On 07/09/2021 14.35, Lorenzo Bianconi wrote:
Introduce xdp_update_skb_shared_info routine to update frags array
metadata in skb_shared_info data structure converting to a skb from
a xdp_buff or xdp_frame.
According to the current skb_shared_info architecture in
xdp_frame/xdp_buff and to the xdp multi-buff support, there is
no need to run skb_add_rx_frag() and reset frags array converting the buffer
to a skb since the frag array will be in the same position for xdp_buff/xdp_frame
and for the skb, we just need to update memory metadata.
Introduce XDP_FLAGS_PF_MEMALLOC flag in xdp_buff_flags in order to mark
the xdp_buff or xdp_frame as under memory-pressure if pages of the frags array
are under memory pressure. Doing so we can avoid looping over all fragments in
xdp_update_skb_shared_info routine. The driver is expected to set the
flag constructing the xdp_buffer using xdp_buff_set_frag_pfmemalloc
utility routine.
Rely on xdp_update_skb_shared_info in __xdp_build_skb_from_frame routine
converting the multi-buff xdp_frame to a skb after performing a XDP_REDIRECT.
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Signed-off-by: Lorenzo Bianconi <lorenzo@xxxxxxxxxx>
---
include/net/xdp.h | 33 ++++++++++++++++++++++++++++++++-
net/core/xdp.c | 17 +++++++++++++++++
2 files changed, 49 insertions(+), 1 deletion(-)
diff --git a/include/net/xdp.h b/include/net/xdp.h
index ed5ea784fd45..53cccdc9528c 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -67,7 +67,10 @@ struct xdp_txq_info {
};
enum xdp_buff_flags {
- XDP_FLAGS_MULTI_BUFF = BIT(0), /* non-linear xdp buff */
+ XDP_FLAGS_MULTI_BUFF = BIT(0), /* non-linear xdp buff */
+ XDP_FLAGS_FRAGS_PF_MEMALLOC = BIT(1), /* xdp multi-buff paged memory
+ * is under pressure
+ */
};
struct xdp_buff {
@@ -96,6 +99,16 @@ static __always_inline void xdp_buff_clear_mb(struct xdp_buff *xdp)
xdp->flags &= ~XDP_FLAGS_MULTI_BUFF;
}
+static __always_inline bool xdp_buff_is_frag_pfmemalloc(struct xdp_buff *xdp)
+{
+ return !!(xdp->flags & XDP_FLAGS_FRAGS_PF_MEMALLOC);
+}
+
+static __always_inline void xdp_buff_set_frag_pfmemalloc(struct xdp_buff *xdp)
+{
+ xdp->flags |= XDP_FLAGS_FRAGS_PF_MEMALLOC;
+}
+
static __always_inline void
xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq)
{
@@ -151,6 +164,11 @@ static __always_inline bool xdp_frame_is_mb(struct xdp_frame *frame)
return !!(frame->flags & XDP_FLAGS_MULTI_BUFF);
}
+static __always_inline bool xdp_frame_is_frag_pfmemalloc(struct xdp_frame *frame)
+{
+ return !!(frame->flags & XDP_FLAGS_FRAGS_PF_MEMALLOC);
+}
+
#define XDP_BULK_QUEUE_SIZE 16
struct xdp_frame_bulk {
int count;
@@ -186,6 +204,19 @@ static inline void xdp_scrub_frame(struct xdp_frame *frame)
frame->dev_rx = NULL;
}
+static inline void
+xdp_update_skb_shared_info(struct sk_buff *skb, u8 nr_frags,
+ unsigned int size, unsigned int truesize,
+ bool pfmemalloc)
+{
+ skb_shinfo(skb)->nr_frags = nr_frags;
+
+ skb->len += size;
+ skb->data_len += size;
+ skb->truesize += truesize;
+ skb->pfmemalloc |= pfmemalloc;
Do we need to clear gso_type here as it is shared/union with
xdp_frags_size ?
(see below ... it is already cleared before call)
+}
+
/* Avoids inlining WARN macro in fast-path */
void xdp_warn(const char *msg, const char *func, const int line);
#define XDP_WARN(msg) xdp_warn(msg, __func__, __LINE__)
diff --git a/net/core/xdp.c b/net/core/xdp.c
index cc92ccb38432..504be3ce3ca9 100644
--- a/net/core/xdp.c
+++ b/net/core/xdp.c
@@ -531,8 +531,20 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
struct sk_buff *skb,
struct net_device *dev)
{
+ unsigned int frag_size, frag_tsize;
unsigned int headroom, frame_size;
void *hard_start;
+ u8 nr_frags;
+
+ /* xdp multi-buff frame */
+ if (unlikely(xdp_frame_is_mb(xdpf))) {
+ struct skb_shared_info *sinfo;
+
+ sinfo = xdp_get_shared_info_from_frame(xdpf);
+ frag_tsize = sinfo->xdp_frags_tsize;
+ frag_size = sinfo->xdp_frags_size;
+ nr_frags = sinfo->nr_frags;
+ }
/* Part of headroom was reserved to xdpf */
headroom = sizeof(*xdpf) + xdpf->headroom;
@@ -552,6 +564,11 @@ struct sk_buff *__xdp_build_skb_from_frame(struct xdp_frame *xdpf,
if (xdpf->metasize)
skb_metadata_set(skb, xdpf->metasize);
+ if (unlikely(xdp_frame_is_mb(xdpf)))
+ xdp_update_skb_shared_info(skb, nr_frags,
+ frag_size, frag_tsize,
+ xdp_frame_is_frag_pfmemalloc(xdpf));
+
There is a build_skb_around() call before this call, which via
__build_skb_around() will clear top part of skb_shared_info.
(Thus, clearing gso_type not needed ... see above)
/* Essential SKB info: protocol and skb->dev */
skb->protocol = eth_type_trans(skb, dev);
Acked-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
