On 1/11/19 11:34 AM, Jens Axboe wrote:
> On 1/11/19 11:19 AM, Martin K. Petersen wrote:
>>
>> Jens,
>>
>>> +struct io_uring_sqe {
>>> + __u8 opcode;
>>> + __u8 flags;
>>> + __u16 ioprio;
>>> + __s32 fd;
>>> + __u64 off;
>>> + union {
>>> + void *addr;
>>> + __u64 __pad;
>>> + };
>>> + __u32 len;
>>> + union {
>>> + __kernel_rwf_t rw_flags;
>>> + __u32 __resv;
>>> + };
>>> +};
>>
>> A bit tongue in cheek and yet somewhat serious: While I'm super excited
>> about the 4 x 64 bitness of the sqe, where does the integrity buffer go?
>> Or the 128-bit KV store key. How do we extend this interface beyond the
>> flags?
>
> For integrity buffers, how about we stash them on the side? The newer
> series has an extra system call, io_uring_register(), which is currently
> used for registering files and buffers for IO on the side. You could
> trivially tie an integrity buffer to an sqe through that.
>
> For KV, I thint that's an actually interesting use case (sorry,
> integrity), and we might just want to bite the bullet and extend the sqe
> to full 64 bytes. We're currently at 48 bytes, which leaves us with 16
> bytes of space for KV, and other use cases.
I bit the bullet and bumped the size. 64 bytes is a nicer size in terms
of cachelines anyway, and I really doubt that 48 vs 64 bytes makes a
size consumption problem for anyone.
The buf_index is only used for the fixed buffers, which means that we have
16 bytes / 128 bits that we can grab for things like KV.
--
Jens Axboe
