linux-kernel - Re: [RFC] perf: perf record sets inherit by default

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Date:	Mon, 17 May 2010 18:48:00 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	mingo@...e.hu, Paul Mackerras <paulus@...ba.org>,
	"David S. Miller" <davem@...emloft.net>,
	perfmon2-devel@...ts.sf.net
Subject: Re: [RFC] perf: perf record sets inherit by default

On Mon, 2010-05-17 at 16:25 +0200, Stephane Eranian wrote:
> > Right, but I think the default of inherit is right, and once you do that
> > you basically have to do the per-task-per-cpu thing, otherwise your
> > fancy 16-way will start spending most of its time in cacheline bounces.
> >
> In that case, don't you think you should also ensure that the buffer is
> allocated on the NUMA node of the designated per-thread-per-cpu?
> I don't think it is the case today.

Yeah, something like the below ought to do I guess..

Almost-Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 kernel/perf_event.c |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 9dbe8cd..85e2d32 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2288,6 +2288,19 @@ perf_mmap_to_page(struct perf_mmap_data *data, unsigned long pgoff)
 	return virt_to_page(data->data_pages[pgoff - 1]);
 }
 
+static void *perf_mmap_alloc_page(int cpu)
+{
+	struct page *page;
+	int node;
+
+	node = (cpu == -1) ? cpu : cpu_to_node(cpu);
+	page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
+	if (!page)
+		return NULL;
+
+	return page_address(page);
+}
+
 static struct perf_mmap_data *
 perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
 {
@@ -2304,12 +2317,12 @@ perf_mmap_data_alloc(struct perf_event *event, int nr_pages)
 	if (!data)
 		goto fail;
 
-	data->user_page = (void *)get_zeroed_page(GFP_KERNEL);
+	data->user_page = perf_mmap_alloc_page(event->cpu);
 	if (!data->user_page)
 		goto fail_user_page;
 
 	for (i = 0; i < nr_pages; i++) {
-		data->data_pages[i] = (void *)get_zeroed_page(GFP_KERNEL);
+		data->data_pages[i] = perf_mmap_alloc_page(event->cpu);
 		if (!data->data_pages[i])
 			goto fail_data_pages;
 	}

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