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  1. Feb 11, 2021
  3. Feb 10, 2021
    • David S. Miller's avatar
      Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf · b8776f14
      David S. Miller authored 
      

Daniel Borkmann says:

====================
pull-request: bpf 2021-02-10

The following pull-request contains BPF updates for your *net* tree.

We've added 5 non-merge commits during the last 8 day(s) which contain
a total of 3 files changed, 22 insertions(+), 21 deletions(-).

The main changes are:

1) Fix missed execution of kprobes BPF progs when kprobe is firing via
   int3, from Alexei Starovoitov.

2) Fix potential integer overflow in map max_entries for stackmap on
   32 bit archs, from Bui Quang Minh.

3) Fix a verifier pruning and a insn rewrite issue related to 32 bit ops,
   from Daniel Borkmann.
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
c# Please enter a commit message to explain why this merge is necessary,
      b8776f14
    • Johannes Weiner's avatar
      Revert "mm: memcontrol: avoid workload stalls when lowering memory.high" · e82553c1
      Johannes Weiner authored 
      This reverts commit 536d3bf2, as it can
cause writers to memory.high to get stuck in the kernel forever,
performing page reclaim and consuming excessive amounts of CPU cycles.

Before the patch, a write to memory.high would first put the new limit
in place for the workload, and then reclaim the requested delta.  After
the patch, the kernel tries to reclaim the delta before putting the new
limit into place, in order to not overwhelm the workload with a sudden,
large excess over the limit.  However, if reclaim is actively racing
with new allocations from the uncurbed workload, it can keep the write()
working inside the kernel indefinitely.

This is causing problems in Facebook production.  A privileged
system-level daemon that adjusts memory.high for various workloads
running on a host can get unexpectedly stuck in the kernel and
essentially turn into a sort of involuntary kswapd for one of the
workloads.  We've observed that daemon busy-spin in a write() for
minutes at a time, neglecting its other duties on the system, and
expending privileged system resources on behalf of a workload.

To remedy this, we have first considered changing the reclaim logic to
break out after a couple of loops - whether the workload has converged
to the new limit or not - and bound the write() call this way.  However,
the root cause that inspired the sequence change in the first place has
been fixed through other means, and so a revert back to the proven
limit-setting sequence, also used by memory.max, is preferable.

The sequence was changed to avoid extreme latencies in the workload when
the limit was lowered: the sudden, large excess created by the limit
lowering would erroneously trigger the penalty sleeping code that is
meant to throttle excessive growth from below.  Allocating threads could
end up sleeping long after the write() had already reclaimed the delta
for which they were being punished.

However, erroneous throttling also caused problems in other scenarios at
around the same time.  This resulted in commit b3ff9291 ("mm, memcg:
reclaim more aggressively before high allocator throttling"), included
in the same release as the offending commit.  When allocating threads
now encounter large excess caused by a racing write() to memory.high,
instead of entering punitive sleeps, they will simply be tasked with
helping reclaim down the excess, and will be held no longer than it
takes to accomplish that.  This is in line with regular limit
enforcement - i.e.  if the workload allocates up against or over an
otherwise unchanged limit from below.

With the patch breaking userspace, and the root cause addressed by other
means already, revert it again.

Link: https://lkml.kernel.org/r/20210122184341.292461-1-hannes@cmpxchg.org
Fixes: 536d3bf2

 ("mm: memcontrol: avoid workload stalls when lowering memory.high")
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reported-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarChris Down <chris@chrisdown.name>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: <stable@vger.kernel.org>	[5.8+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      e82553c1
    • Andrey Ryabinin's avatar
      MAINTAINERS: update Andrey Ryabinin's email address · a0c2eb0a
      Andrey Ryabinin authored 
      Update my email, @virtuozzo.com will stop working shortly.

Link: https://lkml.kernel.org/r/20210204223904.3824-1-ryabinin.a.a@gmail.com


Signed-off-by: default avatarAndrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      a0c2eb0a