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Wed, 10 Mar 2021 16:10:27 -0800 (PST) Received: from google.com ([2620:15c:211:201:64cb:74c7:f2c:e5e0]) by smtp.gmail.com with ESMTPSA id q15sm464043pje.28.2021.03.10.16.10.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Mar 2021 16:10:26 -0800 (PST) Date: Wed, 10 Mar 2021 16:10:24 -0800 From: Minchan Kim To: Andrew Morton Cc: linux-mm , LKML , John Dias , Michal Hocko , David Hildenbrand , Jason Baron Subject: Re: [PATCH v3] mm: page_alloc: dump migrate-failed pages Message-ID: References: <20210310180104.517886-1-minchan@kernel.org> <20210310125609.359888dc65562fbed4b1f088@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210310125609.359888dc65562fbed4b1f088@linux-foundation.org> X-Stat-Signature: scdpyazs3zchm6mh5wizx3cwoj7x86th X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 6580EDD Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf29; identity=mailfrom; envelope-from=""; helo=mail-pg1-f176.google.com; client-ip=209.85.215.176 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615421425-353482 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 Wed, Mar 10, 2021 at 12:56:09PM -0800, Andrew Morton wrote: > On Wed, 10 Mar 2021 10:01:04 -0800 Minchan Kim wrote: > > > Currently, debugging CMA allocation failures is quite limited. > > The most commong source of these failures seems to be page > > migration which doesn't provide any useful information on the > > reason of the failure by itself. alloc_contig_range can report > > those failures as it holds a list of migrate-failed pages. > > > > page refcount, mapcount with page flags on dump_page are > > helpful information to deduce the culprit. Furthermore, > > dump_page_owner was super helpful to find long term pinner > > who initiated the page allocation. > > > > The reason it approach with dynamic debug is the debug message > > could emit lots of noises as alloc_contig_range calls more > > frequently since it's a best effort allocator. > > > > There are two ifdefery conditions to support common dyndbg options: > > > > - CONFIG_DYNAMIC_DEBUG_CORE && DYNAMIC_DEBUG_MODULE > > It aims for supporting the feature with only specific file > > with adding ccflags. > > > > - CONFIG_DYNAMIC_DEBUG > > It aims for supporting the feature with system wide globally. > > > > A simple example to enable the feature: > > > > Admin could enable the dump like this(by default, disabled) > > > > echo "func dump_migrate_failure_pages +p" > control > > > > Admin could disable it. > > > > echo "func dump_migrate_failure_pages =_" > control > > I think the changelog is out of sync. Did you mean > "alloc_contig_dump_pages" here? Oops. Now fixed. > > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -8453,6 +8453,27 @@ static unsigned long pfn_max_align_up(unsigned long pfn) > > pageblock_nr_pages)); > > } > > > +#if defined(CONFIG_DYNAMIC_DEBUG) || \ > > + (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE)) > > +static void alloc_contig_dump_pages(struct list_head *page_list) > > +{ > > + DEFINE_DYNAMIC_DEBUG_METADATA(descriptor, > > + "migrate failure"); > > + > > + if (DYNAMIC_DEBUG_BRANCH(descriptor)) { > > + struct page *page; > > + > > + WARN(1, "failed callstack"); > > + list_for_each_entry(page, page_list, lru) > > + dump_page(page, "migration failure"); > > + } > > +} > > I doubt if everyone is familiar with dynamic debug. It might be kind > to add a little comment over this, telling people how to turn it on and > off. Something like this? #if defined(CONFIG_DYNAMIC_DEBUG) || \ (defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE)) /* * dyndbg_dir="/sys/kernel/debug/dynamic_debug" * To enable: * echo "func dump_migrate_failure_pages +p" > $dyndbg_dir/control * To disable: * echo "func dump_migrate_failure_pages =_" > $dyndbg_dir/control */