From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTP id 5E3BF5A004F for ; Fri, 26 Jul 2024 10:01:38 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721980897; 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=w5HRGPe61LhYfZ70ZMUW1xKgnRe8w3UT4kB4H4uxxoM=; b=GThqNwTb3sid4rfDCSdozLmeeXP0fOymx5VBkOVp62lmRBx2WgehOivZfoa9y6g/2cZ5qK OcLa8K+2v5WgCzqYIaFwnfECeJgI7GzM7eG+NSp0qM1bpAZMZOLihZY76uNry5QTEsZgDI g294qVjK/TeFZSQnO14+fVAKYQ0Q8Mg= Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-398-hOy7c765NP6XIPRFxhwrVA-1; Fri, 26 Jul 2024 04:01:33 -0400 X-MC-Unique: hOy7c765NP6XIPRFxhwrVA-1 Received: by mail-qk1-f197.google.com with SMTP id af79cd13be357-7a1ddd9812aso58567785a.2 for ; Fri, 26 Jul 2024 01:01:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721980892; x=1722585692; h=content-transfer-encoding:mime-version:organization:references :in-reply-to:message-id:subject:cc:to:from:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=w5HRGPe61LhYfZ70ZMUW1xKgnRe8w3UT4kB4H4uxxoM=; b=cHRAVW4YBkbz/JrixoNWY1RpnRn4fVwtFIWxdzRp37ZEVsuI7A1EcQJBJJbRolICi4 lhH8jqUMh45A27gSm3e/qcuJ2QEIa42SSz/U1bOc3IBzXwIxXFJfqTL6ViIzf11XajIH 3a/ykCh4K0zDaFk2l41H6qpvjBLseb6tCRG2an1EwxWYCalY1No/hJ6AHSpD703SbUHU 9/8g551VvaXoMKho57wy/L0OjitVfBF5qybiSaPd0gaZzYA8nTwheBarvGpaLyoK5GMk rczmiI3RmVMou56MqrYaKNJgUqEvDkBqxTnvPJDFQkVPAOYXGx/6CYzgR0d2NqZG7G8M nYqg== X-Gm-Message-State: AOJu0YxSaGKlx06sjjATfhHasxUOPZ3wDR8nCoUvP3LbXkPBo6wTToHv Vylx3UhA1BNOG5Jqc5xDQfQkjuzOygUzO0hQJwBNDxufibDbN6pV8YCHk8+hajrM8zg5UyUdk2n AsVPQa+TtOJ1HzQCAIZstvonJIqN8Rf2qj/fk69tv1Nrb5aO8D+WZ8r+GGQIk X-Received: by 2002:a05:620a:424d:b0:79f:8c4:114e with SMTP id af79cd13be357-7a1d7f6808bmr448182985a.70.1721980892151; Fri, 26 Jul 2024 01:01:32 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGBY7SEHE6fyuXj5wkEd8pNGPFocp9g4riPttcJXM2HaNHiNMv/grcZPb2qzMDiP3M4pPudug== X-Received: by 2002:a05:620a:424d:b0:79f:8c4:114e with SMTP id af79cd13be357-7a1d7f6808bmr448180685a.70.1721980891789; Fri, 26 Jul 2024 01:01:31 -0700 (PDT) Received: from maya.cloud.tilaa.com (maya.cloud.tilaa.com. [164.138.29.33]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7a1d73b1647sm154087585a.28.2024.07.26.01.01.30 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Jul 2024 01:01:30 -0700 (PDT) Date: Fri, 26 Jul 2024 10:00:56 +0200 From: Stefano Brivio To: David Gibson Subject: Re: [PATCH 3/5] tap: Don't use EPOLLET on Qemu sockets Message-ID: <20240726100056.235b65de@elisabeth> In-Reply-To: <20240726072031.3941305-4-david@gibson.dropbear.id.au> References: <20240726072031.3941305-1-david@gibson.dropbear.id.au> <20240726072031.3941305-4-david@gibson.dropbear.id.au> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: LHC2HQMRI23F4D3HS3EAMD4XARIBTSHM X-Message-ID-Hash: LHC2HQMRI23F4D3HS3EAMD4XARIBTSHM 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 Fri, 26 Jul 2024 17:20:29 +1000 David Gibson wrote: > Currently we set EPOLLET (edge trigger) on the epoll flags for the > connected Qemu Unix socket. It's not clear that there's a reason for > doing this: for TCP sockets we need to use EPOLLET, because we leave data > in the socket buffers for our flow control handling. That consideration > doesn't apply to the way we handle the qemu socket however. It significantly decreases epoll_wait() overhead on sustained data transfers, because we can read multiple TAP_BUF_SIZE buffers at a time instead of just one. I can check that now again with current QEMU and kernel versions, plus several fundamental changes in buffer handling, but I don't see a real reason why this shouldn't have changed meanwhile. -- Stefano