Paul Brook wrote:
Yes, librt is providing posix-aio, and librt coming with GNU libc uses
threads.
But if I remember correctly librt coming with RHEL uses a mix of threads
and linux kernel AIO (you can have a look to the .srpm of libc).

BTW, if everyone thinks it could be a good idea I can port block-raw.c
to use linux kernel AIO (without removing POSIX AIO support, of course)

This seems rather pointless, given a user can just use a linux-AIO librt instead.

Not at all. linux-aio is the only interface that allows you to do asynchronous fdsync which simulates a barrier which allows for an ordered queue.

I have a patch that uses linux-aio for the virtio-blk driver I'll be posting tomorrow and I'm extremely happy with the results. In recent kernels, you can use an eventfd interface along with linux-aio so that polling is unnecessary. Along with O_DIRECT and the preadv/pwritev interface, you can make a block backend in userspace that performs just as well as if it were in the kernel.

The posix-aio interface simply doesn't provide a mechanism to do these things.

Regards,

Anthony Liguori

Paul






Reply via email to