From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f43.google.com (mail-wg0-f43.google.com [74.125.82.43]) by dpdk.org (Postfix) with ESMTP id 6EC422A9 for ; Fri, 7 Nov 2014 15:21:46 +0100 (CET) Received: by mail-wg0-f43.google.com with SMTP id y10so3907796wgg.16 for ; Fri, 07 Nov 2014 06:31:18 -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=aTHS6x5TR95gg4/lDXltvmX0RpRmOI2gOOjmiLH9Y/M=; b=o1++sbPXYGfiEH3fJzQm30Nq4Y6ecg5qSpbgkPgwYGdhToXHPbNxPkx9BANAztKG/e VkMQGoxrjdHTNj/fNfCybpsVf3KJjV0/XIiCShDl+hBT2HsTD6DSJGLK93dN2CyKE3Cn flxXJWZCy+WgCFhw1Dtp1BliK2vCvJu1f8CeQYeTJ9/9v3RQfNUBmaLe6iH4Oa1DCc7p qeWinmbHbPfec6NnQ8BoFu7CxNTE8Tg5n5CrzwHHvOAEarJ/nxNj9GM05S1TE5FLzXE1 qGWcPqZmDxYrNVv06vxeWH+DBj81XCoM7P7AHIvRd2l9FOd+bqPu8e5p5NxR4CgrfW16 U1lw== MIME-Version: 1.0 X-Received: by 10.180.95.201 with SMTP id dm9mr5486712wib.27.1415370678481; Fri, 07 Nov 2014 06:31:18 -0800 (PST) Received: by 10.27.86.144 with HTTP; Fri, 7 Nov 2014 06:31:18 -0800 (PST) In-Reply-To: <20141107135303.GB12092@bricha3-MOBL3> 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> <20141107094521.GB4628@bricha3-MOBL3> <20141107135303.GB12092@bricha3-MOBL3> Date: Fri, 7 Nov 2014 16:31:18 +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: Fri, 07 Nov 2014 14:21:46 -0000 Hi Bruce, Pls have a quick look at the diff to see if this is exactly what you mean about the bitmask. I just wrote it without even compiling, just to express the idea. So it may leave some places unpatched. If this is agreed, I will make a decent test to verify it before sending the patch for RFC. diff --git a/lib/librte_distributor/rte_distributor.c b/lib/librte_distributor/rte_di index 585ff88..d606bcf 100644 --- a/lib/librte_distributor/rte_distributor.c +++ b/lib/librte_distributor/rte_distributor.c @@ -92,6 +92,8 @@ struct rte_distributor { unsigned num_workers; /**< Number of workers polling */ uint32_t in_flight_tags[RTE_MAX_LCORE]; + uint32_t in_flight_bitmask; + struct rte_distributor_backlog backlog[RTE_MAX_LCORE]; union rte_distributor_buffer bufs[RTE_MAX_LCORE]; @@ -188,6 +190,7 @@ static inline void handle_worker_shutdown(struct rte_distributor *d, unsigned wkr) { d->in_flight_tags[wkr] =3D 0; + d->in_flight_mask &=3D ~(1 << wkr); d->bufs[wkr].bufptr64 =3D 0; if (unlikely(d->backlog[wkr].count !=3D 0)) { /* On return of a packet, we need to move the @@ -241,6 +244,7 @@ process_returns(struct rte_distributor *d) else { d->bufs[wkr].bufptr64 =3D RTE_DISTRIB_GET_B= UF; d->in_flight_tags[wkr] =3D 0; + d->in_flight_mask &=3D ~(1 << wkr); } oldbuf =3D data >> RTE_DISTRIB_FLAG_BITS; } else if (data & RTE_DISTRIB_RETURN_BUF) { @@ -282,12 +286,13 @@ rte_distributor_process(struct rte_distributor *d, next_mb =3D mbufs[next_idx++]; next_value =3D (((int64_t)(uintptr_t)next_mb) << RTE_DISTRIB_FLAG_BITS); - new_tag =3D (next_mb->hash.rss | 1); + new_tag =3D next_mb->hash.rss; uint32_t match =3D 0; unsigned i; for (i =3D 0; i < d->num_workers; i++) - match |=3D (!(d->in_flight_tags[i] ^ new_ta= g) + match |=3D (((!(d->in_flight_tags[i] ^ new_tag)) & + (d->in_flight_bitmask >> i)= ) << i); if (match) { @@ -309,6 +314,7 @@ rte_distributor_process(struct rte_distributor *d, else { d->bufs[wkr].bufptr64 =3D next_value; d->in_flight_tags[wkr] =3D new_tag; + d->in_flight_bitmask |=3D 1 << wkr; next_mb =3D NULL; } oldbuf =3D data >> RTE_DISTRIB_FLAG_BITS; On Fri, Nov 7, 2014 at 3:53 PM, Bruce Richardson wrote: > On Fri, Nov 07, 2014 at 02:38:13PM +0200, jigsaw wrote: > > Hi Bruce, > > > > >> If a tag value of zero is ever passed in, then it will start matchi= ng > > against cores which are not doing any processing. > > > > Yes, this is true according to current bookkeeping of inflight tags. > > > > But if the slot in in_flight_tags is not a uint32_t but a struct which > has > > a filed as indication of "on/off", and also with corresponding changes = in > > looking for a matched tag, then the need for 1 bit mask can be > eliminated. > > Of course this change requires a little bit more, O(n), memory space an= d > > costs O(n) more branch misses. But the benefit is a more free interface > to > > user app. > > > > This is just another trade-off. Since I am in need of such freedom, I a= m > > more interested in the free use of 32bits. > > If you do implement such a change, I would suggest you simply add a bitma= sk > to the distributor indicating valid workers. Then when we do the check > for tag matches, we just need an extra "and" instruction to eliminate > invalid > workers from the match. > > /Bruce > > > > > thx & > > rgds, > > -qinglai > > > > > > On Fri, Nov 7, 2014 at 11:45 AM, Bruce Richardson < > > bruce.richardson@intel.com> wrote: > > > > > On Thu, Nov 06, 2014 at 09:52:25PM +0200, jigsaw wrote: > > > > 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 h= e > is > > > > doing. Of course this shall be clearly documented in the > comment/doxgen. > > > > > > > > > > > > thx & > > > > rgds, > > > > -qinglai > > > > > > I don't believe that will work. If a tag value of zero is ever passed > > > in, then it will start matching against cores which are not doing any > > > processing. Then it will get queued up to get sent to those cores, an= d > so > > > never get processed. > > > We need a bit somewhere inside the tag to permanently set - though it > can > > > be configurable. > > > > > > /Bruce > > > > > > > > > > > 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 ca= n > 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 > > > way > > > > >> so as to handle this situation. > > > > >> > > > > >> It's not just in that, case, it's in any case where a pair of ta= gs > > > differ > > > > >> by > > > > >> only a single bit. I've been assuming that the tag is likely to > be a > > > hash > > > > >> value in most cases - given that it's only 32-bit - in which cas= e > it > > > just > > > > >> 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 n= ot > > > so, we > > > > >> can > > > > >> look to change which bit is set to 1. Either way, the distributo= r > 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=8E1= 1/=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 ta= g calculation > 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 > > > > >> > > > > > > > > > > > > > >