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Jesper Dangaard Brouer authored
The check in pool_page_reusable (page_to_nid(page) == pool->p.nid) is not valid if page_pool was configured with pool->p.nid = NUMA_NO_NODE. The goal of the NUMA changes in commit d5394610 ("page_pool: Don't recycle non-reusable pages"), were to have RX-pages that belongs to the same NUMA node as the CPU processing RX-packet during softirq/NAPI. As illustrated by the performance measurements. This patch moves the NAPI checks out of fast-path, and at the same time solves the NUMA_NO_NODE issue. First realize that alloc_pages_node() with pool->p.nid = NUMA_NO_NODE will lookup current CPU nid (Numa ID) via numa_mem_id(), which is used as the the preferred nid. It is only in rare situations, where e.g. NUMA zone runs dry, that page gets doesn't get allocated from preferred nid. The page_pool API allows drivers to control the nid themselves via controlling pool->p.nid. This patch moves the NAPI check to when alloc cache is refilled, via dequeuing/consuming pages from the ptr_ring. Thus, we can allow placing pages from remote NUMA into the ptr_ring, as the dequeue/consume step will check the NUMA node. All current drivers using page_pool will alloc/refill RX-ring from same CPU running softirq/NAPI process. Drivers that control the nid explicitly, also use page_pool_update_nid when changing nid runtime. To speed up transision to new nid the alloc cache is now flushed on nid changes. This force pages to come from ptr_ring, which does the appropate nid check. For the NUMA_NO_NODE case, when a NIC IRQ is moved to another NUMA node, we accept that transitioning the alloc cache doesn't happen immediately. The preferred nid change runtime via consulting numa_mem_id() based on the CPU processing RX-packets. Notice, to avoid stressing the page buddy allocator and avoid doing too much work under softirq with preempt disabled, the NUMA check at ptr_ring dequeue will break the refill cycle, when detecting a NUMA mismatch. This will cause a slower transition, but its done on purpose. Fixes: d5394610 ("page_pool: Don't recycle non-reusable pages") Reported-by:
Li RongQing <lirongqing@baidu.com> Reported-by:
Yunsheng Lin <linyunsheng@huawei.com> Signed-off-by:
Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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