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: Tue, 21 Jul 2020 05:15:55 +0000 Message-ID: <CY4PR1101MB2310C59B19F5CD8C2E1D60FFF8780@CY4PR1101MB2310.namprd11.prod.outlook.com> (raw) In-Reply-To: <BL0PR11MB2931813A8EE2601B3EB9DD85EB7B0@BL0PR11MB2931.namprd11.prod.outlook.com> 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. > 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:[~2020-07-21 5:16 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 [this message] 2020-07-21 21:16 ` Dumitrescu, Cristian 2020-07-22 2:16 ` Xu, Ting 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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