Re: [osv-dev] GDB stub

[Glauber Costa]

On Mon., Feb. 8, 2021, 3:00 a.m. Nadav Har'El,  wrote:

> On Wed, Feb 3, 2021 at 1:18 AM Waldek Kozaczuk 
> wrote:
>
>> Currently, it is only possible to connect from gdb to a running instance
>> of OSv on QEMU. But ideally, it would be nice to have a gdb stub in OSv
>> that would let one connect from gdb to OSv running on any hypervisor.
>>
>> Per this fragment of this Wiki -
>> https://github.com/cloudius-systems/osv/wiki/Debugging-OSv
>>
>> *"The fact that our gdb support works with the unit of cpus, not OSV
>> threads, makes it convenient to debug OSV itself, but less convenient to
>> debug application code running inside OSV. Particularly problematic is
>> single stepping support which isn’t currently supported well: The problem
>> is that when you try to look at a single OSV thread (see the next section),
>> a single-step operation (“s” or “n”) makes one step inside the vcpu, not
>> the osv thread*, and this step might include switching to a different
>> thread. One way to work around this problem is to compile OSV with
>> preemption disabled (not recommended, but can be a convenient trick in some
>> debugging situations). *A better approach would have been to include a
>> gdb stub into OSV itself, to allow gdb to see OSV threads directly and
>> single-step them. We’ve made some progress in implementing such a stub, but
>> it isn’t ready for prime-time yet.*"
>>
>> it looks like somebody may have implemented an initial version of the gdb
>> stub. Is there a working patch of it somewhere?
>>
>
> I have a vague recollection - it was many years ago - that Glauber (CCed)
> was the one who tried doing it.
> Glauber, if it was you, do you remember what you tried?
> If it wasn't you, sorry for the spam :-)
>

I don't think it was me. I have no memory of ever doing this.

But no need to be sorry, it's good to hear from you!

>
>
>> Regards,
>> Waldek
>>
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>> 
>> .
>>
>

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Re: ScyllaDB on OSv?

[Glauber Costa]

On Fri, Aug 12, 2016 at 3:26 PM, Roman Shaposhnik 
wrote:

> On Fri, Aug 12, 2016 at 10:33 AM, Avi Kivity  wrote:
> > On 08/12/2016 08:23 PM, Waldek Kozaczuk wrote:
> >>
> >> Given that ScyllaDB uses seastar that can run on OSv is it possible to
> run
> >> ScyllaDB on OSv? I have not found anything on scyllaDB site ?
> >>
> >> If no are there any plans do make it possible? If yes would there be any
> >> advantage of running scylladb on top of OSV performance-wise?
> >
> >
> > Right now OSv lacks a good aio-enabled filesystem.  ZFS is designed to
> > provide clever caching and file management tools (ARC, snapshots) while
> > ScyllaDB wants to do its own caching and DMA file data directly from disk
> > using AIO.
>
> What's your recommended FS on Linux?
>

XFS. We don't technically support any of the others.

In reality, you can run anywhere that io_submit and friends are available,
but you will not get good performance out of it.


>
> Thanks,
> Roman.
>
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