On Fri, Apr 30, 2021 at 12:01 AM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > From: Minchan Kim <minchan@xxxxxxxxxx> > Subject: mm: page_alloc: dump migrate-failed pages > > Currently, debugging CMA allocation failures is quite limited. The most > common 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. > > The information logged by dump_page() has already proven helpful for > debugging allocation issues, like identifying long-term pinnings on > ZONE_MOVABLE or MIGRATE_CMA. > > Let's use the dynamic debugging infrastructure, such that we avoid > flooding the logs and creating a lot of noise on frequent > alloc_contig_range() calls. This information is helpful for debugging > only. > > 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 alloc_contig_dump_pages +p" > control > > Admin could disable it. > > echo "func alloc_contig_dump_pages =_" > control > > Detail goes Documentation/admin-guide/dynamic-debug-howto.rst > > A concern is utility functions in dump_page use inconsistent > loglevels. In the future, we might want to make the loglevels > used inside dump_page() consistent and eventually rework the way > we log the information here. See [1]. > FWIW, the "format ^$prefix" specifier allows selection of "classes" of pr_debugs examples: "^drm:kms:" etc "^drm:" too, for example to set +fmlt across entire subsystem "gvt:" "^Lo", "^MID", "^HI" "^1:", "^2:", "^3:" all hierarchy / set-creation is applied by authors
