From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-x234.google.com (mail-pd0-x234.google.com [IPv6:2607:f8b0:400e:c02::234]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 2762C21F4FD for ; Tue, 16 Jun 2015 11:12:41 -0700 (PDT) Received: by pdjn11 with SMTP id n11so19670052pdj.0 for ; Tue, 16 Jun 2015 11:12:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:subject:from:to:cc:date:in-reply-to:references :content-type:mime-version:content-transfer-encoding; bh=8BvAQ/GyISD46lqOYkRnvvYnLGe0kxmrxS6QERSan/M=; b=cfs77sBiuj2ktq2DQas1ozknfFQ0HmSSV3bg77x7ecWuPVxJINZXV93lLR5yNTrK2V 3LendoA77zWJn+89dizplgWQ9vMkhQNaqgwWtCc7KAX3zSZdiqef7nEPPx0KBqxs9QMX f9AGj4hZV2esj2On+ZYpNDprEfaZbpnPdGHJtP7CSwbGSWw7ucjY37Y6F2qm2RvKyjYR 3pTm+PmK3EHLi8HrblebkVRiVCwDv5pgyz5o5TgtSGrvQl2rm9E5rZmcskDs9f0GPU0e tTo7xDw1gX+YBSJ3gwEA16H2aXM6pgyeR2ykPvhERMrzS2oe4SX2DtQdAUd4i3rmeePK gnYw== X-Received: by 10.66.221.193 with SMTP id qg1mr2807338pac.134.1434478359639; Tue, 16 Jun 2015 11:12:39 -0700 (PDT) Received: from [172.30.42.71] (c-71-202-136-89.hsd1.ca.comcast.net. [71.202.136.89]) by mx.google.com with ESMTPSA id ll6sm2085703pbc.28.2015.06.16.11.12.38 (version=TLSv1.2 cipher=AES128-GCM-SHA256 bits=128/128); Tue, 16 Jun 2015 11:12:38 -0700 (PDT) Message-ID: <1434478357.27504.185.camel@edumazet-glaptop2.roam.corp.google.com> From: Eric Dumazet To: Dave Taht Date: Tue, 16 Jun 2015 11:12:37 -0700 In-Reply-To: References: <20150616161807.GA31289@sesse.net> <1A30B531-745C-4323-9929-9EEBD94D775F@gmail.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.10.4-0ubuntu2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Cc: Jonathan Morton , bloat Subject: Re: [Bloat] using tcp_notsent_lowat in various apps? X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Jun 2015 18:13:10 -0000 On Tue, 2015-06-16 at 10:22 -0700, Dave Taht wrote: > Take samba as another potential example. I commonly see this > increasing the SO_SNDBUF to a given value, but I am not sure if this > is the right thing anymore. As samba is commonly used for filesharing > (and things that take locks and do database-y stuff), improving > interactivity might be a big win. > > Seeing the 50%! decrease in kernel memory on the original tests of > TCP_SENT_LOWAT is very exciting in the context of those running samba > on tiny tiny nas devices common in my world. > > And seeing apple enable it universally points to perhaps exploring the > effects of just enabling it universally in linux (or in certain kinds > of linux-based devices) at a "reasonable" value, for whatever value of > reasonable exists. Another use case for TCP_SENT_LOWAT is the cancel phase. If for one reason, application decides to abort the transfer, by doing a close() or shutdown(), it is better to have at most few KB of data still queued in socket, that kernel tries to deliver no matter what. I've seen stupid applications having timeouts on their sockets. When they believe a flow is stuck, they close it and open a new one. And you get many flows competing on the same bottleneck.