From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?utf-8?Q?Bj=C3=B8rn_Mork?= Subject: Re: [PATCH net 2/3] net: cdc_mbim: send ZLP after max sized NTBs Date: Mon, 21 Jan 2013 23:36:49 +0100 Message-ID: <878v7mb1tq.fsf@nemi.mork.no> References: <1358783440-11459-1-git-send-email-bjorn@mork.no> <1358783440-11459-3-git-send-email-bjorn@mork.no> <2AC7D4AD8BA1C640B4C60C61C8E520154A8EE17D57@EXDCVYMBSTM006.EQ1STM.local> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "netdev\@vger.kernel.org" , "linux-usb\@vger.kernel.org" , Greg Suarez , Oliver Neukum , Alexey Orishko To: Alexey ORISHKO Return-path: Received: from canardo.mork.no ([148.122.252.1]:44771 "EHLO canardo.mork.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752365Ab3AUWhm convert rfc822-to-8bit (ORCPT ); Mon, 21 Jan 2013 17:37:42 -0500 In-Reply-To: <2AC7D4AD8BA1C640B4C60C61C8E520154A8EE17D57@EXDCVYMBSTM006.EQ1STM.local> (Alexey ORISHKO's message of "Mon, 21 Jan 2013 17:31:37 +0100") Sender: netdev-owner@vger.kernel.org List-ID: Alexey ORISHKO writes: >> -----Original Message----- >> From: Bj=C3=B8rn Mork [mailto:bjorn@mork.no] >>=20 >> We normally avoid sending ZLPs by padding NTBs with a zero byte if t= he >> NTB is shorter than dwNtbOutMaxSize, resulting in a short USB packet >> instead of a ZLP. But in the case where the NTB length is exactly >> dwNtbOutMaxSize and this is an exact multiplum of wMaxPacketSize, th= en >> we must send a ZLP. >>=20 >> This fixes an issue seen on a Sierra Wireless MC7710 device where th= e >> transmission would fail whenever we ended up padding the NTBs to max >> size. > > If you add ZLP for NTBs of dwNtbOutMaxSize, you are heavily affecting= CPU > load, increasing interrupt load by factor of 2 in high load traffic > scenario and possibly decreasing throughput for all other devices > which behaves correctly.=20 > > Why should others pay for Sierra Wireless fault? No, they shouldn't. > At least, do check VID/PID in usbnet and send ZLP only for malfunctio= ning=20 > devices. Yes, this would be easy to implement by simply creating a vendor/device specific entry in cdc_mbim. But I do worry that this isn't Sierra Wireless fault, but Qualcomms fault. SW are using Qualcomm firmware to do the low level stuff, and I know the Qualcomm firmware implement MBIM functionality so it may very well be the one to blame (I don't know this for sure, and I have no ide= a how to verify it). If this is correct than we can expect hundreds of devices needing a device specific entry in a year or two. That's not what I was looking forward to with a class driver like cdc_mbim. And I still believe that there is reason to ask if this is really a fault at all. I don't know if this is particularily useful, but here is an usbmon extract from the driver without the extra ZLP fix: ffff88022aef3d40 3883111197 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00060= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff880213f2d2c0 3883111233 S Bi:8:005:2 -115 16384 < ffff8802274eab40 3883111255 S Bi:8:005:2 -115 16384 < ffff88022fd65980 3883111276 S Bi:8:005:2 -115 16384 < ffff880204351440 3883111297 S Bi:8:005:2 -115 16384 < ffff880213f2d8c0 3883111317 S Bi:8:005:2 -115 16384 < ffff88022aef3d40 3883111460 C Bo:8:005:1 0 4096 > ffff880204351e00 3883965516 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00070= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff880204351e00 3883965849 C Bo:8:005:1 0 4096 > ffff880204351e00 3884973428 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00080= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff880204351e00 3884973752 C Bo:8:005:1 0 4096 > ffff880204351d40 3885981392 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00090= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff880204351d40 3885981638 C Bo:8:005:1 0 4096 > ffff880231b128c0 3886989391 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c000a0= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff880231b128c0 3886989622 C Bo:8:005:1 0 4096 > ffff8802041d8a40 3887997401 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c000b0= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff8802041d8a40 3887997675 C Bo:8:005:1 0 4096 > ffff8802041d8a40 3889005720 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c000c0= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff8802041d8a40 3889006019 C Bo:8:005:1 0 4096 > ffff8802041d8c80 3890013428 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c000d0= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff8802041d8c80 3890013784 C Bo:8:005:1 0 4096 > ffff880213f2d2c0 3892433962 C Bi:8:005:2 -104 0 ffff8802274eab40 3892434032 C Bi:8:005:2 -104 0 ffff88022fd65980 3892434078 C Bi:8:005:2 -104 0 ffff880204351440 3892434126 C Bi:8:005:2 -104 0 ffff880213f2d8c0 3892434172 C Bi:8:005:2 -104 0 same driver, with smaller packets keeping the NTB size below the magic limit: ffff88022b1de200 3896794916 S Bi:8:005:2 -115 16384 < ffff88022767d780 3896794928 C Bo:8:005:1 0 262 > ffff88022b1de140 3896794948 S Bi:8:005:2 -115 16384 < ffff88022767d780 3896794971 S Bi:8:005:2 -115 16384 < ffff88022b1deb00 3896794995 S Bi:8:005:2 -115 16384 < ffff88022767d900 3896864077 C Bi:8:005:2 0 416 =3D 4e434d48 0c003500 a0= 010c00 49505300 10000000 1c007a01 00000000 4500017a ffff88022767d900 3896864129 S Bi:8:005:2 -115 16384 < ffff88022d639e40 3897644729 S Bo:8:005:1 -115 262 =3D 4e434d48 0c000f00= 06010c00 49505300 10000000 b8004e00 00000000 00000000 ffff88022d639e40 3897644965 C Bo:8:005:1 0 262 > ffff88022b1de380 3897711770 C Bi:8:005:2 0 112 =3D 4e434d48 0c003600 70= 000c00 49505300 10000000 1c004e00 00000000 4500004e ffff88022b1de380 3897711812 S Bi:8:005:2 -115 16384 < ffff88022b07c600 3898646616 S Bo:8:005:1 -115 262 =3D 4e434d48 0c001000= 06010c00 49505300 10000000 b8004e00 00000000 00000000 ffff88022b07c600 3898646848 C Bo:8:005:1 0 262 > ffff88022b1de200 3898697788 C Bi:8:005:2 0 112 =3D 4e434d48 0c003700 70= 000c00 49505300 10000000 1c004e00 00000000 4500004e ffff88022b1de200 3898697829 S Bi:8:005:2 -115 16384 < ffff88022b1de140 3901425927 C Bi:8:005:2 -104 0 driver with ZLP: ffff8802041d82c0 3651255294 C Bo:8:005:1 0 4096 > ffff88021a3ef380 3652103000 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00320= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff88021a3ef380 3652103315 C Bo:8:005:1 0 4096 > ffff8802041af540 3652439129 C Bi:8:005:2 0 416 =3D 4e434d48 0c002c00 a0= 010c00 49505300 10000000 1c007a01 00000000 4500017a ffff8802041af540 3652439183 S Bi:8:005:2 -115 16384 < ffff8802041af240 3653099148 C Bi:8:005:2 0 416 =3D 4e434d48 0c002d00 a0= 010c00 49505300 10000000 1c007a01 00000000 4500017a ffff8802041af240 3653099183 S Bi:8:005:2 -115 16384 < ffff88021a3efb00 3653101946 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00330= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff88021a3efb00 3653102201 C Bo:8:005:1 0 4096 > ffff8802041af9c0 3654039362 C Bi:8:005:2 0 416 =3D 4e434d48 0c002e00 a0= 010c00 49505300 10000000 1c007a01 00000000 4500017a ffff8802041af9c0 3654039414 S Bi:8:005:2 -115 16384 < ffff88021a3ef980 3654101353 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00340= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff88021a3ef980 3654101622 C Bo:8:005:1 0 4096 > ffff88021a3efc80 3654999361 C Bi:8:005:2 0 416 =3D 4e434d48 0c002f00 a0= 010c00 49505300 10000000 1c007a01 00000000 4500017a ffff88021a3efc80 3654999412 S Bi:8:005:2 -115 16384 < ffff88021a3ef200 3655102396 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00350= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff88021a3ef200 3655102737 C Bo:8:005:1 0 4096 > ffff88021a3efe00 3655949445 C Bi:8:005:2 0 416 =3D 4e434d48 0c003000 a0= 010c00 49505300 10000000 1c007a01 00000000 4500017a ffff88021a3efe00 3655949491 S Bi:8:005:2 -115 16384 < ffff88021a3ef500 3656103498 S Bo:8:005:1 -115 4096 =3D 4e434d48 0c00360= 0 00100c00 49505300 10000000 b8007a01 00000000 00000000 ffff88021a3ef500 3656103779 C Bo:8:005:1 0 4096 > ffff8802041af540 3657229210 C Bi:8:005:2 0 416 =3D 4e434d48 0c003100 a0= 010c00 49505300 10000000 1c007a01 00000000 4500017a ffff8802041af540 3657229251 S Bi:8:005:2 -115 16384 < ffff8802041af240 3659438084 C Bi:8:005:2 -104 0 ffff8802041af9c0 3659438159 C Bi:8:005:2 -104 0 ffff88021a3efc80 3659438206 C Bi:8:005:2 -104 0 Bj=C3=B8rn