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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>
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5771a8c088
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1 changed files with 5 additions and 5 deletions
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@ -1136,12 +1136,12 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
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for (i = 0; i < nr_pages; i++) {
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struct page *page;
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/*
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* __GFP_NORETRY flag makes sure that the allocation fails
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* gracefully without invoking oom-killer and the system is
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* not destabilized.
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* __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
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* gracefully without invoking oom-killer and the system is not
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* destabilized.
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*/
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bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
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GFP_KERNEL | __GFP_NORETRY,
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GFP_KERNEL | __GFP_RETRY_MAYFAIL,
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cpu_to_node(cpu));
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if (!bpage)
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goto free_pages;
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@ -1149,7 +1149,7 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu)
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list_add(&bpage->list, pages);
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page = alloc_pages_node(cpu_to_node(cpu),
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GFP_KERNEL | __GFP_NORETRY, 0);
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GFP_KERNEL | __GFP_RETRY_MAYFAIL, 0);
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if (!page)
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goto free_pages;
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bpage->page = page_address(page);
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