From 2543a6000e593a213fba5b504f52c07e09f39835 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 24 Nov 2020 12:38:22 -0800 Subject: [PATCH] gro_cells: reduce number of synchronize_net() calls After cited commit, gro_cells_destroy() became damn slow on hosts with a lot of cores. This is because we have one additional synchronize_net() per cpu as stated in the changelog. gro_cells_init() is setting NAPI_STATE_NO_BUSY_POLL, and this was enough to not have one synchronize_net() call per netif_napi_del() We can factorize all the synchronize_net() to a single one, right before freeing per-cpu memory. Fixes: 5198d545dba8 ("net: remove napi_hash_del() from driver-facing API") Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/r/20201124203822.1360107-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski --- net/core/gro_cells.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/core/gro_cells.c b/net/core/gro_cells.c index e095fb871d91..6eb2e5ec2c50 100644 --- a/net/core/gro_cells.c +++ b/net/core/gro_cells.c @@ -99,9 +99,14 @@ void gro_cells_destroy(struct gro_cells *gcells) struct gro_cell *cell = per_cpu_ptr(gcells->cells, i); napi_disable(&cell->napi); - netif_napi_del(&cell->napi); + __netif_napi_del(&cell->napi); __skb_queue_purge(&cell->napi_skbs); } + /* This barrier is needed because netpoll could access dev->napi_list + * under rcu protection. + */ + synchronize_net(); + free_percpu(gcells->cells); gcells->cells = NULL; } -- 2.11.0