From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: "Ursulin, Tvrtko" <tvrtko.ursulin@intel.com>,
Maor Gottlieb <maorg@nvidia.com>, Christoph Hellwig <hch@lst.de>,
Gal Pressman <galpress@amazon.com>,
Bob Pearson <rpearsonhpe@gmail.com>,
Leon Romanovsky <leonro@nvidia.com>,
linux-rdma@vger.kernel.org
Subject: Re: dynamic-sg patch has broken rdma_rxe
Date: Mon, 19 Oct 2020 13:29:42 +0100 [thread overview]
Message-ID: <29ab34c2-0ca3-b3c0-6196-829e31d507c8@linux.intel.com> (raw)
In-Reply-To: <20201019121211.GC6219@nvidia.com>
On 19/10/2020 13:12, Jason Gunthorpe wrote:
> On Mon, Oct 19, 2020 at 10:50:14AM +0100, Tvrtko Ursulin wrote:
>>> overshoot the max_segment if it is not a multiple of PAGE_SIZE. Simply fix
>>> the alignment before starting and don't expose this implementation detail
>>> to the callers.
>>
>> What does not make complete sense to me is the statement that input
>> alignment requirement makes it impossible to connect to DMA layer, but then
>> the patch goes to align behind the covers anyway.
>>
>> At minimum the kerneldoc should explain that max_segment will still be
>> rounded down. But wouldn't it be better for the API to be more explicit and
>> just require aligned anyway?
>
> Why?
>
> The API is to not produce sge's with a length longer than max_segment,
> it isn't to produce sge's of exactly max_segment.
>
> Everything else is an internal detail
(Half-)pretending it is disconnected from PAGE_SIZE, when it really
isn't, isn't the most obvious API design in my view.
In other words, if you let users pass in 4097 and it just works by
rounding down to 4096, but you don't let them pass 4095, I just find
this odd.
My question was why not have callers pass in page aligned max segment
like today which makes it completely transparent.
Regards,
Tvrtko
next prev parent reply other threads:[~2020-10-19 12:29 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-13 14:33 dynamic-sg patch has broken rdma_rxe Bob Pearson
2020-10-13 16:34 ` Bob Pearson
2020-10-14 22:51 ` Jason Gunthorpe
2020-10-15 7:44 ` Maor Gottlieb
2020-10-15 11:23 ` Gal Pressman
2020-10-15 12:21 ` Maor Gottlieb
2020-10-16 0:31 ` Jason Gunthorpe
2020-10-16 7:13 ` Christoph Hellwig
[not found] ` <796ca31aed8f469c957cb850385b9d09@intel.com>
2020-10-16 11:58 ` Jason Gunthorpe
2020-10-19 9:50 ` Tvrtko Ursulin
2020-10-19 12:12 ` Jason Gunthorpe
2020-10-19 12:29 ` Tvrtko Ursulin [this message]
2020-10-19 12:48 ` Jason Gunthorpe
2020-10-20 11:37 ` Tvrtko Ursulin
2020-10-20 11:47 ` Jason Gunthorpe
2020-10-20 12:31 ` Tvrtko Ursulin
2020-10-20 12:56 ` Jason Gunthorpe
2020-10-20 13:09 ` Tvrtko Ursulin
2020-10-20 13:32 ` Jason Gunthorpe
2020-10-15 15:35 ` Bob Pearson
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