On Mon, May 14, 2018 at 12:03:38PM +0300, Kirill Tkhai wrote: > On 13.05.2018 08:15, Vladimir Davydov wrote: > > On Thu, May 10, 2018 at 12:52:18PM +0300, Kirill Tkhai wrote: > >> The patch introduces shrinker::id number, which is used to enumerate > >> memcg-aware shrinkers. The number start from 0, and the code tries > >> to maintain it as small as possible. > >> > >> This will be used as to represent a memcg-aware shrinkers in memcg > >> shrinkers map. > >> > >> Since all memcg-aware shrinkers are based on list_lru, which is per-memcg > >> in case of !SLOB only, the new functionality will be under MEMCG && !SLOB > >> ifdef (symlinked to CONFIG_MEMCG_SHRINKER). > > > > Using MEMCG && !SLOB instead of introducing a new config option was done > > deliberately, see: > > > > http://lkml.kernel.org/r/20151210202244.GA4809@xxxxxxxxxxx > > > > I guess, this doesn't work well any more, as there are more and more > > parts depending on kmem accounting, like shrinkers. If you really want > > to introduce a new option, I think you should call it CONFIG_MEMCG_KMEM > > and use it consistently throughout the code instead of MEMCG && !SLOB. > > And this should be done in a separate patch. > > What do you mean under "consistently throughout the code"? Should I replace > all MEMCG && !SLOB with CONFIG_MEMCG_KMEM over existing code? Yes, otherwise it looks messy - in some places we check !SLOB, in others we use CONFIG_MEMCG_SHRINKER (or whatever it will be called). > > >> diff --git a/fs/super.c b/fs/super.c > >> index 122c402049a2..16c153d2f4f1 100644 > >> --- a/fs/super.c > >> +++ b/fs/super.c > >> @@ -248,6 +248,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags, > >> s->s_time_gran = 1000000000; > >> s->cleancache_poolid = CLEANCACHE_NO_POOL; > >> > >> +#ifdef CONFIG_MEMCG_SHRINKER > >> + s->s_shrink.id = -1; > >> +#endif > > > > No point doing that - you are going to overwrite the id anyway in > > prealloc_shrinker(). > > Not so, this is done deliberately. alloc_super() has the only "fail" label, > and it handles all the allocation errors there. The patch just behaves in > the same style. It sets "-1" to make destroy_unused_super() able to differ > the cases, when shrinker is really initialized, and when it's not. > If you don't like this, I can move "s->s_shrink.id = -1;" into > prealloc_memcg_shrinker() instead of this. Yes, please do so that we don't have MEMCG ifdefs in fs code. Thanks.
