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Date:   Tue, 17 May 2022 16:35:15 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Long Li <longli@microsoft.com>
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>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH 05/12] net: mana: Set the DMA device max page size
Message-ID: <20220517193515.GN63055@ziepe.ca>
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On Tue, May 17, 2022 at 07:32:51PM +0000, Long Li wrote:
> > Subject: Re: [PATCH 05/12] net: mana: Set the DMA device max page size
> > 
> > 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.
> > 
> > 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.

As I said, it should be the size of the sge in the WQE, not the
"hardware page tables"

Jason