From: Sagi Grimberg <sagi@grimberg.me>
To: Max Gurtovoy <maxg@mellanox.com>,
James Smart <jsmart2021@gmail.com>,
linux-nvme@lists.infradead.org
Cc: "Ewan D . Milne" <emilne@redhat.com>
Subject: Re: [PATCH] nvme-fc: set max_segments to lldd max value
Date: Mon, 20 Jul 2020 12:56:42 -0700 [thread overview]
Message-ID: <ed9ba851-9e0e-f5ba-8dbd-1be3d46ac3d5@grimberg.me> (raw)
In-Reply-To: <75927cec-e607-0293-47d3-f8b6141425f0@mellanox.com>
>> Currently the FC transport is set max_hw_sectors based on the lldds
>> max sgl segment count. However, the block queue max segments is
>> set based on the controller's max_segments count, which the transport
>> does not set. As such, the lldd is receiving sgl lists that are
>> exceeding its max segment count.
>>
>> Set the controller max segment count and derive max_hw_sectors from
>> the max segment count.
>>
>> Signed-off-by: James Smart <jsmart2021@gmail.com>
>> Reviewed-by: Ewan D. Milne <emilne@redhat.com>
>> CC: Max Gurtovoy <maxg@mellanox.com>
>>
>> ---
>> Looks like the setting of max_segments has been missing from all
>> fabric transports for a while. Rdma had a fixup (ff13c1b87c97) from
>> Max last fall that corrected this. But tcp and fc were still lacking.
>> Copying Max to look at tcp.
>
> The TCP stack is not limiting the IO size, I guess because of the fact
> it's a streaming protocol.
>
> So I don't see a bug in the tcp driver but we can consider limiting the
> IO size if it will improve performance in some cases.
>
> BTW, AFAIK the iscsi TCP acts the same.
>
> Sagi,
>
> do you see some benefits we can get by limiting the mdts for tcp ?
Not really...
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next prev parent reply other threads:[~2020-07-20 19:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-14 19:03 [PATCH] nvme-fc: set max_segments to lldd max value James Smart
2020-07-15 9:04 ` Max Gurtovoy
2020-07-20 19:56 ` Sagi Grimberg [this message]
2020-07-20 21:11 ` Himanshu Madhani
2020-07-26 15:43 ` Christoph Hellwig
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