On 2/12/2018 2:11 PM, Jerin Jacob wrote: > -----Original Message----- >> Date: Mon, 12 Feb 2018 14:02:17 +0000 >> From: Matan Azrad <[email protected]> >> To: Jerin Jacob <[email protected]> >> CC: "[email protected]" <[email protected]>, "[email protected]" >> <[email protected]>, "[email protected]" <[email protected]>, Thomas >> Monjalon <[email protected]>, Konstantin Ananyev >> <[email protected]>, Pavan Nikhilesh >> <[email protected]> >> Subject: RE: [dpdk-dev] [PATCH v3] ethdev: fix ethdev data alignment >> >> >> >> From: Jerin Jacob, Sent: Monday, February 12, 2018 3:51 PM >>> -----Original Message----- >>>> Date: Mon, 12 Feb 2018 13:44:54 +0000 >>>> From: Matan Azrad <[email protected]> >>>> To: Jerin Jacob <[email protected]>, "[email protected]" >>>> <[email protected]> >>>> CC: "[email protected]" <[email protected]>, "[email protected]" >>>> <[email protected]>, Thomas Monjalon <[email protected]>, >>> Konstantin >>>> Ananyev <[email protected]>, Pavan Nikhilesh >>>> <[email protected]> >>>> Subject: RE: [dpdk-dev] [PATCH v3] ethdev: fix ethdev data alignment >>>> >>>> Hi Jerin >>>> >>>> From: Jerin Jacob [mailto:[email protected]] >>>>> The struct rte_eth_dev_data is used in ethdev fastpath routines and >>>>> it not aligned to cache line size. This patch fixes the ethdev data >>> alignment. >>>>> >>>>> The alignment was broken from the "first public release" changeset >>>>> where ethdev data address was aligned only to the first port. >>>>> Remaining ports alignment was defined by the size of the struct >>>>> (rte_eth_dev_data). This scheme is not guaranteed to be cache line >>>>> aligned all the time. >>>>> >>>>> "ethdev: add port ownership" change set introduced a >>>>> rte_eth_dev_shared_data container for port ownership change, This >>>>> resulted in rte_eth_dev->data memory for the first port also as >>>>> cache unaligned. >>>>> >>>>> Added a compiler alignment attribute to make sure rte_eth_dev->data >>>>> always cache aligned so that CPU/compiler >>>>> 1) Avoid sharing the element with another cache line >>>>> 2) Can load/store the elements in struct rte_eth_dev_data as >>>>> naturally aligned. >>>>> >>>>> Some platform like thunderX could see performance regression of 1% >>>>> at >>>>> "ethdev: add port ownership" change set with >>>>> 1 port/1 queue l3fwd application and this patch fixes that regression. >>>>> >>>>> example command: >>>>> sudo ./examples/l3fwd/build/l3fwd -c 0xff00 -- -p 0x1 --config="(0,0,9)" >>>>> >>>>> Fixes: af75078fece3 ("first public release") >>>>> Fixes: 5b7ba31148a8 ("ethdev: add port ownership") >>>> >>>> I don't think you need the add the 5b7ba31148a8 fix line. >>>> Maybe think about it in the next way: >>>> Is your fix can stay as a same fix before the port ownership feature >>> addition? >>>> If yes, You are not fixing it. >>> >>> I don't think so. 5b7ba31148a8 breaking the first port alignment case(as >>> mentioned in the commit log clearly). >>> First port alignment was correct prior to 5b7ba31148a8 change set >>> >>> Do you agree? >> >> No. >> The root cause of the issue this fix is fixing, is that the structure is not >> aligned, it is not relevant to port ownership. >> The port ownership just exposes it. > > My point is simple. First port alignment was correct prior to 5b7ba31148a8 > change set. > it is broken from there.
+1 for this logic, adding fixes line makes sense for me. > > It is minor thing. I let, ethdev maintainer to decide what to added in Fixes > on apply. >
