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2094200b5f
This patch enables batched RX buffer replenishment in ibmveth by using the new firmware-supported h_add_logical_lan_buffers() hcall to submit up to 8 RX buffers in a single call, instead of repeatedly calling the single-buffer h_add_logical_lan_buffer() hcall. During the probe, with the patch, the driver queries ILLAN attributes to detect IBMVETH_ILLAN_RX_MULTI_BUFF_SUPPORT bit. If the attribute is present, rx_buffers_per_hcall is set to 8, enabling batched replenishment. Otherwise, it defaults to 1, preserving the original upstream behavior with no change in code flow for unsupported systems. The core rx replenish logic remains the same. But when batching is enabled, the driver aggregates up to 8 fully prepared descriptors into a single h_add_logical_lan_buffers() hypercall. If any allocation or DMA mapping fails while preparing a batch, only the successfully prepared buffers are submitted, and the remaining are deferred for the next replenish cycle. If at runtime the firmware stops accepting the batched hcall—e,g, after a Live Partition Migration (LPM) to a host that does not support h_add_logical_lan_buffers(), the hypercall returns H_FUNCTION. In that case, the driver transparently disables batching, resets rx_buffers_per_hcall to 1, and falls back to the single-buffer hcall in next future replenishments to take care of these and future buffers. Test were done on systems with firmware that both supports and does not support the new h_add_logical_lan_buffers hcall. On supported firmware, this reduces hypercall overhead significantly over multiple buffers. SAR measurements showed about a 15% improvement in packet processing rate under moderate RX load, with heavier traffic seeing gains more than 30% Signed-off-by: Mingming Cao <mmc@linux.ibm.com> Reviewed-by: Brian King <bjking1@linux.ibm.com> Reviewed-by: Haren Myneni <haren@linux.ibm.com> Reviewed-by: Dave Marquardt <davemarq@linux.ibm.com> Reviewed-by: Simon Horman <horms@kernel.org> Link: https://patch.msgid.link/20250719091356.57252-1-mmc@linux.ibm.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> |
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