From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yw1-f201.google.com (mail-yw1-f201.google.com [209.85.128.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 113F8131BA3 for ; Thu, 28 Mar 2024 17:03:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711645399; cv=none; b=IemnSaljglBFV0uCEJA+1gDbI7NJIy2eP5mI02i+jNkvZ+xUzhGgtYRk1RjTss9FwyixDA5Wr4Gz2+FfwFocby9jdXeTUS6YwMBtDQoxcpkrjmhh5sDibtsDSzz6C10BSaoJwfqCtcUd+8H7r4OYkVJBPxnYMukL0dxF/4Rsdkg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711645399; c=relaxed/simple; bh=dN/v+E0kL8WG56Mv6N2bzCQJg+7TLsKE8PqoMrU1wOs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=FH6IIeja1+p3J+csPgpBrYvUXm2K3IJUEycGvWbhYMHmf2vkZYGIsF5DUU2nE7uhaedcsBvtKmegy1mACoBia/OIi7JNGQB8gsxFhQIbLnGessjglfGhFJFprZmp5K4Obj1BWFkGi/5mTKYiBqyXaNf9+fRtZDzpeFrhJEeR/VM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=gOxJmiUC; arc=none smtp.client-ip=209.85.128.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--edumazet.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="gOxJmiUC" Received: by mail-yw1-f201.google.com with SMTP id 00721157ae682-60a54004e9fso21966967b3.3 for ; Thu, 28 Mar 2024 10:03:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1711645397; x=1712250197; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=rg1OdI5e7r+RvUDxZBQUJCmu93WtBEz8eFjqLMQtw/s=; b=gOxJmiUCuBO2hh0GC93Hi7fGru8z+Qm57jdyKKq9NCu3C1A4jiSQ8k6er3kx0hTqID fCA4ZpgGTL/N1jp+ixsGEas5gB8O37x75A4tb5NDAI6WdiY1vyOn1e6OHzbA8tm04To1 wloloD+uUrNqc4BCBSdrU0P5iDPFP6HNBGnWIy26jCSgblxLqQyzKfIayK1e+R2Syrpc Gwtr/QhvnvUZQfPgfsF0+bORDVMIRw+mwPld3QHf/LaNHMOHs8GclyAYtWC5ZIojilVv P5Tu61keRyGSkzw5+GjMxojLhbB2rNujFpQGop3yvQ7h7gS77PSilK5x9u3+6NbjgqcJ 6WEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1711645397; x=1712250197; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=rg1OdI5e7r+RvUDxZBQUJCmu93WtBEz8eFjqLMQtw/s=; b=HGkbhhj2ke7cGuxLBBuJ+jutL6Lavlhx9A3CSJCX0pwBC2YFm6+Bg10k0nXefu8pZi qQYzKJuZEUvZEtNA6oMgfWOL1wL8eCCXszPmUEvYn+GQCh5v0XdJEwjuqe5915LSpnFs EU433QGQ7KnL4GPNkUrGSfPGKpQ1ScukNLhtWniTlaXMwk/lUqaqBACoRWzcvtL4O3CK Fe0lCp8aG8ZYm3vmwn/GKl8Edy7NmXf1XtZUCovfoJUxBQ4PGTQI5gW93px3EtrbGG7j /OW0Kt+K3jib62W20TDy+Gv6tX+JZ528W3LgTshazKF8tChS5/gYt6FcZaU9zYWq6H8b mM2A== X-Gm-Message-State: AOJu0Yz9bwovV75iCkqeLY8xdDhPsD9vxv6dOgw3u+jAxtiP/+6XbcoA z/me2cdSjxS+BYQ5J0+Z32PDBf4VlWGcofoAlqsA5eZeQxoFNzWbkYbbqY4txu2p3kTtekjOjX8 Jh35EL6X0ag== X-Google-Smtp-Source: AGHT+IF2+6girXyoZaFPLNw3BWl6MtVk49zlLOSIu82lkK8jgxX7qHHaqDCEGz0PHoNvFGso/t8yAx3w8HMrCg== X-Received: from edumazet1.c.googlers.com ([fda3:e722:ac3:cc00:2b:7d90:c0a8:395a]) (user=edumazet job=sendgmr) by 2002:a81:6dd0:0:b0:611:34aa:ea6e with SMTP id i199-20020a816dd0000000b0061134aaea6emr4392ywc.1.1711645397135; Thu, 28 Mar 2024 10:03:17 -0700 (PDT) Date: Thu, 28 Mar 2024 17:03:05 +0000 In-Reply-To: <20240328170309.2172584-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240328170309.2172584-1-edumazet@google.com> X-Mailer: git-send-email 2.44.0.478.gd926399ef9-goog Message-ID: <20240328170309.2172584-5-edumazet@google.com> Subject: [PATCH net-next 4/8] net: make softnet_data.dropped an atomic_t From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet Content-Type: text/plain; charset="UTF-8" If under extreme cpu backlog pressure enqueue_to_backlog() has to drop a packet, it could do this without dirtying a cache line and potentially slowing down the target cpu. Move sd->dropped into a separate cache line, and make it atomic. In non pressure mode, this field is not touched, no need to consume valuable space in a hot cache line. Signed-off-by: Eric Dumazet --- include/linux/netdevice.h | 3 ++- net/core/dev.c | 13 +++++++++---- net/core/net-procfs.c | 3 ++- 3 files changed, 13 insertions(+), 6 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 70775021cc269e0983f538619115237b0067d408..1c31cd2691d32064613836141fbdeeebc831b21f 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3236,10 +3236,11 @@ struct softnet_data { unsigned int input_queue_tail; #endif unsigned int received_rps; - unsigned int dropped; struct sk_buff_head input_pkt_queue; struct napi_struct backlog; + atomic_t dropped ____cacheline_aligned_in_smp; + /* Another possibly contended cache line */ spinlock_t defer_lock ____cacheline_aligned_in_smp; int defer_count; diff --git a/net/core/dev.c b/net/core/dev.c index af7a34b0a7d6683c6ffb21dd3388ed678473d95e..be2392ba56bc57bed456e2748b332d4971c83a4e 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4790,17 +4790,22 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, struct softnet_data *sd; unsigned long flags; unsigned int qlen; + int max_backlog; reason = SKB_DROP_REASON_DEV_READY; if (!netif_running(skb->dev)) goto bad_dev; + reason = SKB_DROP_REASON_CPU_BACKLOG; sd = &per_cpu(softnet_data, cpu); + qlen = skb_queue_len_lockless(&sd->input_pkt_queue); + max_backlog = READ_ONCE(net_hotdata.max_backlog); + if (unlikely(qlen > max_backlog)) + goto cpu_backlog_drop; backlog_lock_irq_save(sd, &flags); qlen = skb_queue_len(&sd->input_pkt_queue); - if (qlen <= READ_ONCE(net_hotdata.max_backlog) && - !skb_flow_limit(skb, qlen)) { + if (qlen <= max_backlog && !skb_flow_limit(skb, qlen)) { if (qlen) { enqueue: __skb_queue_tail(&sd->input_pkt_queue, skb); @@ -4816,11 +4821,11 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu, napi_schedule_rps(sd); goto enqueue; } - reason = SKB_DROP_REASON_CPU_BACKLOG; - sd->dropped++; backlog_unlock_irq_restore(sd, &flags); +cpu_backlog_drop: + atomic_inc(&sd->dropped); bad_dev: dev_core_stats_rx_dropped_inc(skb->dev); kfree_skb_reason(skb, reason); diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c index a97eceb84e61ec347ad132ff0f22c8ce82f12e90..fa6d3969734a6ec154c3444d1b25ee93edfc5588 100644 --- a/net/core/net-procfs.c +++ b/net/core/net-procfs.c @@ -144,7 +144,8 @@ static int softnet_seq_show(struct seq_file *seq, void *v) seq_printf(seq, "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x " "%08x %08x\n", - sd->processed, sd->dropped, sd->time_squeeze, 0, + sd->processed, atomic_read(&sd->dropped), + sd->time_squeeze, 0, 0, 0, 0, 0, /* was fastroute */ 0, /* was cpu_collision */ sd->received_rps, flow_limit_count, -- 2.44.0.478.gd926399ef9-goog