Revert "memcg: enable accounting for pollfd and select bits arrays"

Revert "memcg: enable accounting for pollfd and select bits arrays"

This reverts commit 9e55b434b578c66aaeb1f99f883df8aa68cef90b.

Just like with the memcg lock accounting, the kernel test robot reports
a sizeable performance regression for this commit, and while it clearly
does the rigth thing in theory, we'll need to look at just how to avoid
or minimize the performance overhead of the memcg accounting.

People already have suggestions on how to do that, but it's "future
work".

So revert it for now.

[ Note: the first link below is for this same commit but a different
  commit ID, because it's the kernel test robot ended up noticing it in
  Andrew Morton's patch queue ]

Link: https://lore.kernel.org/lkml/20210905132732.GC15026@xsang-OptiPlex-9020/
Link: https://lore.kernel.org/lkml/20210907150757.GE17617@xsang-OptiPlex-9020/
Acked-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>