From 61bf0009a7657d394d942c8ee961b9ea5f2168fe Mon Sep 17 00:00:00 2001 From: Caleb Sander Mateos Date: Wed, 30 Oct 2024 18:23:26 -0600 Subject: dim: pass dim_sample to net_dim() by reference net_dim() is currently passed a struct dim_sample argument by value. struct dim_sample is 24 bytes. Since this is greater 16 bytes, x86-64 passes it on the stack. All callers have already initialized dim_sample on the stack, so passing it by value requires pushing a duplicated copy to the stack. Either witing to the stack and immediately reading it, or perhaps dereferencing addresses relative to the stack pointer in a chain of push instructions, seems to perform quite poorly. In a heavy TCP workload, mlx5e_handle_rx_dim() consumes 3% of CPU time, 94% of which is attributed to the first push instruction to copy dim_sample on the stack for the call to net_dim(): // Call ktime_get() 0.26 |4ead2: call 4ead7 // Pass the address of struct dim in %rdi |4ead7: lea 0x3d0(%rbx),%rdi // Set dim_sample.pkt_ctr |4eade: mov %r13d,0x8(%rsp) // Set dim_sample.byte_ctr |4eae3: mov %r12d,0xc(%rsp) // Set dim_sample.event_ctr 0.15 |4eae8: mov %bp,0x10(%rsp) // Duplicate dim_sample on the stack 94.16 |4eaed: push 0x10(%rsp) 2.79 |4eaf1: push 0x10(%rsp) 0.07 |4eaf5: push %rax // Call net_dim() 0.21 |4eaf6: call 4eafb To allow the caller to reuse the struct dim_sample already on the stack, pass the struct dim_sample by reference to net_dim(). Signed-off-by: Caleb Sander Mateos Reviewed-by: Vladimir Oltean Reviewed-by: Shannon Nelson Reviewed-by: Florian Fainelli Reviewed-by: Arthur Kiyanovski Reviewed-by: Louis Peens Link: https://patch.msgid.link/20241031002326.3426181-2-csander@purestorage.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/netronome/nfp/nfd3/dp.c | 4 ++-- drivers/net/ethernet/netronome/nfp/nfdk/dp.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) (limited to 'drivers/net/ethernet/netronome') diff --git a/drivers/net/ethernet/netronome/nfp/nfd3/dp.c b/drivers/net/ethernet/netronome/nfp/nfd3/dp.c index d215efc6cad0..f1c6c47564b1 100644 --- a/drivers/net/ethernet/netronome/nfp/nfd3/dp.c +++ b/drivers/net/ethernet/netronome/nfp/nfd3/dp.c @@ -1179,7 +1179,7 @@ int nfp_nfd3_poll(struct napi_struct *napi, int budget) } while (u64_stats_fetch_retry(&r_vec->rx_sync, start)); dim_update_sample(r_vec->event_ctr, pkts, bytes, &dim_sample); - net_dim(&r_vec->rx_dim, dim_sample); + net_dim(&r_vec->rx_dim, &dim_sample); } if (r_vec->nfp_net->tx_coalesce_adapt_on && r_vec->tx_ring) { @@ -1194,7 +1194,7 @@ int nfp_nfd3_poll(struct napi_struct *napi, int budget) } while (u64_stats_fetch_retry(&r_vec->tx_sync, start)); dim_update_sample(r_vec->event_ctr, pkts, bytes, &dim_sample); - net_dim(&r_vec->tx_dim, dim_sample); + net_dim(&r_vec->tx_dim, &dim_sample); } return pkts_polled; diff --git a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c index dae5af7d1845..ebeb6ab4465c 100644 --- a/drivers/net/ethernet/netronome/nfp/nfdk/dp.c +++ b/drivers/net/ethernet/netronome/nfp/nfdk/dp.c @@ -1289,7 +1289,7 @@ int nfp_nfdk_poll(struct napi_struct *napi, int budget) } while (u64_stats_fetch_retry(&r_vec->rx_sync, start)); dim_update_sample(r_vec->event_ctr, pkts, bytes, &dim_sample); - net_dim(&r_vec->rx_dim, dim_sample); + net_dim(&r_vec->rx_dim, &dim_sample); } if (r_vec->nfp_net->tx_coalesce_adapt_on && r_vec->tx_ring) { @@ -1304,7 +1304,7 @@ int nfp_nfdk_poll(struct napi_struct *napi, int budget) } while (u64_stats_fetch_retry(&r_vec->tx_sync, start)); dim_update_sample(r_vec->event_ctr, pkts, bytes, &dim_sample); - net_dim(&r_vec->tx_dim, dim_sample); + net_dim(&r_vec->tx_dim, &dim_sample); } return pkts_polled; -- cgit