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From:   Long Li <longli@microsoft.com>
To:     Jason Gunthorpe <jgg@ziepe.ca>
CC:     KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Leon Romanovsky <leon@kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
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        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: RE: [PATCH 05/12] net: mana: Set the DMA device max page size
Thread-Topic: [PATCH 05/12] net: mana: Set the DMA device max page size
Thread-Index: AQHYac0t/cR6HA52CUOHz8pr+lzroa0jKeeAgABLXKA=
Date:   Tue, 17 May 2022 19:32:51 +0000
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> Subject: Re: [PATCH 05/12] net: mana: Set the DMA device max page size
>=20
> On Tue, May 17, 2022 at 02:04:29AM -0700, longli@linuxonhyperv.com wrote:
> > From: Long Li <longli@microsoft.com>
> >
> > The system chooses default 64K page size if the device does not
> > specify the max page size the device can handle for DMA. This do not
> > work well when device is registering large chunk of memory in that a
> > large page size is more efficient.
> >
> > Set it to the maximum hardware supported page size.
>=20
> For RDMA devices this should be set to the largest segment size an ib_sge=
 can
> take in when posting work. It should not be the page size of MR. 2M is a =
weird
> number for that, are you sure it is right?

Yes, this is the maximum page size used in hardware page tables.

Long

>=20
> Jason