netdev - Re: [PATCH v2 0/4] open/accept directly into io

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Date:   Sun, 15 Aug 2021 09:12:19 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Josh Triplett <josh@...htriplett.org>
Cc:     Pavel Begunkov <asml.silence@...il.com>, io-uring@...r.kernel.org,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, Stefan Metzmacher <metze@...ba.org>
Subject: Re: [PATCH v2 0/4] open/accept directly into io_uring fixed file
 table

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