzVPTyQblNFQnpVVLLnFOW70jgMgJRCelISL57ZGUGsuG9B/hSGvZwCrNDqJYi3V wQntdW3RfHV800/1iU4ZBPCSYkRzPDa2goPomk3ijOTcBrahxNxz3sUiiv1PSaijRi6Sdr51LbQBt 40k6K/mBev1+LP+HHeHoArRbGWNmSEMP/sPHZ3OHKO0CqL3kRKjYDhCoE449sFZOco5xjQ6oWTdeL 8gKb6s7WQH3pCqcKYDrNLCnOIZOz9aI+cpiqbrTmBnGP3eZx++sp4ZifobZk32K4gaONjb3jJqfvQ XsX7HcXQ==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1oY0op-00GhZw-Km; Tue, 13 Sep 2022 07:58:55 +0000 Date: Tue, 13 Sep 2022 08:58:55 +0100 From: Matthew Wilcox To: Anshuman Khandual Cc: Miaohe Lin , akpm@linux-foundation.org, david@redhat.com, osalvador@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 01/16] mm/page_alloc: ensure kswapd doesn't accidentally go to sleep Message-ID: References: <20220909092451.24883-1-linmiaohe@huawei.com> <20220909092451.24883-2-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 13, 2022 at 12:32:50PM +0530, Anshuman Khandual wrote: > > > On 9/9/22 14:54, Miaohe Lin wrote: > > If ALLOC_KSWAPD is set, wake_all_kswapds() will be called to ensure > > kswapd doesn't accidentally go to sleep. But when reserve_flags is > > set, alloc_flags will be overwritten and ALLOC_KSWAPD is thus lost. > > Preserve the ALLOC_KSWAPD flag in alloc_flags to ensure kswapd won't > > go to sleep accidentally. > > Currently wake_all_kswapds() gets skipped subsequently if ALLOC_KSWAPD > is lost, but this only happens when the 'retry:' loops is taken ? Right, but see the comment: /* Ensure kswapd doesn't accidentally go to sleep as long as we loop */ and that is not currently true. I think that was an inadvertent change. Particularly since the changelog for 0a79cdad5eb2 says "No functional change". > > > > Fixes: 0a79cdad5eb2 ("mm: use alloc_flags to record if kswapd can wake") > > Signed-off-by: Miaohe Lin > > --- > > mm/page_alloc.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index ba5c9402a5cb..4b97a03fa2dd 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -5147,7 +5147,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > > > > reserve_flags = __gfp_pfmemalloc_flags(gfp_mask); > > if (reserve_flags) > > - alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags); > > + alloc_flags = gfp_to_alloc_flags_cma(gfp_mask, reserve_flags) | > > + (alloc_flags & ALLOC_KSWAPD); > > > > /* > > * Reset the nodemask and zonelist iterators if memory policies can be >