Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753098AbdGIWt0 (ORCPT ); Sun, 9 Jul 2017 18:49:26 -0400 Received: from mail-pg0-f48.google.com ([74.125.83.48]:36452 "EHLO mail-pg0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753025AbdGIWtY (ORCPT ); Sun, 9 Jul 2017 18:49:24 -0400 From: Joel Fernandes To: linux-kernel@vger.kernel.org Cc: Joel Fernandes , Alexander Duyck , Mel Gorman , Hao Lee , Vladimir Davydov , Johannes Weiner , Joonsoo Kim , Steven Rostedt , linux-mm@kvack.org Subject: [RFC v1 2/2] tracing/ring_buffer: Try harder to allocate Date: Sun, 9 Jul 2017 15:49:11 -0700 Message-Id: <20170709224911.13030-2-joelaf@google.com> X-Mailer: git-send-email 2.13.2.725.g09c95d1e9-goog In-Reply-To: <20170709224911.13030-1-joelaf@google.com> References: <20170709224911.13030-1-joelaf@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2260 Lines: 54 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_DONTOOM flag introduced in earlier patches while droppping __GFP_NORETRY. With this the following succeed without destabilizing a system with 8 CPU cores and 4GB of memory: echo 100000 > /sys/kernel/debug/tracing/buffer_size_kb On an 8-core system, that would allocate ~800MB. Cc: Alexander Duyck Cc: Mel Gorman Cc: Hao Lee Cc: Vladimir Davydov Cc: Johannes Weiner Cc: Joonsoo Kim Cc: Steven Rostedt Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Joel Fernandes --- kernel/trace/ring_buffer.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 4ae268e687fe..b1cdcac6ca89 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1141,7 +1141,7 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) * not destabilized. */ bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), - GFP_KERNEL | __GFP_NORETRY, + GFP_KERNEL | __GFP_DONTOOM, cpu_to_node(cpu)); if (!bpage) goto free_pages; @@ -1149,7 +1149,7 @@ static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) list_add(&bpage->list, pages); page = alloc_pages_node(cpu_to_node(cpu), - GFP_KERNEL | __GFP_NORETRY, 0); + GFP_KERNEL | __GFP_DONTOOM, 0); if (!page) goto free_pages; bpage->page = page_address(page); -- 2.13.2.725.g09c95d1e9-goog