Commits
Joel Fernandes committed 848618857d2
tracing/ring_buffer: Try harder to allocate 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 Link: http://lkml.kernel.org/r/20170713021416.8897-1-joelaf@google.com Cc: Tim Murray <timmurray@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@kernel.org> Signed-off-by: Joel Fernandes <joelaf@google.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>