From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ferruh Yigit Subject: Re: possible kni bug and proposed fix Date: Tue, 17 May 2016 11:07:27 +0100 Message-ID: <573AED5F.3080105@intel.com> References: <5739ACFF.4000506@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: dev@dpdk.org To: ALeX Wang Return-path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 3E9DE69FF for ; Tue, 17 May 2016 12:07:35 +0200 (CEST) In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 5/16/2016 4:31 PM, ALeX Wang wrote: > Hi Ferruh, >=20 > Thx for pointing out the 'fill alloc_q with these mubfs _until it gets > full_.', >=20 > I saw the size of all queues are 'KNI_FIFO_COUNT_MAX (1024)'... > The corresponding memory required is more than what I specify as > 'socket_mem' (since i'm using VM)... >=20 If the mempool is not big enough to fill the ring, this explains the error log. Logic is to fill the alloc_q, but if you are missing the required mbufs, in each rte_kni_rx_burst() it will complain about memory. But the required memory for mbufs to fill the ring is not too much. It should be ~2Mbytes, are you sure you are missing this much memory? > Also, in my use case, I only `tcpreplay` through the kni interface, and > my application only do rx and then free the 'mbufs'. So there is no tx > at all. >=20 > So, in my case, I still think this is a bug/defect, or somewhere i stil= l > misunderstand, >=20 > P.S. The description here seems to be inverted, > http://dpdk.org/doc/api/rte__kni_8h.html#a0cdd727cdc227d005fef22c0189f3= dfe > 'rte_kni_rx_burst' does the 'It handles allocating the mbufs for KNI > interface alloc queue.' >=20 You are right. That part of the description for rte_kni_rx_burst and rte_kni_tx_burst needs to be replaced. Do you want to send a patch? > Thanks, > Alex Wang, >=20 > On 16 May 2016 at 04:20, Ferruh Yigit > wrote: >=20 > On 5/15/2016 5:48 AM, ALeX Wang wrote: > > Hi, > > > > When using the kni module to test my application inside > > debian (virtualbox) VM (kernel version 4.4), I get the > > > > "KNI: Out of memory" > > > > from syslog every time I `tcpreply` packets through > > the kni interface. > > > > After checking source code, I saw that when I call > > 'rte_kni_rx_burst()', no matter how many packets > > are actually retrieved, we always call 'kni_allocate_mbufs()' > > and try allocate 'MAX_MBUF_BURST_NUM' more > > mbufs... I fix the issue via using this patch below, > > > > Could you confirm if this is an actual bug? > > >=20 > Hi Alex, >=20 > I don't think this is a bug. >=20 > kni_allocate_mbufs() will allocate MAX_MBUF_BURST_NUM mbufs as you > mentioned. And will fill alloc_q with these mubfs _until it gets fu= ll_. > And if the alloc_q is full and there are remaining mbufs, they will= be > freed. So for some cases this isn't the most optimized way, but the= re is > no defect. >=20 > Since you are getting "KNI: Out of memory", somewhere else can be > missing freeing mbufs. >=20 > mbufs freeing done in rte_kni_tx_burst(), I can guess two cases tha= t can > cause problem: > a) not calling rte_kni_tx_burst() frequent, so that all free mbufs > consumed. > b) calling rte_kni_tx_burst() with number of mbufs bigger than > MAX_MBUF_BURST_NUM, because this function frees at most > MAX_MBUF_BURST_NUM of mbufs, but if you are calling calling > rte_kni_tx_burst() with bigger numbers, this will cause mbufs to st= uck > in free_q >=20 >=20 > Regards, > ferruh >=20 >=20 >=20 >=20 >=20 > --=20 > Alex Wang, > Open vSwitch developer