From: Sagi Grimberg <sagi@grimberg.me>
To: Hannes Reinecke <hare@suse.de>,
Chaitanya Kulkarni <chaitanyak@nvidia.com>,
Daniel Wagner <dwagner@suse.de>,
"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>
Cc: Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCH v2] nvme-tcp: send quota for nvme_tcp_send_all()
Date: Tue, 25 Oct 2022 16:46:07 +0300 [thread overview]
Message-ID: <9f40e42d-7525-5644-6773-19e3b842f7f1@grimberg.me> (raw)
In-Reply-To: <fb22c7e1-3731-f997-1896-024745082ad7@suse.de>
>>> Add a send quota in nvme_tcp_send_all() to avoid stalls when sending
>>> large amounts of requests.
>>>
>>> Cc: Hannes Reinecke <hare@suse.de>
>>> Signed-off-by: Daniel Wagner <dwagner@suse.de>
>>> ---
>>>
>>> IMO, this patch might still be a good idea to add. At least in my test
>>> setup where I only have one ethernet port it makes a big difference
>>> when accessing the system via ssh. When nvme-tcp is pushing a lot of
>>> data via the network, the ssh session is completely blocked by the
>>> storage traffic. With it, the ssh session stays responsive. >
>>
>> I'm not sure whether it is possible but is there a way to gather
>> some form of quantitative data and present it here to we all know
>> exactly which aspect is improving by this patch in context of
>> "ssd session is completely blocked" ?
>>
> Doubt that we can do it. Point is, the send code will run in a tight
> loop, making scheduling of other processes / packets really hard.
> So if you have several processes on the same interface (as here with the
> ssh connection) nvme-tcp will eat up the entire bandwidth sending its
> data, and everyone else on the line will suffer.
>
> I guess the same effect could be had by adding a 'schedule()' after each
> nvme_tcp_try_send() call.
Daniel, does adding cond_resched() make the system responsive again?
next prev parent reply other threads:[~2022-10-25 13:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-24 15:03 [PATCH v2] nvme-tcp: send quota for nvme_tcp_send_all() Daniel Wagner
2022-10-25 0:54 ` Chaitanya Kulkarni
2022-10-25 5:52 ` Daniel Wagner
2022-10-25 7:09 ` Hannes Reinecke
2022-10-25 13:46 ` Sagi Grimberg [this message]
2022-10-26 7:13 ` Daniel Wagner
2022-10-26 8:30 ` Sagi Grimberg
2022-10-26 8:39 ` Daniel Wagner
2022-10-25 6:37 ` Hannes Reinecke
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