On Mon, Jul 10, 2017 at 11:05:00PM -0700, Joel Fernandes wrote: > ftrace can fail to allocate per-CPU ring buffer on systems with a large > number of CPUs coupled while large amounts of cache happening in the > page cache. Currently the ring buffer allocation doesn't retry in the VM > implementation even if direct-reclaim made some progress but still > wasn't able to find a free page. On retrying I see that the allocations > almost always succeed. The retry doesn't happen because __GFP_NORETRY is > used in the tracer to prevent the case where we might OOM, however if we > drop __GFP_NORETRY, we risk destabilizing the system if OOM killer is > triggered. To prevent this situation, use the __GFP_RETRY_MAYFAIL flag > introduced recently [1]. > > Tested the following still succeeds without destabilizing a system with > 1GB memory. > echo 300000 > /sys/kernel/debug/tracing/buffer_size_kb > > [1] https://marc.info/?l=linux-mm&m=149820805124906&w=2 > > Cc: Alexander Duyck <[email protected]> > Cc: Mel Gorman <[email protected]> > Cc: Hao Lee <[email protected]> > Cc: Vladimir Davydov <[email protected]> > Cc: Johannes Weiner <[email protected]> > Cc: Joonsoo Kim <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Tim Murray <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: [email protected] > Signed-off-by: Joel Fernandes <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
