On 11/1/24 14:42, Jens Axboe wrote:
On 11/1/24 8:34 AM, Ming Lei wrote:
On Fri, Nov 01, 2024 at 07:59:38AM -0600, Jens Axboe wrote:
On 10/31/24 8:42 PM, Ming Lei wrote:
On Fri, Nov 01, 2024 at 10:12:25AM +0800, Ming Lei wrote:
On Thu, Oct 31, 2024 at 03:22:18PM -0600, Jens Axboe wrote:
In hindsight everything is clearer, but it probably should've been known
that 8 bits of ->flags would run out sooner than later. Rather than
gobble up the last bit for a random use case, add a bit that controls
whether or not ->personality is used as a flags2 argument. If that is
the case, then there's a new IOSQE2_PERSONALITY flag that tells io_uring
which personality field to read.
While this isn't the prettiest, it does allow extending with 15 extra
flags, and retains being able to use personality with any kind of
command. The exception is uring cmd, where personality2 will overlap
with the space set aside for SQE128. If they really need that, then that
The space is the 1st `short` for uring_cmd, instead of SQE128 only.
Also it is overlapped with ->optval and ->addr3, so just wondering why not
use ->__pad2?
Another ways is to use __pad2 for sqe2_flags for non-uring_cmd, and for
uring_cmd, use its top 16 as sqe2_flags, this way does work, but it is
just a bit ugly to use.
Also IOSQE2_PERSONALITY doesn't have to be per-SQE, and it can be one
feature of IORING_FEAT_IOSQE2_PERSONALITY, that is why I thought it is
fine to take the 7th bit as SQE_GROUP now.
Not sure I follow your thinking there, can you expand?
It could be one io_uring setup flag, such as
IORING_SETUP_IOSQE2_PERSONALITY.
If this flag is set, take __pad2 as sqe2_flags, otherwise use current
way, so it doesn't have to take bit7 of sqe_flags for this purpose.
Would probably have to be a IORING_SETUP_IOSQE2_FLAGS or something in
general. And while that could work, not a huge fan of that. I think we
should retain that for when a v2 of the sqe is done, to coordinate which
version to use.
A setup flag over an sqe flag for marking IMHO would be a _much_
better approach. It doesn't take an SQE bit for nothing, you can
parse and process it in the slow setup path, enable static keys
for the hot path and so on.
--
Pavel Begunkov
