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From: Thomas Monjalon <thomas@monjalon.net>
To: "Burakov, Anatoly" <anatoly.burakov@intel.com>,
	"You, KaisenX" <kaisenx.you@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>,
	"Zhou, YidingX" <yidingx.zhou@intel.com>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>,
	"Matz, Olivier" <olivier.matz@6wind.com>,
	"ferruh.yigit@amd.com" <ferruh.yigit@amd.com>,
	"zhoumin@loongson.cn" <zhoumin@loongson.cn>,
	"stable@dpdk.org" <stable@dpdk.org>,
	bruce.richardson@intel.com, jerinj@marvell.com
Subject: Re: [PATCH v5] enhance NUMA affinity heuristic
Date: Fri, 03 Mar 2023 15:07:14 +0100	[thread overview]
Message-ID: <4598779.O6GEm4j1yj@thomas> (raw)
In-Reply-To: <SJ0PR11MB67659D4EA0E7569A4C16841DE1A09@SJ0PR11MB6765.namprd11.prod.outlook.com>

I'm not comfortable with this patch.

First, there is no comment in the code which helps to understand the logic.
Second, I'm afraid changing the value of the per-core variable _socket_id
may have an impact on some applications.


16/02/2023 03:50, You, KaisenX:
> From: Burakov, Anatoly <anatoly.burakov@intel.com>
> > On 2/1/2023 12:20 PM, Kaisen You wrote:
> > > Trying to allocate memory on the first detected numa node has less
> > > chance to find some memory actually available rather than on the main
> > > lcore numa node (especially when the DPDK application is started only
> > > on one numa node).
> > >
> > > Fixes: 705356f0811f ("eal: simplify control thread creation")
> > > Fixes: bb0bd346d5c1 ("eal: suggest using --lcores option")
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: David Marchand <david.marchand@redhat.com>
> > > Signed-off-by: Kaisen You <kaisenx.you@intel.com>
> > > ---
> > > Changes since v4:
> > > - mod the patch title,
> > >
> > > Changes since v3:
> > > - add the assignment of socket_id in thread initialization,
> > >
> > > Changes since v2:
> > > - add uncommitted local change and fix compilation,
> > >
> > > Changes since v1:
> > > - accomodate for configurations with main lcore running on multiples
> > >    physical cores belonging to different numa,
> > > ---
> > >   lib/eal/common/eal_common_thread.c | 1 +
> > >   lib/eal/common/malloc_heap.c       | 4 ++++
> > >   2 files changed, 5 insertions(+)
> > >
> > > diff --git a/lib/eal/common/eal_common_thread.c
> > > b/lib/eal/common/eal_common_thread.c
> > > index 38d83a6885..21bff971f8 100644
> > > --- a/lib/eal/common/eal_common_thread.c
> > > +++ b/lib/eal/common/eal_common_thread.c
> > > @@ -251,6 +251,7 @@ static void *ctrl_thread_init(void *arg)
> > >   	void *routine_arg = params->arg;
> > >
> > >   	__rte_thread_init(rte_lcore_id(), cpuset);
> > > +	RTE_PER_LCORE(_socket_id) = SOCKET_ID_ANY;
> > >   	params->ret = rte_thread_set_affinity_by_id(rte_thread_self(),
> > cpuset);
> > >   	if (params->ret != 0) {
> > >   		__atomic_store_n(&params->ctrl_thread_status,
> > > diff --git a/lib/eal/common/malloc_heap.c
> > > b/lib/eal/common/malloc_heap.c index d7c410b786..3ee19aee15 100644
> > > --- a/lib/eal/common/malloc_heap.c
> > > +++ b/lib/eal/common/malloc_heap.c
> > > @@ -717,6 +717,10 @@ malloc_get_numa_socket(void)
> > >   			return socket_id;
> > >   	}
> > >
> > > +	socket_id = rte_lcore_to_socket_id(rte_get_main_lcore());
> > > +	if (socket_id != (unsigned int)SOCKET_ID_ANY)
> > > +		return socket_id;
> > > +
> > >   	return rte_socket_id_by_idx(0);
> > >   }
> > >
> > 
> > I may be lacking context, but I don't quite get the suggested change.
> >  From what I understand, the original has to do with assigning lcore cpusets in
> > such a way that an lcore ends up having two socket ID's (because it's been
> > assigned to CPU's on different sockets). Why is this allowed in the first place?
> > It seems like a user error to me, as it breaks many of the fundamental
> > assumptions DPDK makes.
> > 
> In a dual socket system, if all used cores are in socket 1 and the NIC is in socket 1, 
> no memory is allocated for socket 0. This is to optimize memory consumption.
> 
> I agree with you. If the startup parameters can ensure that both sockets 
> allocate memory, there will be no problem.
> However, due to the different CPU topologies of different systems, 
> It is difficult for users to ensure that the startup parameter contains two cpu nodes.
> 
> > I'm fine with using main lcore socket for control threads, I just don't think the
> > `socket_id != SOCKET_ID_ANY` thing should be checked here, because it
> > apparently tries to compensate for a problem with cpuset of the main thread,
> > which shouldn't have happened to begin with.
> > 
> This issue has been explained in detail in the discussion of the patch v1 version. 
> I will forward the previous email to you. The content of the email will also better 
> let you know the purpose of submitting this patch.




  reply	other threads:[~2023-03-03 14:07 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-21 10:48 [PATCH] malloc: " David Marchand
2022-12-21 11:16 ` Bruce Richardson
2022-12-21 13:50   ` Ferruh Yigit
2022-12-21 14:57 ` David Marchand
2022-12-27  9:00   ` zhoumin
2023-01-03 10:56     ` David Marchand
2023-01-03 10:58 ` [PATCH v2] " David Marchand
2023-01-03 13:32 ` [PATCH v3] " David Marchand
2023-01-31  3:23   ` You, KaisenX
2023-01-31 15:05 ` [PATCH v4] net/iavf:enhance " Kaisen You
2023-01-31 16:05   ` Thomas Monjalon
2023-02-01  5:32     ` You, KaisenX
2023-02-01 12:20 ` [PATCH v5] enhance " Kaisen You
2023-02-01 10:52   ` Jiale, SongX
2023-02-15 14:22   ` Burakov, Anatoly
2023-02-15 14:47     ` Burakov, Anatoly
2023-02-16  2:50     ` You, KaisenX
2023-03-03 14:07       ` Thomas Monjalon [this message]
2023-03-09  1:58         ` You, KaisenX
2023-04-13  0:56           ` You, KaisenX
2023-04-19 12:16             ` Thomas Monjalon
2023-04-21  2:34               ` You, KaisenX
2023-04-21  8:12                 ` Thomas Monjalon
2023-04-23  6:52                   ` You, KaisenX
2023-04-23  8:57                     ` You, KaisenX
2023-04-23 13:19                       ` Thomas Monjalon
2023-04-25  5:16   ` [PATCH v6] " Kaisen You
2023-04-27  6:57     ` Thomas Monjalon
2023-05-16  5:19       ` You, KaisenX
2023-05-23  2:50     ` [PATCH v7] " Kaisen You
2023-05-23 10:44       ` Burakov, Anatoly
2023-05-26  6:44         ` You, KaisenX
2023-05-23 12:45       ` Burakov, Anatoly
2023-05-26  6:50       ` [PATCH v8] " Kaisen You
2023-05-26  8:45       ` Kaisen You
2023-05-26 14:44         ` Burakov, Anatoly
2023-05-26 17:50           ` Stephen Hemminger
2023-05-29 10:37             ` Burakov, Anatoly
2023-06-01 14:42         ` David Marchand
2023-06-06 14:04           ` Thomas Monjalon
2023-06-12  9:36           ` Burakov, Anatoly

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