From: Steven Rostedt The splice code allocates a page even when the ring buffer is empty. It detects the ring buffer being empty when it it fails to copy anything from the ring buffer into the page. This patch adds a check to see if there is anything in the ring buffer before allocating a page. Thanks to logdev for letting me trace the tracer to find this. [ Impact: speed up due to removing unnecessary allocation ] Signed-off-by: Steven Rostedt --- kernel/trace/trace.c | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 9058240..0aeb3b9 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3508,7 +3508,7 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, .spd_release = buffer_spd_release, }; struct buffer_ref *ref; - int size, i; + int entries, size, i; size_t ret; if (*ppos & (PAGE_SIZE - 1)) { @@ -3523,7 +3523,9 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, len &= PAGE_MASK; } - for (i = 0; i < PIPE_BUFFERS && len; i++, len -= PAGE_SIZE) { + entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu); + + for (i = 0; i < PIPE_BUFFERS && len && entries; i++, len -= PAGE_SIZE) { struct page *page; int r; @@ -3564,6 +3566,8 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos, spd.partial[i].private = (unsigned long)ref; spd.nr_pages++; *ppos += PAGE_SIZE; + + entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu); } spd.nr_pages = i; -- 1.6.2.1 -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/