From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 1wt.eu (ded1.1wt.eu [163.172.96.212]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3FAC8267706 for ; Fri, 14 Feb 2025 17:12:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=163.172.96.212 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739553150; cv=none; b=jg1DtUUDyMEayRkTtBs1x6DlIgLl+2FQx9h5KhEdmE8dRdMUSJczKk1L24OSFpso/fRttimR0fT+3nnhyjIjDhA0ZBJZ33eOoejcd1AjVTYXhKVKf/BIfkI+LL7BKPWVQTvfqmy8qlAIDQkzMJeddormfUfIrqqrBD+bEr19fZA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739553150; c=relaxed/simple; bh=p4vP18wp2b9vouSv8sBf2Lb3K/dssY4LCr/9/FDOvhE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EQRSB444OW1TKumtxmWc92U3lytjTzil1pUy4c2up8Wk8EQeNZ3coTuYyM7zWO5J1LE9AACvcE39uSuHwpX39VRbjmrz0HdZF70LONptJ3G3LgtyNBPKGBIW6vgM5EXMa0jKjqe16cffknDdiAs2ltJkhWhv6AvlaXT0HZjec2A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=1wt.eu; spf=pass smtp.mailfrom=1wt.eu; arc=none smtp.client-ip=163.172.96.212 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=1wt.eu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=1wt.eu Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 51EHCJ7s008258; Fri, 14 Feb 2025 18:12:19 +0100 Date: Fri, 14 Feb 2025 18:12:19 +0100 From: Willy Tarreau To: ??? Cc: netdev@vger.kernel.org Subject: Re: Question about TCP delayed-ack and PUSH flag behavior Message-ID: <20250214171219.GA8209@1wt.eu> References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) On Fri, Feb 14, 2025 at 12:03:17PM -0500, ??? wrote: > Hi netdev, > > When tcp stack receives a segment with PUSH flag set, does the stack > immediately send out for the corresponding ACK with ignoring delay-ack > timer? > Or regardless of the PUSH flag, delay-ack is always enforced? It depends, it's possible for the application to force a delayed ack by setting TCP_QUICKACK to zero. This is convenient for web servers that know they respond quickly and can merge this ack with the response to save one packet. Willy