Commit b2a209ff authored by Committed by Linus Torvalds
Revert "kernfs: do not account ino_ida allocations to memcg"
Currently, all kmem allocations (namely every kmem_cache_alloc, kmalloc, alloc_kmem_pages call) are accounted to memory cgroup automatically. Callers have to explicitly opt out if they don't want/need accounting for some reason. Such a design decision leads to several problems: - kmalloc users are highly sensitive to failures, many of them implicitly rely on the fact that kmalloc never fails, while memcg makes failures quite plausible. - A lot of objects are shared among different containers by design. Accounting such objects to one of containers is just unfair. Moreover, it might lead to pinning a dead memcg along with its kmem caches, which aren't tiny, which might result in noticeable increase in memory consumption for no apparent reason in the long run. - There are tons of short-lived objects. Accounting them to memcg will only result in slight noise and won't change the overall picture, but we still have to pay accounting overhead. For more info, see - http://lkml.kernel.org/r/20151105144002.GB15111%40dhcp22.suse.cz - http://lkml.kernel.org/r/20151106090555.GK29259@esperanza Therefore this patchset switches to the white list policy. Now kmalloc users have to explicitly opt in by passing __GFP_ACCOUNT flag. Currently, the list of accounted objects is quite limited and only includes those allocations that (1) are known to be easily triggered from userspace and (2) can fail gracefully (for the full list see patch no. 6) and it still misses many object types. However, accounting only those objects should be a satisfactory approximation of the behavior we used to have for most sane workloads. This patch (of 6): Revert 499611ed ("kernfs: do not account ino_ida allocations to memcg"). Black-list kmem accounting policy (aka __GFP_NOACCOUNT) turned out to be fragile and difficult to maintain, because there seem to be many more allocations that should not be accounted than those that should be. Besides, false accounting an allocation might result in much worse consequences than not accounting at all, namely increased memory consumption due to pinned dead kmem caches. So it was decided to switch to the white-list policy. This patch reverts bits introducing the black-list policy. The white-list policy will be introduced later in the series. Signed-off-by: Vladimir Davydov <firstname.lastname@example.org> Acked-by: Johannes Weiner <email@example.com> Cc: Michal Hocko <firstname.lastname@example.org> Cc: Tejun Heo <email@example.com> Cc: Greg Thelen <firstname.lastname@example.org> Cc: Christoph Lameter <email@example.com> Cc: Pekka Enberg <firstname.lastname@example.org> Cc: David Rientjes <email@example.com> Cc: Joonsoo Kim <firstname.lastname@example.org> Signed-off-by: Andrew Morton <email@example.com> Signed-off-by: Linus Torvalds <firstname.lastname@example.org>
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