On Wed 31-07-19 16:44:50, Catalin Marinas wrote: > On Tue, Jul 30, 2019 at 01:02:15PM -0700, Andrew Morton wrote: > > On Sat, 27 Jul 2019 14:23:33 +0100 Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > > > > Add mempool allocations for struct kmemleak_object and > > > kmemleak_scan_area as slightly more resilient than kmem_cache_alloc() > > > under memory pressure. Additionally, mask out all the gfp flags passed > > > to kmemleak other than GFP_KERNEL|GFP_ATOMIC. > > > > > > A boot-time tuning parameter (kmemleak.mempool) is added to allow a > > > different minimum pool size (defaulting to NR_CPUS * 4). > > > > btw, the checkpatch warnings are valid: > > > > WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc > > #70: FILE: mm/kmemleak.c:197: > > +static int min_object_pool = NR_CPUS * 4; > > > > WARNING: usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc > > #71: FILE: mm/kmemleak.c:198: > > +static int min_scan_area_pool = NR_CPUS * 1; > > > > There can be situations where NR_CPUS is much larger than > > num_possible_cpus(). Can we initialize these tunables within > > kmemleak_init()? > > We could and, at least on arm64, cpu_possible_mask is already > initialised at that point. However, that's a totally made up number. I > think we would better go for a Kconfig option (defaulting to, say, 1024) > similar to the CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE and we grow it if > people report better values in the future. If you really want/need to make this configurable then the command line parameter makes more sense - think of distribution kernel users for example. But I am still not sure why this is really needed. The initial size is a "made up" number of course. There is no good estimation to make (without a crystal ball). The value might be increased based on real life usage. -- Michal Hocko SUSE Labs
