From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f41.google.com (mail-wg0-f41.google.com [74.125.82.41]) by dpdk.org (Postfix) with ESMTP id 20FE92E89 for ; Thu, 6 Nov 2014 20:42:57 +0100 (CET) Received: by mail-wg0-f41.google.com with SMTP id k14so2089970wgh.0 for ; Thu, 06 Nov 2014 11:52:25 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=vuZccqbcvJb3iBBv2diT2mInWECPd9zrnXlvt8P0Mrw=; b=bZvJjLLudQwbK9HQtNIRYIUCaekrnpSS3Mg+jeDEipaMlle3ndc09dUCBhtw5obGVm HZPfUPOEdEdj3NLrY9FkEQl+lyfNuRWxSBne0YLXFiHpPHlUV+EEn5y05oO8+nawx5dE mbEY7Z9X+4e8D42EYP6GHp2sVum/+18CWYRddFmeF2KInfKIDTRDo/t7UeZ2m5VU8ppx 07ABlE5AHGufw+Nwy74x4Vu6AI+D/ggofapKcgw5oqbdEQ3r3h9TXCD8gf1vrJynwi8S 2HPCCiJ33TmzKQLTdlgGvAz/kILt9magSx0CkP4M1Svv+tncrAYPNEM963PBJWA+2vnO u18Q== MIME-Version: 1.0 X-Received: by 10.194.63.79 with SMTP id e15mr9125034wjs.79.1415303545776; Thu, 06 Nov 2014 11:52:25 -0800 (PST) Received: by 10.27.86.144 with HTTP; Thu, 6 Nov 2014 11:52:25 -0800 (PST) In-Reply-To: References: <1415194237-1219-1-git-send-email-jigsaw@gmail.com> <20141106092228.GA3056@bricha3-MOBL3> <9190772.1rnKUO3oNV@xps13> <545b6b74.a96db40a.26af.ffffe7fb@mx.google.com> <20141106135951.GB7252@bricha3-MOBL3> Date: Thu, 6 Nov 2014 21:52:25 +0200 Message-ID: From: jigsaw To: Bruce Richardson Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.15 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] =?utf-8?b?562U5aSNOiAgW1BBVENIXSBBZGQgdXNlciBkZWZpbmVk?= =?utf-8?q?_tag_calculation_callback_tolibrte=5Fdistributor=2E?= X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 06 Nov 2014 19:42:57 -0000 Hi Bruce, Actually IMHO it is good to leave the freedom to user to decide how to interpret the tag value, i.e. remove the OR 1 bit. If the tag value is zero, then we assume the programmer know what he is doing. Of course this shall be clearly documented in the comment/doxgen. thx & rgds, -qinglai On Thu, Nov 6, 2014 at 8:01 PM, jigsaw wrote: > Hi Bruce, > > In my use case, unfortunately the tag is not hash. And the tag can be on > either low or high bits, depending on configuration. > I wonder if it is possible to let the user to decide which bit to mask, > i.e. to add another param to rte_distributor_create to define the mask. > > thx & > rgds, > -qinglai > > On Thu, Nov 6, 2014 at 3:59 PM, Bruce Richardson < > bruce.richardson@intel.com> wrote: > >> On Thu, Nov 06, 2014 at 02:36:09PM +0200, Qinglai Xiao wrote: >> > Hi Bruce, >> > >> > There is a subtle case in which tag values are 2 and 3, respectively. >> Then these two tags cannot be distinguished. There should be a better wa= y >> so as to handle this situation. >> >> It's not just in that, case, it's in any case where a pair of tags diffe= r >> by >> only a single bit. I've been assuming that the tag is likely to be a has= h >> value in most cases - given that it's only 32-bit - in which case it jus= t >> doesn't >> matter which bit we chose to permanently set to 1, but if there are >> scenarios >> where it's likely that the low bits are used but the high ones not so, w= e >> can >> look to change which bit is set to 1. Either way, the distributor just >> uses a >> 31-bit tag rather than a 32-bit one. >> >> /Bruce >> >> > >> > thx & >> > rgds >> > -qinglai >> > >> > -----=E5=8E=9F=E5=A7=8B=E9=82=AE=E4=BB=B6----- >> > =E5=8F=91=E4=BB=B6=E4=BA=BA: "Thomas Monjalon" >> > =E5=8F=91=E9=80=81=E6=97=B6=E9=97=B4: =E2=80=8E2014/=E2=80=8E11/=E2=80= =8E6 12:36 >> > =E6=94=B6=E4=BB=B6=E4=BA=BA: "Bruce Richardson" >> > =E6=8A=84=E9=80=81: "dev@dpdk.org" ; "jigsaw" >> > =E4=B8=BB=E9=A2=98: Re: [dpdk-dev] [PATCH] Add user defined tag calcul= ation callback >> tolibrte_distributor. >> > >> > 2014-11-06 09:22, Bruce Richardson: >> > > On Wed, Nov 05, 2014 at 07:24:13PM +0200, jigsaw wrote: >> > > > >> http://dpdk.org/browse/dpdk/tree/lib/librte_distributor/rte_distributor.= c#n285 >> > > > >> > > > new_tag =3D (next_mb->hash.rss | 1); >> > > > >> > > > Why the logical OR is needed? >> > > >> > > That's needed to ensure that we never track a tag with an actual >> value of zero. >> > > We instead always force the low bit to be 1, so that we can use zero >> as an >> > > "empty" value. >> > >> > Bruce, could you check how this code may be better commented please? >> > This discussion shows that the distributor library probably needs more >> > explanations in the code or doxygen. >> > >> > Thanks >> > -- >> > Thomas >> > >