From: Jason Gunthorpe <jgg@ziepe.ca>
To: Aruna Ramakrishna <aruna.ramakrishna@oracle.com>
Cc: Praveen Kumar Kannoju <praveen.kannoju@oracle.com>,
leon@kernel.org, dledford@redhat.com, linux-rdma@vger.kernel.org,
linux-kernel@vger.kernel.org,
Rajesh Sivaramasubramaniom
<rajesh.sivaramasubramaniom@oracle.com>,
Rama Nichanamatlu <rama.nichanamatlu@oracle.com>,
Jeffery Yoder <jeffery.yoder@oracle.com>
Subject: Re: [PATCH v2] IB/mlx5: Reduce max order of memory allocated for xlt update
Date: Thu, 25 Mar 2021 11:39:28 -0300 [thread overview]
Message-ID: <20210325143928.GM2710221@ziepe.ca> (raw)
In-Reply-To: <0DFF7518-8818-445B-94AC-8EB2096446BE@oracle.com>
On Tue, Mar 23, 2021 at 09:27:38PM -0700, Aruna Ramakrishna wrote:
> > Do you have benchmarks that show the performance of the high order
> > pages is not relavent? I'm a bit surprised to hear that
> >
>
> I guess my point was more to the effect that an order-8 alloc will
> fail more often than not, in this flow. For instance, when we were
> debugging the latency spikes here, this was the typical buddyinfo
> output on that system:
>
> Node 0, zone DMA 0 1 1 2 3 0 1 0 1 1 3
> Node 0, zone DMA32 7 7 7 6 10 2 6 7 6 2 306
> Node 0, zone Normal 3390 51354 17574 6556 1586 26 2 1 0 0 0
> Node 1, zone Normal 11519 23315 23306 9738 73 2 0 1 0 0 0
>
> I think this level of fragmentation is pretty normal on long running
> systems. Here, in the reg_mr flow, the first try (order-8) alloc
> will probably fail 9 times out of 10 (esp. after the addition of
> GFP_NORETRY flag), and then as fallback, the code tries to allocate
> a lower order, and if that too fails, it allocates a page. I think
> it makes sense to just avoid trying an order-8 alloc here.
But a system like this won't get THPs either, so I'm not sure it is
relevant. The function was designed as it is to consume a "THP" if it
is available.
Jason
next prev parent reply other threads:[~2021-03-25 14:40 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-16 13:09 [PATCH v2] IB/mlx5: Reduce max order of memory allocated for xlt update Praveen Kumar Kannoju
2021-03-23 13:42 ` Praveen Kannoju
2021-03-23 16:07 ` Jason Gunthorpe
[not found] ` <80966C8E-341B-4F5D-9DCA-C7D82AB084D5@oracle.com>
2021-03-23 23:13 ` Jason Gunthorpe
2021-03-24 4:27 ` Aruna Ramakrishna
2021-03-25 14:39 ` Jason Gunthorpe [this message]
2021-03-31 17:53 ` Jason Gunthorpe
2021-04-01 15:56 ` Praveen Kannoju
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