From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: passt.top; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=MZkMhIq7; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTPS id 773775A026D for ; Thu, 04 Jun 2026 06:41:48 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1780548107; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=oFjuW/kvoxvbLJqFMalRF5LcY1UkxNhoG5OfZy9UIQI=; b=MZkMhIq7Dl6jUJJ88jj3H4PCr7TaaePHGGJJ2PTYE1ULvW1NQ0UDTX/XV68Ty4eMc8tRX3 FGSU4aCpvRUm5nBFATUmEBPP1UdEZNWAGkYHwQKv1aatbgdHSqOqV0ql4fnX3sFPLeokHf Zo6/VXFryBYJg50g3Z6ieLxcGsNH0sc= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-124-7d2aOKuLNNmfApzZNVAVSQ-1; Thu, 04 Jun 2026 00:41:46 -0400 X-MC-Unique: 7d2aOKuLNNmfApzZNVAVSQ-1 X-Mimecast-MFC-AGG-ID: 7d2aOKuLNNmfApzZNVAVSQ_1780548105 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-490a786f987so3081875e9.3 for ; Wed, 03 Jun 2026 21:41:45 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780548105; x=1781152905; h=date:content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=oFjuW/kvoxvbLJqFMalRF5LcY1UkxNhoG5OfZy9UIQI=; b=X8lfjb9gVjX0zZvQ5Q0/1pgyIOAHeLIvjwL2FSUdfUq+mFjkiT1tvaYfpE8+BWWwTc 8QYQt0TW5IH2kN6QPd4M/yZsnxAzMiMcHPIoI7+s/T0m5H9yiHCu4ltWf/GRObK3q70p WaVfKHieGcroUBuvjrNzsF7Y5fLh5EjCKj0T+iq+1YKS1KZrbF4LwlgexIZ4H2Q2v3LH YHiinOMj0JZziXmSY0M60d1ZL9IbsWQGVCWHi6NeGbUdIHJp0ejH1hgmQdxOsExnyCL+ TgwO3ZPOkR776tjptQP3oMe63lkL3vAStsPaWiQfwPGWAKbwQBhiBbR7jmNSVnUpK6IZ S9Bw== X-Gm-Message-State: AOJu0YxFovExzDQ96ftGVA3oIRI9gfNzzHLDQ+0J082zYsoBG5ccsuHf 47alPsEuwaKKDDBB8/frbgGgkqgpa53gyv9OYhgyCEPsc3dZeaSS7CVmRJAWckXHbPJOmNjjGBj mDlIH0loiFghiXUeeJw33rGEol/Vw15ZZ1rSX+nGUDVAkz59eHHiLrrMRQnj8oQ== X-Gm-Gg: Acq92OHTWVFg2GpAn6AlYK6qcPdTdFzSeQUi9bc6/daUd4G4oWT/rgbPF+jxNNj8vPU CDXeK0Glt1LDZLu4U7A/Bo8LpcYrHTEX2FqYq7QIoTPOz8riqlrWp4/r3QqMyefQBFKjOS2D+py esnoX5E38AqED1PqideWJOAXBDgoZPKbCtdtZhn9BaFdDJlZN7YU1O8vLDS/LlSlzYXvfqKE7B4 Wr2oMHvBk2xOFN1CUbmlHQKGnp5sWZEgOAE4NVTlTIVbECUZrMBLQ+2F6NOYekIXLZ20xMhZUVN L01iSu46LMYD0nujheEglVr2NjUOUYuE+xPZ/2FHNJBxzRqg+DHenUqE9/2e+OQV9r9PeuqYA4t cyYOD6usi/JqpFkDjiQrnkHFtmQxb8RhRpbUNZeZxW6I= X-Received: by 2002:a05:600c:5288:b0:490:b0f1:c27e with SMTP id 5b1f17b1804b1-490b5ee1c64mr103630915e9.24.1780548104822; Wed, 03 Jun 2026 21:41:44 -0700 (PDT) X-Received: by 2002:a05:600c:5288:b0:490:b0f1:c27e with SMTP id 5b1f17b1804b1-490b5ee1c64mr103630615e9.24.1780548104278; Wed, 03 Jun 2026 21:41:44 -0700 (PDT) Received: from maya.myfinge.rs (ifcgrfdd.trafficplex.cloud. [2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f351d69sm21657467f8f.29.2026.06.03.21.41.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jun 2026 21:41:43 -0700 (PDT) From: Stefano Brivio To: David Gibson Subject: Re: [PATCH 7/8] tcp_splice: Remove questionable "optimisation" of pending bytes tracking Message-ID: <20260604064142.5abdaced@elisabeth> In-Reply-To: <20260528050213.679685-8-david@gibson.dropbear.id.au> References: <20260528050213.679685-1-david@gibson.dropbear.id.au> <20260528050213.679685-8-david@gibson.dropbear.id.au> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) MIME-Version: 1.0 Date: Thu, 04 Jun 2026 06:41:43 +0200 (CEST) X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: b8aAAj1-HP38DTsuJr7mCqYYVCLkrrP0TsJ3UHjOYks_1780548105 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: XYJ5TUMH74M5UEHRJUIERRR7BQKUJXS3 X-Message-ID-Hash: XYJ5TUMH74M5UEHRJUIERRR7BQKUJXS3 X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Thu, 28 May 2026 15:02:12 +1000 David Gibson wrote: > We have a special path that avoids updating conn->pending when the amounts > read and written are equal. This has a conceptual complexity cost, in > particular, it means that conn->pending[] is not accurate to its normal > meaning for a section of the loop body. > > conn->pending[] shares a cacheline with conn->pipe[] and conn->s[], so it's > almost certainly cache-hot. It's questionable that avoiding the update > of pending even outweighs the extra conditional branch, let alone saves > anything of significance. Remove it. I added this when we still had 64-bit counters, that is, two weeks before commit 37c228ada88b ("tap, tcp, udp, icmp: Cut down on some oversized buffers"), but now, as you point out, it doesn't make sense anymore. -- Stefano