From owner-freebsd-net@FreeBSD.ORG Mon Aug 23 19:16:38 2010 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id BAC1E1065695; Mon, 23 Aug 2010 19:16:38 +0000 (UTC) (envelope-from pyunyh@gmail.com) Received: from mail-px0-f182.google.com (mail-px0-f182.google.com [209.85.212.182]) by mx1.freebsd.org (Postfix) with ESMTP id 8047D8FC20; Mon, 23 Aug 2010 19:16:38 +0000 (UTC) Received: by pxi17 with SMTP id 17so2676151pxi.13 for ; Mon, 23 Aug 2010 12:16:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:received:from:date:to:cc :subject:message-id:reply-to:references:mime-version:content-type :content-disposition:in-reply-to:user-agent; bh=aU2dLrfjAy6ogpcR1phGHwJqmzRKaK3kbjDEz7fCZAw=; b=DkFYVonWtJF1YIrFQJPM7EqHq2Hx0G20DaWtgJnm823CXNsEF8JULmhXCaEu6UK9uW mjsEs59i0PvPHVtgSxs7H2TMFfZ1m3k9z8038o4dY9MwggXwyTQMuaN3LauDStSBl3N1 I6lF/OaVE7kAjTUO0xQ4/h8H2v9o9qjX3CjWE= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:date:to:cc:subject:message-id:reply-to:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=sjhNaGJedMopn+1q7Zu2kO+cYVR1LE5DAjSOji4FFahI8tUdYuOD7r4sWAQzJDgE7P LO3NJSKzwo7gaJWkT+PGY/2qwsn5wFlKBTV3soaLGsqDfEps5Cswrzz1+GH3HEj9Trws NRnbMt4DQb96dC141O7GT95jEZ2IBM2Z5k5xs= Received: by 10.114.134.9 with SMTP id h9mr6577237wad.5.1282590998017; Mon, 23 Aug 2010 12:16:38 -0700 (PDT) Received: from pyunyh@gmail.com ([174.35.1.224]) by mx.google.com with ESMTPS id 33sm13062653wad.6.2010.08.23.12.16.35 (version=TLSv1/SSLv3 cipher=RC4-MD5); Mon, 23 Aug 2010 12:16:36 -0700 (PDT) Received: by pyunyh@gmail.com (sSMTP sendmail emulation); Mon, 23 Aug 2010 12:16:34 -0700 From: Pyun YongHyeon Date: Mon, 23 Aug 2010 12:16:34 -0700 To: Andre Oppermann Message-ID: <20100823191634.GE1116@michelle.cdnetworks.com> References: <20100822222746.GC6013@michelle.cdnetworks.com> <4C724AD9.5020000@freebsd.org> <20100823175220.GB1116@michelle.cdnetworks.com> <4C72C622.2070302@freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C72C622.2070302@freebsd.org> User-Agent: Mutt/1.4.2.3i Cc: adrian.chadd@gmail.com, freebsd-net@freebsd.org Subject: Re: 8.0-RELEASE-p3: 4k jumbo mbuf cluster exhaustion X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: pyunyh@gmail.com List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 23 Aug 2010 19:16:38 -0000 On Mon, Aug 23, 2010 at 09:04:02PM +0200, Andre Oppermann wrote: > On 23.08.2010 19:52, Pyun YongHyeon wrote: > >On Mon, Aug 23, 2010 at 12:18:01PM +0200, Andre Oppermann wrote: > >>On 23.08.2010 11:26, Adrian Chadd wrote: > >>>On 23 August 2010 06:27, Pyun YongHyeon wrote: > >>> > >>>>I recall there was SIOCSIFCAP ioctl handling bug in bce(4) on 8.0 so > >>>>it might also disable IFCAP_TSO4/IFCAP_TXCSUM/IFCAP_RXCSUM when yo > >>>>disabled RX checksum offloading. But I can't explain how checksum > >>>>offloading could be related with the growth of 4k jumbo buffers. > >>> > >>>Neither can I! > >>> > >>>I'm trying to come up with a reproduction method that doesn't involve > >>>"put box on the internet, push clients through it, wait." > >> > >>Network drivers use 2k sized mbuf clusters on receive. So the problem > >>doesn't seem to be RX related. > >> > > > >bce(4) is special in this regards. The controller would allocate > >jumbo cluster on RX if jumbo frame is used. If header splitting is > >used, driver will use normal mbuf clusters. > > Didn't know that. > > >>The function that is called on a socket write is sosend_generic() which > >>makes use of m_getm2(). This function allocates mbuf chains with the > >>tightest packing it can achieve. It will make use 4k (page size) mbufs > >>as much as it can. This is where they come from. > >> > >>It seems the 4k clusters do not get freed back to the pool after they've > >>been sent by the NIC and dropped from the socket buffer after the ACK has > >>arrived. The leak must occur in one of these two places. The socket > >>buffer is unlikely as it would affect not just you but everyone else too. > >>Thus the mbuf freeing after DMA/tx in the bce(4) driver is the prime > >>suspect. > >> > > > >I know bce(4) has a couple of bug in TX path(wrong dma tag, lack of > >bus_dmamap_sync(9) etc) but this is the same code path with/without > >TX checksum offloading. This is one of reason why I still do not > >understand what's really happening here. TX checksum offloading may > >introduce additional frame processing time to fill internal FIFO to > >compute checksum before transmitting the frame to wire such that it > >can change timing of TX path. This timing change might trigger the > >TX path bug. It's just vague guessing though. > > Had a chat with Claudio@OpenBSD and he said that the bce(4) DMA engine > can only access the first 1GB of physical RAM and has to use bounce > buffers all the time. Maybe this is related. > Really? I don't remember I saw such a DMA address space limitation in data sheet. And I don't think Broadcom made such a horrible thing for controllers targeted for servers. The only limitation I know is BCM5708 is not able to handle DMA addresses greater than 40bits so bce(4) limits the DMA address space in DMA tag creation.