[PATCH net-next v1 10/11] xdp: add tracepoints for XDP mem

Jesper Dangaard Brouer
2019-06-13T18:28:58Z

These tracepoints make it easier to troubleshoot XDP mem id disconnect.

The xdp:mem_disconnect tracepoint cannot be replaced via kprobe. It is
placed at the last stable place for the pointer to struct xdp_mem_allocator,
just before it's scheduled for RCU removal. It also extract info on
'safe_to_remove' and 'force'.

Detailed info about in-flight pages is not available at this layer. The next
patch will added tracepoints needed at the page_pool layer for this.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
include/net/xdp_priv.h | 23 +++++++++
include/trace/events/xdp.h | 115 ++++++++++++++++++++++++++++++++++++++++++++
net/core/xdp.c | 21 ++------
3 files changed, 143 insertions(+), 16 deletions(-)
create mode 100644 include/net/xdp_priv.h

diff --git a/include/net/xdp_priv.h b/include/net/xdp_priv.h
new file mode 100644
index 000000000000..6a8cba6ea79a
--- /dev/null
+++ b/include/net/xdp_priv.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_NET_XDP_PRIV_H__
+#define __LINUX_NET_XDP_PRIV_H__
+
+#include <linux/rhashtable.h>
+
+/* Private to net/core/xdp.c, but used by trace/events/xdp.h */
+struct xdp_mem_allocator {
+ struct xdp_mem_info mem;
+ union {
+ void *allocator;
+ struct page_pool *page_pool;
+ struct zero_copy_allocator *zc_alloc;
+ };
+ int disconnect_cnt;
+ unsigned long defer_start;
+ struct rhash_head node;
+ struct rcu_head rcu;
+ struct delayed_work defer_wq;
+ unsigned long defer_warn;
+};
+
+#endif /* __LINUX_NET_XDP_PRIV_H__ */
diff --git a/include/trace/events/xdp.h b/include/trace/events/xdp.h
index e95cb86b65cf..bb5e380e2ef3 100644
--- a/include/trace/events/xdp.h
+++ b/include/trace/events/xdp.h
@@ -269,6 +269,121 @@ TRACE_EVENT(xdp_devmap_xmit,
__entry->from_ifindex, __entry->to_ifindex, __entry->err)
);

+/* Expect users already include <net/xdp.h>, but not xdp_priv.h */
+#include <net/xdp_priv.h>
+
+#define __MEM_TYPE_MAP(FN) \
+ FN(PAGE_SHARED) \
+ FN(PAGE_ORDER0) \
+ FN(PAGE_POOL) \
+ FN(ZERO_COPY)
+
+#define __MEM_TYPE_TP_FN(x) \
+ TRACE_DEFINE_ENUM(MEM_TYPE_##x);
+#define __MEM_TYPE_SYM_FN(x) \
+ { MEM_TYPE_##x, #x },
+#define __MEM_TYPE_SYM_TAB \
+ __MEM_TYPE_MAP(__MEM_TYPE_SYM_FN) { -1, 0 }
+__MEM_TYPE_MAP(__MEM_TYPE_TP_FN)
+
+TRACE_EVENT(mem_disconnect,
+
+ TP_PROTO(const struct xdp_mem_allocator *xa,
+ bool safe_to_remove, bool force),
+
+ TP_ARGS(xa, safe_to_remove, force),
+
+ TP_STRUCT__entry(
+ __field(const struct xdp_mem_allocator *, xa)
+ __field(u32, mem_id)
+ __field(u32, mem_type)
+ __field(const void *, allocator)
+ __field(bool, safe_to_remove)
+ __field(bool, force)
+ __field(int, disconnect_cnt)
+ ),
+
+ TP_fast_assign(
+ __entry->xa = xa;
+ __entry->mem_id = xa->mem.id;
+ __entry->mem_type = xa->mem.type;
+ __entry->allocator = xa->allocator;
+ __entry->safe_to_remove = safe_to_remove;
+ __entry->force = force;
+ __entry->disconnect_cnt = xa->disconnect_cnt;
+ ),
+
+ TP_printk("mem_id=%d mem_type=%s allocator=%p"
+ " safe_to_remove=%s force=%s disconnect_cnt=%d",
+ __entry->mem_id,
+ __print_symbolic(__entry->mem_type, __MEM_TYPE_SYM_TAB),
+ __entry->allocator,
+ __entry->safe_to_remove ? "true" : "false",
+ __entry->force ? "true" : "false",
+ __entry->disconnect_cnt
+ )
+);
+
+TRACE_EVENT(mem_connect,
+
+ TP_PROTO(const struct xdp_mem_allocator *xa,
+ const struct xdp_rxq_info *rxq),
+
+ TP_ARGS(xa, rxq),
+
+ TP_STRUCT__entry(
+ __field(const struct xdp_mem_allocator *, xa)
+ __field(u32, mem_id)
+ __field(u32, mem_type)
+ __field(const void *, allocator)
+ __field(const struct xdp_rxq_info *, rxq)
+ __field(int, ifindex)
+ ),
+
+ TP_fast_assign(
+ __entry->xa = xa;
+ __entry->mem_id = xa->mem.id;
+ __entry->mem_type = xa->mem.type;
+ __entry->allocator = xa->allocator;
+ __entry->rxq = rxq;
+ __entry->ifindex = rxq->dev->ifindex;
+ ),
+
+ TP_printk("mem_id=%d mem_type=%s allocator=%p"
+ " ifindex=%d",
+ __entry->mem_id,
+ __print_symbolic(__entry->mem_type, __MEM_TYPE_SYM_TAB),
+ __entry->allocator,
+ __entry->ifindex
+ )
+);
+
+TRACE_EVENT(mem_return_failed,
+
+ TP_PROTO(const struct xdp_mem_info *mem,
+ const struct page *page),
+
+ TP_ARGS(mem, page),
+
+ TP_STRUCT__entry(
+ __field(const struct page *, page)
+ __field(u32, mem_id)
+ __field(u32, mem_type)
+ ),
+
+ TP_fast_assign(
+ __entry->page = page;
+ __entry->mem_id = mem->id;
+ __entry->mem_type = mem->type;
+ ),
+
+ TP_printk("mem_id=%d mem_type=%s page=%p",
+ __entry->mem_id,
+ __print_symbolic(__entry->mem_type, __MEM_TYPE_SYM_TAB),
+ __entry->page
+ )
+);
+
#endif /* _TRACE_XDP_H */

#include <trace/define_trace.h>
diff --git a/net/core/xdp.c b/net/core/xdp.c
index 53bce4fa776a..4ad9e48b76a8 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -14,6 +14,8 @@
#include <net/page_pool.h>

#include <net/xdp.h>
+#include <net/xdp_priv.h> /* struct xdp_mem_allocator */
+#include <trace/events/xdp.h>

#define REG_STATE_NEW 0x0
#define REG_STATE_REGISTERED 0x1
@@ -29,21 +31,6 @@ static int mem_id_next = MEM_ID_MIN;
static bool mem_id_init; /* false */
static struct rhashtable *mem_id_ht;

-struct xdp_mem_allocator {
- struct xdp_mem_info mem;
- union {
- void *allocator;
- struct page_pool *page_pool;
- struct zero_copy_allocator *zc_alloc;
- };
- struct rhash_head node;
- struct rcu_head rcu;
- struct delayed_work defer_wq;
- unsigned long defer_start;
- unsigned long defer_warn;
- int disconnect_cnt;
-};
-
static u32 xdp_mem_id_hashfn(const void *data, u32 len, u32 seed)
{
const u32 *k = data;
@@ -117,7 +104,7 @@ bool __mem_id_disconnect(int id, bool force)
if (xa->mem.type == MEM_TYPE_PAGE_POOL)
safe_to_remove = page_pool_request_shutdown(xa->page_pool);

- /* TODO: Tracepoint will be added here in next-patch */
+ trace_mem_disconnect(xa, safe_to_remove, force);

if ((safe_to_remove || force) &&
!rhashtable_remove_fast(mem_id_ht, &xa->node, mem_id_rht_params))
@@ -385,6 +372,7 @@ int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,

mutex_unlock(&mem_id_lock);

+ trace_mem_connect(xdp_alloc, xdp_rxq);
return 0;
err:
mutex_unlock(&mem_id_lock);
@@ -417,6 +405,7 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
} else {
/* Hopefully stack show who to blame for late return */
WARN_ONCE(1, "page_pool gone mem.id=%d", mem->id);
+ trace_mem_return_failed(mem, page);
put_page(page);
}
rcu_read_unlock();