From: Ilias Apalodimas <ilias.apalodimas@linaro.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>,
netdev@vger.kernel.org, lirongqing@baidu.com,
linyunsheng@huawei.com, Saeed Mahameed <saeedm@mellanox.com>,
peterz@infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [net-next v4 PATCH] page_pool: handle page recycle for NUMA_NO_NODE condition
Date: Thu, 19 Dec 2019 17:28:41 +0200 [thread overview]
Message-ID: <20191219152841.GA6889@apalos.home> (raw)
In-Reply-To: <20191219145206.GE26945@dhcp22.suse.cz>
On Thu, Dec 19, 2019 at 03:52:06PM +0100, Michal Hocko wrote:
> On Thu 19-12-19 14:35:35, Jesper Dangaard Brouer wrote:
> > On Thu, 19 Dec 2019 13:09:25 +0100
> > Michal Hocko <mhocko@kernel.org> wrote:
> >
> > > On Wed 18-12-19 09:01:35, Jesper Dangaard Brouer wrote:
> > > [...]
> > > > For the NUMA_NO_NODE case, when a NIC IRQ is moved to another NUMA
> > > > node, then ptr_ring will be emptied in 65 (PP_ALLOC_CACHE_REFILL+1)
> > > > chunks per allocation and allocation fall-through to the real
> > > > page-allocator with the new nid derived from numa_mem_id(). We accept
> > > > that transitioning the alloc cache doesn't happen immediately.
> >
> > Oh, I just realized that the drivers usually refill several RX
> > packet-pages at once, this means that this is called N times, meaning
> > during a NUMA change this will result in N * 65 pages returned.
> >
> >
> > > Could you explain what is the expected semantic of NUMA_NO_NODE in this
> > > case? Does it imply always the preferred locality? See my other email[1] to
> > > this matter.
> >
> > I do think we want NUMA_NO_NODE to mean preferred locality.
>
Why? wouldn't it be clearer if it meant "this is not NUMA AWARE"?
The way i see it iyou have drivers that sit on specific SoCs,
like the ti one, or the netsec one can declare 'NUMA_NO_NODE' since they
know beforehand what hardware they'll be sitting on.
On PCI/USB pluggable interfaces mlx5 example should be followed.
> I obviously have no saying here because I am not really familiar with
> the users of this API but I would note that if there is such an implicit
> assumption then you make it impossible to use the numa agnostic page
> pool allocator (aka fast reallocation). This might be not important here
> but future extension would be harder (you can still hack it around aka
> NUMA_REALLY_NO_NODE). My experience tells me that people are quite
> creative and usually require (or worse assume) semantics that you
> thought were not useful.
>
> That being said, if the NUMA_NO_NODE really should have a special
> locality meaning then document it explicitly at least.
Agree, if we treat it like this we have to document it somehow
> --
> Michal Hocko
> SUSE Labs
Thanks
/Ilias
next prev parent reply other threads:[~2019-12-19 15:28 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-17 23:17 [net-next v3 PATCH] page_pool: handle page recycle for NUMA_NO_NODE condition Jesper Dangaard Brouer
2019-12-18 7:44 ` Jesper Dangaard Brouer
2019-12-18 8:01 ` [net-next v4 " Jesper Dangaard Brouer
2019-12-18 14:27 ` 答复: " Li,Rongqing
2019-12-19 12:00 ` Jesper Dangaard Brouer
2019-12-19 12:47 ` 答复: " Li,Rongqing
2019-12-19 1:52 ` Yunsheng Lin
2019-12-19 12:15 ` Jesper Dangaard Brouer
2019-12-19 12:09 ` Michal Hocko
2019-12-19 13:35 ` Jesper Dangaard Brouer
2019-12-19 14:52 ` Michal Hocko
2019-12-19 15:28 ` Ilias Apalodimas [this message]
2019-12-19 14:20 ` [net-next v5 " Jesper Dangaard Brouer
2019-12-20 10:23 ` Ilias Apalodimas
2019-12-20 10:41 ` Jesper Dangaard Brouer
2019-12-20 10:49 ` Ilias Apalodimas
2019-12-20 15:22 ` Jesper Dangaard Brouer
2019-12-20 16:06 ` Ilias Apalodimas
2019-12-23 7:57 ` Ilias Apalodimas
2019-12-23 16:52 ` Jesper Dangaard Brouer
2019-12-23 22:10 ` Saeed Mahameed
2019-12-24 9:34 ` Ilias Apalodimas
2019-12-24 7:41 ` Ilias Apalodimas
2019-12-20 21:27 ` Saeed Mahameed
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