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Tariq Toukan authored
When many packets reside on the same page, the bulking of page_ref modifications reduces the total number of atomic operations executed. Besides the necessary 2 operations on page alloc/free, we have the following extra ops per page: - one on WQE allocation (bump refcnt to maximum possible), - zero ops for SKBs, - one on WQE free, a constant of two operations in total, no matter how many packets/SKBs actually populate the page. Without this bulking, we have: - no ops on WQE allocation or free, - one op per SKB, Comparing the two methods when PAGE_SIZE is 4K: - As mentioned above, bulking method always executes 2 operations, not more, but not less. - In the default MTU configuration (1500, stride size is 2K), the non-bulking method execute 2 ops as well. - For larger MTUs with stride size of 4K, non-bulking method executes only a single op. - For XDP (stride size of 4K, no SKBs), non-bulking method executes no ops at all! Hence, to optimize the flows with linear SKB and XDP over Striding RQ, we here remove the page_ref bulking method. Performance testing: ConnectX-5, Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz. Single core packet rate (64 bytes). Early drop in TC: no degradation. XDP_DROP: before: 14,270,188 pps after: 20,503,603 pps, 43% improvement. Signed-off-by:
Tariq Toukan <tariqt@mellanox.com> Signed-off-by:
Saeed Mahameed <saeedm@mellanox.com>
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