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 B75EEC5479D for ; Wed, 11 Jan 2023 15:36:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232153AbjAKPgN (ORCPT ); Wed, 11 Jan 2023 10:36:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59364 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233100AbjAKPgK (ORCPT ); Wed, 11 Jan 2023 10:36:10 -0500 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DCD4B193D4 for ; Wed, 11 Jan 2023 07:36:04 -0800 (PST) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id A58544C9F; Wed, 11 Jan 2023 15:36:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1673451362; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=nRH21KYwjUTBDhGKpPMV5E370DEd1Sm0RKzqrNyyp7k=; b=LBbLmLMOPkJcUSIZBVyYh9fnucdZiPquR9gDpo20B4LC97zeqTL3kZdEp5WNo7NK9zWm1U J0qc2+/QjMOdTTRKHmRw3JeY7uMa9w1AVMtpq9lrN25SYUi4QU37/SMM2VaUk3gxpwHw+3 jLyAMD/CkOp40WbWNC8/1rHcCB9YTWI= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 876D11358A; Wed, 11 Jan 2023 15:36:02 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 9I4qHmLXvmNfNwAAMHmgww (envelope-from ); Wed, 11 Jan 2023 15:36:02 +0000 Date: Wed, 11 Jan 2023 16:36:01 +0100 From: Michal Hocko To: Mel Gorman Cc: Linux-MM , Andrew Morton , NeilBrown , Thierry Reding , Matthew Wilcox , Vlastimil Babka , LKML Subject: Re: [PATCH 3/7] mm/page_alloc: Explicitly record high-order atomic allocations in alloc_flags Message-ID: References: <20230109151631.24923-1-mgorman@techsingularity.net> <20230109151631.24923-4-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230109151631.24923-4-mgorman@techsingularity.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 09-01-23 15:16:27, Mel Gorman wrote: > A high-order ALLOC_HARDER allocation is assumed to be atomic. While that > is accurate, it changes later in the series. In preparation, explicitly > record high-order atomic allocations in gfp_to_alloc_flags(). There is > a slight functional change in that OOM handling avoids using high-order > reserve until it has to. I do not follow the oom handling part. IIRC we are dropping highatomic reserves before triggering oom. Something might have changed down the path but I can still see unreserve_highatomic_pageblock in should_reclaim_retry. I do not have any objection to ALLOC_HIGHATOMIC itself, though. > Signed-off-by: Mel Gorman > --- > mm/internal.h | 1 + > mm/page_alloc.c | 29 +++++++++++++++++++++++------ > 2 files changed, 24 insertions(+), 6 deletions(-) > > diff --git a/mm/internal.h b/mm/internal.h > index 403e4386626d..178484d9fd94 100644 > --- a/mm/internal.h > +++ b/mm/internal.h > @@ -746,6 +746,7 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone, > #else > #define ALLOC_NOFRAGMENT 0x0 > #endif > +#define ALLOC_HIGHATOMIC 0x200 /* Allows access to MIGRATE_HIGHATOMIC */ > #define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */ > > enum ttu_flags; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0040b4e00913..0ef4f3236a5a 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3706,10 +3706,20 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, > * reserved for high-order atomic allocation, so order-0 > * request should skip it. > */ > - if (order > 0 && alloc_flags & ALLOC_HARDER) > + if (alloc_flags & ALLOC_HIGHATOMIC) > page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); > if (!page) { > page = __rmqueue(zone, order, migratetype, alloc_flags); > + > + /* > + * If the allocation fails, allow OOM handling access > + * to HIGHATOMIC reserves as failing now is worse than > + * failing a high-order atomic allocation in the > + * future. > + */ > + if (!page && (alloc_flags & ALLOC_OOM)) > + page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); > + > if (!page) { > spin_unlock_irqrestore(&zone->lock, flags); > return NULL; > @@ -4023,8 +4033,10 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > return true; > } > #endif > - if (alloc_harder && !free_area_empty(area, MIGRATE_HIGHATOMIC)) > + if ((alloc_flags & (ALLOC_HIGHATOMIC|ALLOC_OOM)) && > + !free_area_empty(area, MIGRATE_HIGHATOMIC)) { > return true; > + } > } > return false; > } > @@ -4286,7 +4298,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, > * If this is a high-order atomic allocation then check > * if the pageblock should be reserved for the future > */ > - if (unlikely(order && (alloc_flags & ALLOC_HARDER))) > + if (unlikely(alloc_flags & ALLOC_HIGHATOMIC)) > reserve_highatomic_pageblock(page, zone, order); > > return page; > @@ -4813,7 +4825,7 @@ static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask, > } > > static inline unsigned int > -gfp_to_alloc_flags(gfp_t gfp_mask) > +gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order) > { > unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET; > > @@ -4839,8 +4851,13 @@ gfp_to_alloc_flags(gfp_t gfp_mask) > * Not worth trying to allocate harder for __GFP_NOMEMALLOC even > * if it can't schedule. > */ > - if (!(gfp_mask & __GFP_NOMEMALLOC)) > + if (!(gfp_mask & __GFP_NOMEMALLOC)) { > alloc_flags |= ALLOC_HARDER; > + > + if (order > 0) > + alloc_flags |= ALLOC_HIGHATOMIC; > + } > + > /* > * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the > * comment for __cpuset_node_allowed(). > @@ -5048,7 +5065,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > * kswapd needs to be woken up, and to avoid the cost of setting up > * alloc_flags precisely. So we do that now. > */ > - alloc_flags = gfp_to_alloc_flags(gfp_mask); > + alloc_flags = gfp_to_alloc_flags(gfp_mask, order); > > /* > * We need to recalculate the starting point for the zonelist iterator > -- > 2.35.3 -- Michal Hocko SUSE Labs