From dda10fc801a9d81829e624ef75ecdfc94f39b310 Mon Sep 17 00:00:00 2001 From: Nick Child Date: Wed, 7 Aug 2024 16:18:03 -0500 Subject: [PATCH] ibmvnic: Only replenish rx pool when resources are getting low Previously, the driver would replenish the rx pool if the polling function consumed less than the budget. The logic being that the driver did not exhaust its budget so that must mean that the driver is not busy and has cycles to spare for replenishing the pool. So pool replenishment happens on every poll which did not consume the budget. This can very costly during request-response tests. In fact, an extra ~100pps can be seen in TCP_RR_150 tests when we remove this conditional. Trace results (ftrace, graph-time=1) for the poll function are below: Previous results: ibmvnic_poll = 64951846.0 us / 4167628.0 hits = AVG 15.58 replenish_rx_pool = 17602846.0 us / 4710437.0 hits = AVG 3.74 Now: ibmvnic_poll = 57673941.0 us / 4791737.0 hits = AVG 12.04 replenish_rx_pool = 3938171.6 us / 4314.0 hits = AVG 912.88 While the replenish function takes longer, it is hit less frequently meaning the ibmvnic_poll function, on average, is faster. Furthermore, this change does not have a negative effect on performance bandwidth/latency measurements. Signed-off-by: Nick Child Link: https://patch.msgid.link/20240807211809.1259563-2-nnac123@linux.ibm.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/ibm/ibmvnic.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c index 23ebeb143987f..857d585bd2297 100644 --- a/drivers/net/ethernet/ibm/ibmvnic.c +++ b/drivers/net/ethernet/ibm/ibmvnic.c @@ -3527,9 +3527,8 @@ static int ibmvnic_poll(struct napi_struct *napi, int budget) } if (adapter->state != VNIC_CLOSING && - ((atomic_read(&adapter->rx_pool[scrq_num].available) < - adapter->req_rx_add_entries_per_subcrq / 2) || - frames_processed < budget)) + (atomic_read(&adapter->rx_pool[scrq_num].available) < + adapter->req_rx_add_entries_per_subcrq / 2)) replenish_rx_pool(adapter, &adapter->rx_pool[scrq_num]); if (frames_processed < budget) { if (napi_complete_done(napi, frames_processed)) {