ftrace: Allow stealing pages from pipe buffer
authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Thu, 9 Aug 2012 12:31:10 +0000 (21:31 +0900)
committerRusty Russell <rusty@rustcorp.com.au>
Fri, 28 Sep 2012 05:35:12 +0000 (15:05 +0930)
commitd55cb6cf143ae16eaa415baab520b8eaf4a1012f
tree449f118e54bc77d753e319fb5a5294611b86c36d
parentefe75d24a69fc39bb09d882ca2d5b90d4da02afe
ftrace: Allow stealing pages from pipe buffer

Use generic steal operation on pipe buffer to allow stealing
ring buffer's read page from pipe buffer.

Note that this could reduce the performance of splice on the
splice_write side operation without affinity setting.
Since the ring buffer's read pages are allocated on the
tracing-node, but the splice user does not always execute
splice write side operation on the same node. In this case,
the page will be accessed from the another node.
Thus, it is strongly recommended to assign the splicing
thread to corresponding node.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
kernel/trace/trace.c