io_uring proof of concept

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io_uring proof of concept #188

Open olivierlambert opened 5 years ago

olivierlambert commented 5 years ago

[ ] getting a kernel 5.1 in dom0 @rushikeshjadhav
[ ] switching tapdisk from libaio to liburing @nraynaud
[ ] understand those changes and bench it @Wescoeur

This might be also really interesting about SMAPIv1/v3 benchmarks: especially on finding bottlenecks (are they in tapdisk or elsewhere?)

olivierlambert commented 5 years ago

@rushikeshjadhav no rush, but if you can take a look at the effort needed to include a 5.1 kernel in dom0, since we got a 4.19 in CH/XCP-ng 8.0 it might be doable.

If it's doable in a reasonable amount of time, then let's go :+1:

rushikeshjadhav commented 5 years ago

Sure. I think both XCP 7.6 and 8.0 can benefit from 5.1. Will wait for XCP-ng 8.0 ISO to become available.

olivierlambert commented 5 years ago

This ISO will land tomorrow on Tuesday, stay tuned :)

olivierlambert commented 5 years ago

@rushikeshjadhav ISO is now available: https://updates.xcp-ng.org/isos/8.0/xcp-ng-8.0.0-beta.iso

In the meantime, @nraynaud will start to take a look soon on tapdisk thing and what's io_uring

Few interesting links:

Intro: http://kernel.dk/io_uring.pdf
Deep dive: https://lwn.net/Articles/776703/ (maybe a bit outdated but still)

rushikeshjadhav commented 5 years ago

I saw the kernel changes and it seems they removed functions that blktap was dependent on. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/block/blk-core.c?h=v5.0.18&id=a1ce35fa49852db60fc6e268038530be533c5b15

So to let blktap work with 5.1, it would need extra work on kernel side driver. @nraynaud What do you think?

Meanwhile, 4.19 and its upgrades are being tracked at https://github.com/rushikeshjadhav/kernel-4.19

olivierlambert commented 5 years ago

@rushikeshjadhav so if I understand correctly, as soon you have a 5.1 kernel running in the dom0, blktap will cease to work? I'll be interested to try it as soon you got something :)

rushikeshjadhav commented 5 years ago

5.1 will not compile with blktap module without adapting the changes to block/blk-core.c, I'm going through some changes but it will take time.

Let me make a 5.1 without blktap module. Dom0 can work but you won't be able to run VMs though.

olivierlambert commented 5 years ago

Sure, fine enough for me, the main objective is to see how hard it is to get the kernel, then we'll see what to adapt :+1: