[PATCH v3 03/23] perf: Support high-order allocations for AUX space

Alexander Shishkin
2014-08-11T05:26:57Z

Some pmus (such as BTS or Intel PT without multiple-entry ToPA capability)
don't support scatter-gather and will prefer larger contiguous areas for
their output regions.

This patch adds a new pmu capability to request higher order allocations.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
---
include/linux/perf_event.h | 1 +
kernel/events/ring_buffer.c | 51 +++++++++++++++++++++++++++++++++++++++------
2 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index cf62338421..4d9ede200f 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -170,6 +170,7 @@ struct perf_event;
* pmu::capabilities flags
*/
#define PERF_PMU_CAP_NO_INTERRUPT 0x01
+#define PERF_PMU_CAP_AUX_NO_SG 0x02

/**
* struct pmu - generic performance monitoring unit
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 00708d5916..d10919ca42 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -242,29 +242,68 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
spin_lock_init(&rb->event_lock);
}

+#define PERF_AUX_GFP (GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN | __GFP_NORETRY)
+
+static struct page *rb_alloc_aux_page(int node, int order)
+{
+ struct page *page;
+
+ if (order > MAX_ORDER)
+ order = MAX_ORDER;
+
+ do {
+ page = alloc_pages_node(node, PERF_AUX_GFP, order);
+ } while (!page && order--);
+
+ if (page && order) {
+ /*
+ * Communicate the allocation size to the driver
+ */
+ split_page(page, order);
+ SetPagePrivate(page);
+ set_page_private(page, order);
+ }
+
+ return page;
+}
+
+static void rb_free_aux_page(struct ring_buffer *rb, int idx)
+{
+ struct page *page = virt_to_page(rb->aux_pages[idx]);
+
+ ClearPagePrivate(page);
+ page->mapping = NULL;
+ __free_page(page);
+}
+
int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
pgoff_t pgoff, int nr_pages, int flags)
{
bool overwrite = !(flags & RING_BUFFER_WRITABLE);
int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu);
- int ret = -ENOMEM;
+ int ret = -ENOMEM, order = 0;

if (!has_aux(event))
return -ENOTSUPP;

+ if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG)
+ order = get_order(nr_pages * PAGE_SIZE);
+
rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node);
if (!rb->aux_pages)
return -ENOMEM;

- for (rb->aux_nr_pages = 0; rb->aux_nr_pages < nr_pages;
- rb->aux_nr_pages++) {
+ for (rb->aux_nr_pages = 0; rb->aux_nr_pages < nr_pages;) {
struct page *page;
+ int last;

- page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
+ page = rb_alloc_aux_page(node, order);
if (!page)
goto out;

- rb->aux_pages[rb->aux_nr_pages] = page_address(page);
+ for (last = rb->aux_nr_pages + (1 << page_private(page));
+ last > rb->aux_nr_pages; rb->aux_nr_pages++)
+ rb->aux_pages[rb->aux_nr_pages] = page_address(page++);
}

rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages,
@@ -298,7 +337,7 @@ void rb_free_aux(struct ring_buffer *rb, struct perf_event *event)
}

for (pg = 0; pg < rb->aux_nr_pages; pg++)
- free_page((unsigned long)rb->aux_pages[pg]);
+ rb_free_aux_page(rb, pg);

kfree(rb->aux_pages);
rb->aux_nr_pages = 0;
--
2.1.0.rc1