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Message-ID: <028fd6f1-6fc2-6e8d-3de0-71c2b8f6b754@grimberg.me>
Date: Tue, 20 Jun 2023 16:00:31 +0300
From: Sagi Grimberg <sagi@...mberg.me>
To: David Howells <dhowells@...hat.com>,
Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: netdev@...r.kernel.org,
Alexander Duyck <alexander.duyck@...il.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
David Ahern <dsahern@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Jens Axboe <axboe@...nel.dk>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, Keith Busch <kbusch@...nel.org>,
Jens Axboe <axboe@...com>, Christoph Hellwig <hch@....de>,
Chaitanya Kulkarni <kch@...dia.com>,
linux-nvme@...ts.infradead.org
Subject: Re: [PATCH net-next v2 10/17] nvme: Use sendmsg(MSG_SPLICE_PAGES)
rather then sendpage
>>> struct bio_vec bvec;
>>> struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES | ... };
>>>
>>> ..
>>>
>>> bvec_set_virt
>>> iov_iter_bvec
>>> sock_sendmsg
>>>
>>> is a frequent pattern. Does it make sense to define a wrapper? Same
>>> for bvec_set_page.
>>
>> I dunno. I'm trying to move towards aggregating multiple pages in a bvec
>> before calling sendmsg if possible rather than doing it one page at a
>> time,
>> but it's easier and more obvious in some places than others.
>
> That would be great to do, but nvme needs to calculate a data digest
> and doing that in a separate scan of the payload is not very cache
> friendly...
>
> There is also the fact that the payload may be sent in portions
> asynchronously driven by how the controller wants to accept them,
> so there is some complexity there.
>
> But worth looking at for sure.
>
> The patch looks good to me, taking it to run some tests
> (from sendpage-3-frag branch in your kernel.org tree correct?)
>
> For now, you can add:
> Reviewed-by: Sagi Grimberg <sagi@...mberg.me>
Patches seem to hold up.
Tested-by: Sagi Grimberg <sagi@...mberg.me>
However if possible, can you please split nvme/host and nvme/target
changes? We try to separate host side and target side changes in the
same patch.
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