On 4 Jun 2019, at 8:04, Maciej Fijalkowski wrote:
On Tue, 4 Jun 2019 10:06:36 +0200
Björn Töpel <bjorn.topel@xxxxxxxxx> wrote:
On 2019-06-03 15:19, Maciej Fijalkowski wrote:
Let's get into the driver via ndo_bpf with command set to
XDP_SETUP_UMEM
with fill queue that already contains some available entries that
can be
used by Rx driver rings. Things worked in such way on old version of
xdpsock (that lacked libbpf support) and there's no particular
reason
for having this preparation done after bind().
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
Signed-off-by: Krzysztof Kazimierczak
<krzysztof.kazimierczak@xxxxxxxxx>
---
samples/bpf/xdpsock_user.c | 15 ---------------
tools/lib/bpf/xsk.c | 19 ++++++++++++++++++-
2 files changed, 18 insertions(+), 16 deletions(-)
diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index d08ee1ab7bb4..e9dceb09b6d1 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -296,8 +296,6 @@ static struct xsk_socket_info
*xsk_configure_socket(struct xsk_umem_info *umem)
struct xsk_socket_config cfg;
struct xsk_socket_info *xsk;
int ret;
- u32 idx;
- int i;
xsk = calloc(1, sizeof(*xsk));
if (!xsk)
@@ -318,19 +316,6 @@ static struct xsk_socket_info
*xsk_configure_socket(struct xsk_umem_info *umem)
if (ret)
exit_with_error(-ret);
- ret = xsk_ring_prod__reserve(&xsk->umem->fq,
- XSK_RING_PROD__DEFAULT_NUM_DESCS,
- &idx);
- 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)
- *xsk_ring_prod__fill_addr(&xsk->umem->fq, idx++) = i;
- xsk_ring_prod__submit(&xsk->umem->fq,
- XSK_RING_PROD__DEFAULT_NUM_DESCS);
-
return xsk;
}
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index 38667b62f1fe..57dda1389870 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -529,7 +529,8 @@ int xsk_socket__create(struct xsk_socket
**xsk_ptr, const char *ifname,
struct xdp_mmap_offsets off;
struct xsk_socket *xsk;
socklen_t optlen;
- int err;
+ int err, i;
+ u32 idx;
if (!umem || !xsk_ptr || !rx || !tx)
return -EFAULT;
@@ -632,6 +633,22 @@ int xsk_socket__create(struct xsk_socket
**xsk_ptr, const char *ifname,
}
xsk->tx = tx;
+ err = xsk_ring_prod__reserve(umem->fill,
+ XSK_RING_PROD__DEFAULT_NUM_DESCS,
+ &idx);
+ if (err != XSK_RING_PROD__DEFAULT_NUM_DESCS) {
+ err = -errno;
+ goto out_mmap_tx;
+ }
+
+ for (i = 0;
+ i < XSK_RING_PROD__DEFAULT_NUM_DESCS *
+ XSK_UMEM__DEFAULT_FRAME_SIZE;
+ i += XSK_UMEM__DEFAULT_FRAME_SIZE)
+ *xsk_ring_prod__fill_addr(umem->fill, idx++) = i;
+ xsk_ring_prod__submit(umem->fill,
+ XSK_RING_PROD__DEFAULT_NUM_DESCS);
+
Here, entries are added to the umem fill ring regardless if Rx is
being
used or not. For a Tx only setup, this is not what we want, right?
Right, but we have such behavior even without this patch. So I see two
options
here:
- if you agree with this patch, then I guess we would need to pass the
info to
libbpf what exactly we are setting up (txonly, rxdrop, l2fwd)?
- otherwise, we should be passing the opt_bench onto
xsk_configure_socket and
based on that decide whether we fill the fq or not?
Thinking out loud here; Now libbpf is making the decision which umem
entries that are added to the fill ring. The sample application has
this
(naive) scheme. I'm not sure that all applications would like that
policy. What do you think?
I find it convenient to have the fill queue in "initialized" state if
I am
making use of it, especially in case when I am doing the ZC so I must
give the
buffers to the driver via fill queue. So why would we bother other
applications
to provide it? I must admit that I haven't used AF_XDP with other apps
than the
example one, so I might not be able to elaborate further. Maybe other
people
have different feelings about it.
I use the library for setting up all the ring bookkeeping, but use my
own
application (and xdp program). So I'd prefer not having the library do
this -
as Björn notes, for some cases, the fill ring may not be populated. I
also
have some other use cases where I may not want to populate the fill ring
until
later.
While convenient, I think there's a limit to what the library should be
doing
for the user.
--
Jonathan
