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Wed, 17 Feb 2021 16:51:29 +0000 (UTC) Received: from [10.36.114.178] (ovpn-114-178.ams2.redhat.com [10.36.114.178]) by smtp.corp.redhat.com (Postfix) with ESMTP id DDF9F10013D7; Wed, 17 Feb 2021 16:51:27 +0000 (UTC) To: Minchan Kim , Andrew Morton Cc: linux-mm , LKML , mhocko@suse.com, joaodias@google.com References: <20210217163603.429062-1-minchan@kernel.org> From: David Hildenbrand Organization: Red Hat GmbH Subject: Re: [PATCH] mm: be more verbose for alloc_contig_range faliures Message-ID: <854d4ec8-1eb9-3595-b867-3e50f5a0e6a8@redhat.com> Date: Wed, 17 Feb 2021 17:51:27 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210217163603.429062-1-minchan@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: CF971138 X-Stat-Signature: c9wz3paetkp6sqtx3rwxpcekq4kzqbar Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf12; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=63.128.21.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1613580689-148679 Content-Transfer-Encoding: quoted-printable 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 17.02.21 17:36, Minchan Kim wrote: > alloc_contig_range is usually used on cma area or movable zone. > It's critical if the page migration fails on those areas so > dump more debugging message like memory_hotplug unless user > specifiy __GFP_NOWARN. >=20 > Signed-off-by: Minchan Kim > --- > mm/page_alloc.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) >=20 > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 0b55c9c95364..67f3ee3a1528 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8486,6 +8486,15 @@ static int __alloc_contig_migrate_range(struct c= ompact_control *cc, > NULL, (unsigned long)&mtc, cc->mode, MR_CONTIG_RANGE); > } > if (ret < 0) { > + if (!(cc->gfp_mask & __GFP_NOWARN)) { > + struct page *page; > + > + list_for_each_entry(page, &cc->migratepages, lru) { > + pr_warn("migrating pfn %lx failed ret:%d ", > + page_to_pfn(page), ret); > + dump_page(page, "migration failure"); > + } This can create *a lot* of noise. For example, until huge pages are=20 actually considered, we will choke on each end every huge page - and=20 might do so over and over again. This might be helpful for debugging, but is unacceptable for production=20 systems for now I think. Maybe for now, do it based on CONFIG_DEBUG_VM. > + } > putback_movable_pages(&cc->migratepages); > return ret; > } > @@ -8728,6 +8737,8 @@ struct page *alloc_contig_pages(unsigned long nr_= pages, gfp_t gfp_mask, > pfn =3D ALIGN(zone->zone_start_pfn, nr_pages); > while (zone_spans_last_pfn(zone, pfn, nr_pages)) { > if (pfn_range_valid_contig(zone, pfn, nr_pages)) { > + unsigned long gfp_flags; > + > /* > * We release the zone lock here because > * alloc_contig_range() will also lock the zone > @@ -8736,8 +8747,11 @@ struct page *alloc_contig_pages(unsigned long nr= _pages, gfp_t gfp_mask, > * and cause alloc_contig_range() to fail... > */ > spin_unlock_irqrestore(&zone->lock, flags); > + > + if (zone_idx(zone) !=3D ZONE_MOVABLE) > + gfp_flags =3D gfp_mask | __GFP_NOWARN; This feels wrong. It might be better to make that decision inside=20 __alloc_contig_migrate_range() based on cc->zone. --=20 Thanks, David / dhildenb