On Tue, Jul 3, 2018 at 12:25 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Tue, Jul 03, 2018 at 12:19:35PM -0700, Shakeel Butt wrote: > > On Tue, Jul 3, 2018 at 12:13 PM Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> wrote: > > > > Do we really have so very many !memcg-aware shrinkers? > > > > > > > > $ git grep -w register_shrinker |wc > > > > 32 119 2221 > > > > $ git grep -w register_shrinker_prepared |wc > > > > 4 13 268 > > > > (that's an overstatement; one of those is the declaration, one the definition, > > > > and one an internal call, so we actually only have one caller of _prepared). > > > > > > > > So it looks to me like your average system has one shrinker per > > > > filesystem, one per graphics card, one per raid5 device, and a few > > > > miscellaneous. I'd be shocked if anybody had more than 100 shrinkers > > > > registered on their laptop. > > > > > > > > I think we should err on the side of simiplicity and just have one IDR for > > > > every shrinker instead of playing games to solve a theoretical problem. > > > > > > It just a standard situation for the systems with many containers. Every mount > > > introduce a new shrinker to the system, so it's easy to see a system with > > > 100 or ever 1000 shrinkers. AFAIR, Shakeel said he also has the similar > > > configurations. > > > > > > > I can say on our production systems, a couple thousand shrinkers is normal. > > But how many are !memcg aware? It sounds to me like almost all of the > shrinkers come through the sget_userns() caller, so the other shrinkers > are almost irrelevant. I would say almost half. Sorry I do not have exact numbers. Basically we use ext4 very extensively and majority of shrinkers are related to ext4 (again I do not have exact numbers). One ext4 mount typically registers three shrinkers, one memcg-aware (sget) and two non-memcg aware (ext4_es_register_shrinker, ext4_xattr_create_cache). Shakeel
