[dpdk-dev] [PATCH v4 2/2] vhost: binary search address mapping table

[Marvin Liu <yong.liu@intel.com>]

If Tx zero copy enabled, gpa to hpa mapping table is updated one by
one. This will harm performance when guest memory backend using 2M
hugepages. Now utilize binary search to find the entry in mapping
table, meanwhile set the threshold to 256 entries for linear search.

Signed-off-by: Marvin Liu <yong.liu@intel.com>

diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
index 507dbf214..998e133ad 100644
--- a/lib/librte_vhost/vhost.h
+++ b/lib/librte_vhost/vhost.h
@@ -546,20 +546,48 @@ extern int vhost_data_log_level;
 #define MAX_VHOST_DEVICE	1024
 extern struct virtio_net *vhost_devices[MAX_VHOST_DEVICE];
 
+#define VHOST_BINARY_SEARCH_THRESH 256
+
+static __rte_always_inline int guest_page_addrcmp(const void *p1,
+						const void *p2)
+{
+	const struct guest_page *page1 = (const struct guest_page *)p1;
+	const struct guest_page *page2 = (const struct guest_page *)p2;
+
+	if (page1->guest_phys_addr > page2->guest_phys_addr)
+		return 1;
+	if (page1->guest_phys_addr < page2->guest_phys_addr)
+		return -1;
+
+	return 0;
+}
+
 /* Convert guest physical address to host physical address */
 static __rte_always_inline rte_iova_t
 gpa_to_hpa(struct virtio_net *dev, uint64_t gpa, uint64_t size)
 {
 	uint32_t i;
 	struct guest_page *page;
-
-	for (i = 0; i < dev->nr_guest_pages; i++) {
-		page = &dev->guest_pages[i];
-
-		if (gpa >= page->guest_phys_addr &&
-		    gpa + size < page->guest_phys_addr + page->size) {
-			return gpa - page->guest_phys_addr +
-			       page->host_phys_addr;
+	struct guest_page key;
+
+	if (dev->nr_guest_pages >= VHOST_BINARY_SEARCH_THRESH) {
+		key.guest_phys_addr = gpa;
+		page = bsearch(&key, dev->guest_pages, dev->nr_guest_pages,
+			       sizeof(struct guest_page), guest_page_addrcmp);
+		if (page) {
+			if (gpa + size < page->guest_phys_addr + page->size)
+				return gpa - page->guest_phys_addr +
+					page->host_phys_addr;
+		}
+	} else {
+		for (i = 0; i < dev->nr_guest_pages; i++) {
+			page = &dev->guest_pages[i];
+
+			if (gpa >= page->guest_phys_addr &&
+			    gpa + size < page->guest_phys_addr +
+			    page->size)
+				return gpa - page->guest_phys_addr +
+				       page->host_phys_addr;
 		}
 	}
 
diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
index 79fcb9d19..15e50d27d 100644
--- a/lib/librte_vhost/vhost_user.c
+++ b/lib/librte_vhost/vhost_user.c
@@ -965,6 +965,12 @@ add_guest_pages(struct virtio_net *dev, struct rte_vhost_mem_region *reg,
 		reg_size -= size;
 	}
 
+	/* sort guest page array if over binary search threshold */
+	if (dev->nr_guest_pages >= VHOST_BINARY_SEARCH_THRESH) {
+		qsort((void *)dev->guest_pages, dev->nr_guest_pages,
+			sizeof(struct guest_page), guest_page_addrcmp);
+	}
+
 	return 0;
 }
 
-- 
2.17.1