perf: Support high-order allocations for AUX space

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kaixu Xia <kaixu.xia@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Robert Richter <rric@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Cc: kan.liang@intel.com
Cc: markus.t.metzger@intel.com
Cc: mathieu.poirier@linaro.org
Link: http://lkml.kernel.org/r/1421237903-181015-4-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 50 insertions, 6 deletions

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 3de9c4e9ea9f..ed0859e33b2f 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -243,30 +243,74 @@ 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, max_order = 0;
 
         if (!has_aux(event))
                 return -ENOTSUPP;
 
+        if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG)
+                /*
+                 * We need to start with the max_order that fits in nr_pages,
+                 * not the other way around, hence ilog2() and not get_order.
+                 */
+                max_order = ilog2(nr_pages);
+
         rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node);
         if (!rb->aux_pages)
                 return -ENOMEM;
 
         rb->free_aux = event->pmu->free_aux;
-        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, order;
 
-                page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
+                order = min(max_order, ilog2(nr_pages - rb->aux_nr_pages));
+                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,
@@ -304,7 +348,7 @@ static void __rb_free_aux(struct ring_buffer *rb)
         }
 
         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;