Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: 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>
References: <cover.1628871893.git.asml.silence@gmail.com>
 <YRbBYCn29B+kgZcy@localhost> <bcb6f253-41d6-6e0f-5b4b-ea1e02a105bc@gmail.com>
 <5cf40313-d151-9d10-3ebd-967eb2f53b1f@kernel.dk> <YRiNGTL2Dp/7vNzt@localhost>
 <a2bd1600-5649-c4be-d2a9-79c89bae774a@kernel.dk>
Message-ID: <e404f278-bfca-0cff-92b7-6d4cdc93ff60@kernel.dk>
Date:   Sun, 15 Aug 2021 09:12:19 -0600
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <a2bd1600-5649-c4be-d2a9-79c89bae774a@kernel.dk>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

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