From: "Xu, Ting" <ting.xu@intel.com> To: "Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>, "dev@dpdk.org" <dev@dpdk.org> Cc: "stable@dpdk.org" <stable@dpdk.org> Subject: Re: [dpdk-dev] [PATCH v3] lib/table: fix cache alignment issue Date: Wed, 22 Jul 2020 02:16:26 +0000 Message-ID: <CY4PR1101MB2310222519FAEFB4BFAE7319F8790@CY4PR1101MB2310.namprd11.prod.outlook.com> (raw) In-Reply-To: <BYAPR11MB2935CB2AA722EA1C8D1B2386EB780@BYAPR11MB2935.namprd11.prod.outlook.com> Hi, Cristian, > -----Original Message----- > From: Dumitrescu, Cristian <cristian.dumitrescu@intel.com> > Sent: Wednesday, July 22, 2020 5:17 AM > To: Xu, Ting <ting.xu@intel.com>; dev@dpdk.org > Cc: stable@dpdk.org > Subject: RE: [PATCH v3] lib/table: fix cache alignment issue > > > > > -----Original Message----- > > From: Xu, Ting <ting.xu@intel.com> > > Sent: Tuesday, July 21, 2020 6:16 AM > > To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>; dev@dpdk.org > > Cc: stable@dpdk.org > > Subject: RE: [PATCH v3] lib/table: fix cache alignment issue > > > > Hi, Cristian > > > > > -----Original Message----- > > > From: Dumitrescu, Cristian <cristian.dumitrescu@intel.com> > > > Sent: Monday, July 20, 2020 10:38 PM > > > To: Xu, Ting <ting.xu@intel.com>; dev@dpdk.org > > > Cc: stable@dpdk.org > > > Subject: RE: [PATCH v3] lib/table: fix cache alignment issue > > > > > > > > > > > > > -----Original Message----- > > > > From: Xu, Ting <ting.xu@intel.com> > > > > Sent: Thursday, July 9, 2020 2:48 AM > > > > To: dev@dpdk.org > > > > Cc: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>; Xu, Ting > > > > <ting.xu@intel.com>; stable@dpdk.org > > > > Subject: [PATCH v3] lib/table: fix cache alignment issue > > > > > > > > When create softnic hash table with 16 keys, it failed on 32bit > > > > environment because of the structure rte_bucket_4_16 alignment issue. > > > > Add __rte_cache_aligned to ensure correct cache align. > > > > > > > > Fixes: 8aa327214c ("table: hash") > > > > Cc: stable@dpdk.org > > > > > > > > Signed-off-by: Ting Xu <ting.xu@intel.com> > > > > > > > > --- > > > > v2->v3: Rebase > > > > v1->v2: Correct patch time > > > > --- > > > > lib/librte_table/rte_table_hash_key16.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/lib/librte_table/rte_table_hash_key16.c > > > > b/lib/librte_table/rte_table_hash_key16.c > > > > index 2cca1c924..5e1665c15 100644 > > > > --- a/lib/librte_table/rte_table_hash_key16.c > > > > +++ b/lib/librte_table/rte_table_hash_key16.c > > > > @@ -44,7 +44,7 @@ struct rte_bucket_4_16 { > > > > uint64_t key[4][2]; > > > > > > > > /* Cache line 2 */ > > > > - uint8_t data[0]; > > > > + uint8_t data[0] __rte_cache_aligned; > > > > }; > > > > > > > > struct rte_table_hash { > > > > -- > > > > 2.17.1 > > > > > > Hi Ting, > > > > > > This fix is breaking the execution for systems with cache line of > > > 128 bytes, > > as > > > typically (on 64-bit systems) this structure would be 64-byte in > > > size and adding the __rte_cache_aligned would force doubling the > > > size of this structure through padding enforced by the compiler. > > > > > > Can you please confirm this is caused by check below failing in the > > > table create function: > > > sizeof(struct rte_bucket_4_16) % 64) != 0 > > > > > > > The result of sizeof(struct rte_bucket_4_16) is 124 byte in this case, > > and this is the direct reason causing this failure. > > > > > Since all the other fields in this data structure are explicitly > > > declared as 64- > > bit > > > fields, due to the alignment rules I was expecting the compiler to > > > add a 32- > > bit > > > padding field after the "next" field, which is a pointer that would > > > only take > > 32 > > > bits on 32-bit systems. I am not sure why this did not take place in > > > your > > case, > > > any thoughts? > > > > > > > It shows that the size of the field struct rte_bucket_4_16 *next in > > struct > > rte_bucket_4_16 is only 32 bits. And there is no padding added by the > > compiler in my and the reporter's case. > > I tried to add a 32 bits pad field after the field next manually, and > > the result is correct then. > > Is it because in 32-bit system, the compiler will not extend the 32 > > bits pointer to 64 bits, since the 32 bits size has already matched the cache > line? > > > > > Not sure why we would run Soft NIC on 32-bit systems, might be > > > better to disable Soft NIC for 32-bit systems. > > > > > > > My proposed solution, which IMO provides the cleanest and most readable > way to fix / maintain this code: > > #ifdef RTE_ARCH_64 > > struct rte_bucket_4_16 { > //current definition of this struct > }; > > #else > > struct rte_bucket_4_16 { > //definition with padding fields for the 32-bit pointers to keep this > struct to a multiple of 64 bytes }; > > #endif > > We need to apply the same for 8-byte key and 32-byte key hash functions > from the same folder. > > What do you think, Ting? > Thanks for your advice. I think it makes sense. I have updated a new patch version based on this method, could you please help review? Thanks! > > To be honest, I do not know why we should run softnic on 32-bit > > system, I was just assigned this specific bug. It seems there is a > > complete test case for validation team to test softnic in 32-bit system. > > I am not sure is it OK to tell the validation team that we should > > disable softnic in 32-bit system now. Or we should fix this issue this > > time and discuss about the problem later? > > > > Thanks! > > > > > Thanks, > > > Cristian
next prev parent reply other threads:[~2020-07-22 2:16 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-16 16:27 [dpdk-dev] [PATCH v1] " Ting Xu 2020-06-17 5:43 ` [dpdk-dev] [PATCH v2] " Ting Xu 2020-07-02 8:06 ` Zhou, JunX W 2020-07-09 1:48 ` [dpdk-dev] [PATCH v3] " Ting Xu 2020-07-20 14:37 ` Dumitrescu, Cristian 2020-07-21 5:15 ` Xu, Ting 2020-07-21 21:16 ` Dumitrescu, Cristian 2020-07-22 2:16 ` Xu, Ting [this message] 2020-07-22 2:16 ` [dpdk-dev] [PATCH v4] " Ting Xu 2020-07-22 8:26 ` Dumitrescu, Cristian 2020-07-22 8:30 ` Xu, Ting 2020-07-22 8:49 ` Dumitrescu, Cristian 2020-07-22 8:48 ` Dumitrescu, Cristian 2020-07-29 12:01 ` David Marchand 2020-07-29 13:13 ` Dumitrescu, Cristian 2020-07-29 13:28 ` [dpdk-dev] [dpdk-stable] " David Marchand 2020-07-29 13:54 ` Dumitrescu, Cristian 2020-07-29 13:59 ` David Marchand 2020-07-29 14:53 ` Dumitrescu, Cristian 2020-07-30 6:57 ` Xu, Ting 2020-07-30 10:35 ` Kevin Traynor 2020-09-09 6:18 ` Xu, Ting 2020-09-15 8:03 ` David Marchand 2020-10-14 8:26 ` Xu, Ting 2020-10-14 13:53 ` [dpdk-dev] " David Marchand 2020-07-09 1:44 [dpdk-dev] [PATCH v3] " Ting Xu
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