On Thu, Jun 19, 2025 at 9:53 PM Willem de Bruijn <willemdebruijn.kernel@xxxxxxxxx> wrote: > > Jason Xing wrote: > > From: Jason Xing <kernelxing@xxxxxxxxxxx> > > > > The patch does the following things: > > - Add XDP_MAX_TX_BUDGET socket option. > > - Unify TX_BATCH_SIZE and MAX_PER_SOCKET_BUDGET into single one > > tx_budget_spent. > > - tx_budget_spent is set to 32 by default in the initialization phase. > > It's a per-socket granular control. > > > > The idea behind this comes out of real workloads in production. We use a > > user-level stack with xsk support to accelerate sending packets and > > minimize triggering syscall. When the packets are aggregated, it's not > > hard to hit the upper bound (namely, 32). The moment user-space stack > > fetches the -EAGAIN error number passed from sendto(), it will loop to try > > again until all the expected descs from tx ring are sent out to the driver. > > Enlarging the XDP_MAX_TX_BUDGET value contributes to less frequencies of > > sendto(). Besides, applications leveraging this setsockopt can adjust > > its proper value in time after noticing the upper bound issue happening. > > > > Signed-off-by: Jason Xing <kernelxing@xxxxxxxxxxx> > > --- > > V3 > > Link: https://lore.kernel.org/all/20250618065553.96822-1-kerneljasonxing@xxxxxxxxx/ > > 1. use a per-socket control (suggested by Stanislav) > > 2. unify both definitions into one > > 3. support setsockopt and getsockopt > > 4. add more description in commit message > > +1 on an XSK setsockopt only May I ask why only setsockopt? In tradition, dev_tx_weight can be read and written through running sysctl. I think they are the same? > > > > > V2 > > Link: https://lore.kernel.org/all/20250617002236.30557-1-kerneljasonxing@xxxxxxxxx/ > > 1. use a per-netns sysctl knob > > 2. use sysctl_xsk_max_tx_budget to unify both definitions. > > --- > > include/net/xdp_sock.h | 3 ++- > > include/uapi/linux/if_xdp.h | 1 + > > net/xdp/xsk.c | 36 +++++++++++++++++++++++++------ > > tools/include/uapi/linux/if_xdp.h | 1 + > > 4 files changed, 34 insertions(+), 7 deletions(-) > > > > diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h > > index e8bd6ddb7b12..8eecafad92c0 100644 > > --- a/include/net/xdp_sock.h > > +++ b/include/net/xdp_sock.h > > @@ -65,11 +65,12 @@ struct xdp_sock { > > struct xsk_queue *tx ____cacheline_aligned_in_smp; > > struct list_head tx_list; > > /* record the number of tx descriptors sent by this xsk and > > - * when it exceeds MAX_PER_SOCKET_BUDGET, an opportunity needs > > + * when it exceeds max_tx_budget, an opportunity needs > > * to be given to other xsks for sending tx descriptors, thereby > > * preventing other XSKs from being starved. > > */ > > u32 tx_budget_spent; > > + u32 max_tx_budget; > > This probably does not need to be a u32?
