Re: [PATCH v2 0/4] open/accept directly into io_uring fixed file table

From: Jens Axboe <axboe@kernel.dk>
To: Josh Triplett <josh@joshtriplett.org>
Cc: Pavel Begunkov <asml.silence@gmail.com>,
	io-uring@vger.kernel.org,
	"David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	Stefan Metzmacher <metze@samba.org>
Subject: Re: [PATCH v2 0/4] open/accept directly into io_uring fixed file table
Date: Sun, 15 Aug 2021 09:12:19 -0600	[thread overview]
Message-ID: <e404f278-bfca-0cff-92b7-6d4cdc93ff60@kernel.dk> (raw)
In-Reply-To: <a2bd1600-5649-c4be-d2a9-79c89bae774a@kernel.dk>

On 8/15/21 9:05 AM, Jens Axboe wrote:
> On 8/14/21 9:42 PM, Josh Triplett wrote:
>> On Sat, Aug 14, 2021 at 05:03:44PM -0600, Jens Axboe wrote:
>>> What's the plan in terms of limiting the amount of direct descriptors
>>> (for lack of a better word)? That seems like an important aspect that
>>> should get sorted out upfront.
>> [...]
>>> Maybe we have a way to size the direct table, which will consume entries
>>> from the same pool that the regular file table does? That would then
>>> work both ways, and could potentially just be done dynamically similarly
>>> to how we expand the regular file table when we exceed its current size.
>>
>> I think we'll want a way to size the direct table regardless, so that
>> it's pre-allocated and doesn't need to be resized when an index is used.
> 
> But how do you size it then? I can see this being used into the hundreds
> of thousands of fds easily, and right now the table is just an array
> (though split into segments, avoiding huge allocs).

I guess that will just naturally follow by registering the empty set of
a given size initially. So should not actually be a problem...

-- 
Jens Axboe