Re: [PATCH net-next 5/6] xsk: Change the default frame size to 4096 and allow controlling it

Björn Töpel Fri, 26 Apr 2019 13:27:32 -0700

On 2019-04-26 13:42, Maxim Mikityanskiy wrote:

The typical XDP memory scheme is one packet per page. Change the AF_XDP
frame size in libbpf to 4096, which is the page size on x86, to allow
libbpf to be used with the drivers with the packet-per-page scheme.


Add a command line option -f to xdpsock to allow to specify a custom
frame size.


I'd prefer size, in favor of "frame shift".


Björn

Signed-off-by: Maxim Mikityanskiy <maxi...@mellanox.com>
---
  samples/bpf/xdpsock_user.c | 39 +++++++++++++++++++++++++-------------
  tools/lib/bpf/xsk.h        |  2 +-
  2 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index a6b13025ee79..3746f699cf2f 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -69,6 +69,7 @@ static int opt_queue;
  static int opt_poll;
  static int opt_interval = 1;
  static u32 opt_xdp_bind_flags;
+static int opt_xsk_frame_shift = XSK_UMEM__DEFAULT_FRAME_SHIFT;
  static __u32 prog_id;

struct xsk_umem_info {

@@ -93,6 +94,11 @@ struct xsk_socket_info {
  static int num_socks;
  struct xsk_socket_info *xsks[MAX_SOCKS];

+static inline int get_buf_size(int frames)

+{
+       return frames << opt_xsk_frame_shift;
+}
+
  static unsigned long get_nsecs(void)
  {
        struct timespec ts;
@@ -277,6 +283,12 @@ static size_t gen_eth_frame(struct xsk_umem_info *umem, 
u64 addr)
  static struct xsk_umem_info *xsk_configure_umem(void *buffer, u64 size)
  {
        struct xsk_umem_info *umem;
+       struct xsk_umem_config cfg = {
+               .fill_size = XSK_RING_PROD__DEFAULT_NUM_DESCS,
+               .comp_size = XSK_RING_CONS__DEFAULT_NUM_DESCS,
+               .frame_size = get_buf_size(1),
+               .frame_headroom = XSK_UMEM__DEFAULT_FRAME_HEADROOM,
+       };
        int ret;

umem = calloc(1, sizeof(*umem));

@@ -284,7 +296,7 @@ static struct xsk_umem_info *xsk_configure_umem(void 
*buffer, u64 size)
                exit_with_error(errno);

ret = xsk_umem__create(&umem->umem, buffer, size, &umem->fq, &umem->cq,

-                              NULL);
+                              &cfg);
        if (ret)
                exit_with_error(-ret);

@@ -325,9 +337,8 @@ static struct xsk_socket_info *xsk_configure_socket(struct xsk_umem_info *umem)

        if (ret != XSK_RING_PROD__DEFAULT_NUM_DESCS)
                exit_with_error(-ret);
        for (i = 0;
-            i < XSK_RING_PROD__DEFAULT_NUM_DESCS *
-                    XSK_UMEM__DEFAULT_FRAME_SIZE;
-            i += XSK_UMEM__DEFAULT_FRAME_SIZE)
+            i < get_buf_size(XSK_RING_PROD__DEFAULT_NUM_DESCS);
+            i += get_buf_size(1))
                *xsk_ring_prod__fill_addr(&xsk->umem->fq, idx++) = i;
        xsk_ring_prod__submit(&xsk->umem->fq,
                              XSK_RING_PROD__DEFAULT_NUM_DESCS);
@@ -348,6 +359,7 @@ static struct option long_options[] = {
        {"zero-copy", no_argument, 0, 'z'},
        {"copy", no_argument, 0, 'c'},
        {"combined", no_argument, 0, 'C'},
+       {"frame-shift", required_argument, 0, 'f'},
        {0, 0, 0, 0}
  };

@@ -368,8 +380,9 @@ static void usage(const char *prog)

                "  -z, --zero-copy      Force zero-copy mode.\n"
                "  -c, --copy           Force copy mode.\n"
                "  -C, --combined       Driver supports combined XSK and non-XSK 
traffic in a channel.\n"
+               "  -f, --frame-shift=n  Set the frame shift (default is %d, frame size is 
1 << frame-shift).\n"
                "\n";
-       fprintf(stderr, str, prog);
+       fprintf(stderr, str, prog, XSK_UMEM__DEFAULT_FRAME_SHIFT);
        exit(EXIT_FAILURE);
  }

@@ -380,7 +393,7 @@ static void parse_command_line(int argc, char **argv)

        opterr = 0;

for (;;) {

-               c = getopt_long(argc, argv, "Frtli:q:psSNn:czC", long_options,
+               c = getopt_long(argc, argv, "Frtli:q:psSNn:czCf:", long_options,
                                &option_index);
                if (c == -1)
                        break;
@@ -426,6 +439,9 @@ static void parse_command_line(int argc, char **argv)
                case 'C':
                        opt_libbpf_flags |= XSK_LIBBPF_FLAGS__COMBINED_CHANNELS;
                        break;
+               case 'f':
+                       opt_xsk_frame_shift = atoi(optarg);
+                       break;
                default:
                        usage(basename(argv[0]));
                }
@@ -589,8 +605,7 @@ static void tx_only(struct xsk_socket_info *xsk)

for (i = 0; i < BATCH_SIZE; i++) {

                                xsk_ring_prod__tx_desc(&xsk->tx, idx + i)->addr
-                                       = (frame_nb + i) <<
-                                       XSK_UMEM__DEFAULT_FRAME_SHIFT;
+                                       = get_buf_size(frame_nb + i);
                                xsk_ring_prod__tx_desc(&xsk->tx, idx + i)->len =
                                        sizeof(pkt_data) - 1;
                        }
@@ -667,20 +682,18 @@ int main(int argc, char **argv)
        }

ret = posix_memalign(&bufs, getpagesize(), /* PAGE_SIZE aligned */

-                            NUM_FRAMES * XSK_UMEM__DEFAULT_FRAME_SIZE);
+                            get_buf_size(NUM_FRAMES));
        if (ret)
                exit_with_error(ret);

/* Create sockets... */

-       umem = xsk_configure_umem(bufs,
-                                 NUM_FRAMES * XSK_UMEM__DEFAULT_FRAME_SIZE);
+       umem = xsk_configure_umem(bufs, get_buf_size(NUM_FRAMES));
        xsks[num_socks++] = xsk_configure_socket(umem);

if (opt_bench == BENCH_TXONLY) {

                int i;

- for (i = 0; i < NUM_FRAMES * XSK_UMEM__DEFAULT_FRAME_SIZE;

-                    i += XSK_UMEM__DEFAULT_FRAME_SIZE)
+               for (i = 0; i < get_buf_size(NUM_FRAMES); i += get_buf_size(1))
                        (void)gen_eth_frame(umem, i);
        }

diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h

index 72a49b102ab3..946245a7272e 100644
--- a/tools/lib/bpf/xsk.h
+++ b/tools/lib/bpf/xsk.h
@@ -157,7 +157,7 @@ LIBBPF_API int xsk_socket__fd(const struct xsk_socket *xsk);

#define XSK_RING_CONS__DEFAULT_NUM_DESCS 2048

  #define XSK_RING_PROD__DEFAULT_NUM_DESCS      2048
-#define XSK_UMEM__DEFAULT_FRAME_SHIFT    11 /* 2048 bytes */
+#define XSK_UMEM__DEFAULT_FRAME_SHIFT    12 /* 4096 bytes */
  #define XSK_UMEM__DEFAULT_FRAME_SIZE     (1 << XSK_UMEM__DEFAULT_FRAME_SHIFT)
  #define XSK_UMEM__DEFAULT_FRAME_HEADROOM 0

Re: [PATCH net-next 5/6] xsk: Change the default frame size to 4096 and allow controlling it

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