Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Miklos Szeredi]

On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
>
> Hi!
>
> > > At first, I thought that the proposed system call is capable of
> > > reading *multiple* small files using a single system call - which
> > > would help increase HDD/SSD queue utilization and increase IOPS (I/O
> > > operations per second) - but that isn't the case and the proposed
> > > system call can read just a single file.
> >
> > If you want to do this for multple files, use io_ring, that's what it
> > was designed for.  I think Jens was going to be adding support for the
> > open/read/close pattern to it as well, after some other more pressing
> > features/fixes were finished.
>
> What about... just using io_uring for single file, too? I'm pretty
> sure it can be wrapped in a library that is simple to use, avoiding
> need for new syscall.

Just wondering:  is there a plan to add strace support to io_uring?
And I don't just mean the syscalls associated with io_uring, but
tracing the ring itself.

I think that's quite important as io_uring becomes mainstream.

Thanks,
Miklos

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Pavel Begunkov]

On 14/07/2020 11:07, Miklos Szeredi wrote:
> On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
>>
>> Hi!
>>
>>>> At first, I thought that the proposed system call is capable of
>>>> reading *multiple* small files using a single system call - which
>>>> would help increase HDD/SSD queue utilization and increase IOPS (I/O
>>>> operations per second) - but that isn't the case and the proposed
>>>> system call can read just a single file.
>>>
>>> If you want to do this for multple files, use io_ring, that's what it
>>> was designed for.  I think Jens was going to be adding support for the
>>> open/read/close pattern to it as well, after some other more pressing
>>> features/fixes were finished.
>>
>> What about... just using io_uring for single file, too? I'm pretty
>> sure it can be wrapped in a library that is simple to use, avoiding
>> need for new syscall.
> 
> Just wondering:  is there a plan to add strace support to io_uring?
> And I don't just mean the syscalls associated with io_uring, but
> tracing the ring itself.

What kind of support do you mean? io_uring is asynchronous in nature
with all intrinsic tracing/debugging/etc. problems of such APIs.
And there are a lot of handy trace points, are those not enough?

Though, this can be an interesting project to rethink how async
APIs are worked with.

> 
> I think that's quite important as io_uring becomes mainstream.

-- 
Pavel Begunkov

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Miklos Szeredi]

On Tue, Jul 14, 2020 at 1:36 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 14/07/2020 11:07, Miklos Szeredi wrote:
> > On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
> >>
> >> Hi!
> >>
> >>>> At first, I thought that the proposed system call is capable of
> >>>> reading *multiple* small files using a single system call - which
> >>>> would help increase HDD/SSD queue utilization and increase IOPS (I/O
> >>>> operations per second) - but that isn't the case and the proposed
> >>>> system call can read just a single file.
> >>>
> >>> If you want to do this for multple files, use io_ring, that's what it
> >>> was designed for.  I think Jens was going to be adding support for the
> >>> open/read/close pattern to it as well, after some other more pressing
> >>> features/fixes were finished.
> >>
> >> What about... just using io_uring for single file, too? I'm pretty
> >> sure it can be wrapped in a library that is simple to use, avoiding
> >> need for new syscall.
> >
> > Just wondering:  is there a plan to add strace support to io_uring?
> > And I don't just mean the syscalls associated with io_uring, but
> > tracing the ring itself.
>
> What kind of support do you mean? io_uring is asynchronous in nature
> with all intrinsic tracing/debugging/etc. problems of such APIs.
> And there are a lot of handy trace points, are those not enough?
>
> Though, this can be an interesting project to rethink how async
> APIs are worked with.

Yeah, it's an interesting problem.  The uring has the same events, as
far as I understand, that are recorded in a multithreaded strace
output (syscall entry, syscall exit); nothing more is needed.

I do think this needs to be integrated into strace(1), otherwise the
usefulness of that tool (which I think is *very* high) would go down
drastically as io_uring usage goes up.

Thanks,
Miklos

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Pavel Begunkov]

On 14/07/2020 14:55, Miklos Szeredi wrote:
> On Tue, Jul 14, 2020 at 1:36 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>
>> On 14/07/2020 11:07, Miklos Szeredi wrote:
>>> On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
>>>>
>>>> Hi!
>>>>
>>>>>> At first, I thought that the proposed system call is capable of
>>>>>> reading *multiple* small files using a single system call - which
>>>>>> would help increase HDD/SSD queue utilization and increase IOPS (I/O
>>>>>> operations per second) - but that isn't the case and the proposed
>>>>>> system call can read just a single file.
>>>>>
>>>>> If you want to do this for multple files, use io_ring, that's what it
>>>>> was designed for.  I think Jens was going to be adding support for the
>>>>> open/read/close pattern to it as well, after some other more pressing
>>>>> features/fixes were finished.
>>>>
>>>> What about... just using io_uring for single file, too? I'm pretty
>>>> sure it can be wrapped in a library that is simple to use, avoiding
>>>> need for new syscall.
>>>
>>> Just wondering:  is there a plan to add strace support to io_uring?
>>> And I don't just mean the syscalls associated with io_uring, but
>>> tracing the ring itself.
>>
>> What kind of support do you mean? io_uring is asynchronous in nature
>> with all intrinsic tracing/debugging/etc. problems of such APIs.
>> And there are a lot of handy trace points, are those not enough?
>>
>> Though, this can be an interesting project to rethink how async
>> APIs are worked with.
> 
> Yeah, it's an interesting problem.  The uring has the same events, as
> far as I understand, that are recorded in a multithreaded strace
> output (syscall entry, syscall exit); nothing more is needed> 
> I do think this needs to be integrated into strace(1), otherwise the
> usefulness of that tool (which I think is *very* high) would go down
> drastically as io_uring usage goes up.

Not touching the topic of usefulness of strace + io_uring, but I'd rather
have a tool that solves a problem, than a problem that created and honed
for a tool.

-- 
Pavel Begunkov

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Miklos Szeredi]

On Wed, Jul 15, 2020 at 10:33 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>
> On 14/07/2020 14:55, Miklos Szeredi wrote:
> > On Tue, Jul 14, 2020 at 1:36 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
> >>
> >> On 14/07/2020 11:07, Miklos Szeredi wrote:
> >>> On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
> >>>>
> >>>> Hi!
> >>>>
> >>>>>> At first, I thought that the proposed system call is capable of
> >>>>>> reading *multiple* small files using a single system call - which
> >>>>>> would help increase HDD/SSD queue utilization and increase IOPS (I/O
> >>>>>> operations per second) - but that isn't the case and the proposed
> >>>>>> system call can read just a single file.
> >>>>>
> >>>>> If you want to do this for multple files, use io_ring, that's what it
> >>>>> was designed for.  I think Jens was going to be adding support for the
> >>>>> open/read/close pattern to it as well, after some other more pressing
> >>>>> features/fixes were finished.
> >>>>
> >>>> What about... just using io_uring for single file, too? I'm pretty
> >>>> sure it can be wrapped in a library that is simple to use, avoiding
> >>>> need for new syscall.
> >>>
> >>> Just wondering:  is there a plan to add strace support to io_uring?
> >>> And I don't just mean the syscalls associated with io_uring, but
> >>> tracing the ring itself.
> >>
> >> What kind of support do you mean? io_uring is asynchronous in nature
> >> with all intrinsic tracing/debugging/etc. problems of such APIs.
> >> And there are a lot of handy trace points, are those not enough?
> >>
> >> Though, this can be an interesting project to rethink how async
> >> APIs are worked with.
> >
> > Yeah, it's an interesting problem.  The uring has the same events, as
> > far as I understand, that are recorded in a multithreaded strace
> > output (syscall entry, syscall exit); nothing more is needed>
> > I do think this needs to be integrated into strace(1), otherwise the
> > usefulness of that tool (which I think is *very* high) would go down
> > drastically as io_uring usage goes up.
>
> Not touching the topic of usefulness of strace + io_uring, but I'd rather
> have a tool that solves a problem, than a problem that created and honed
> for a tool.

Sorry, I'm not getting the metaphor.  Can you please elaborate?

Thanks,
Miklos

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Pavel Begunkov]

On 15/07/2020 11:41, Miklos Szeredi wrote:
> On Wed, Jul 15, 2020 at 10:33 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>
>> On 14/07/2020 14:55, Miklos Szeredi wrote:
>>> On Tue, Jul 14, 2020 at 1:36 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>>
>>>> On 14/07/2020 11:07, Miklos Szeredi wrote:
>>>>> On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
>>>>>>
>>>>>> Hi!
>>>>>>
>>>>>>>> At first, I thought that the proposed system call is capable of
>>>>>>>> reading *multiple* small files using a single system call - which
>>>>>>>> would help increase HDD/SSD queue utilization and increase IOPS (I/O
>>>>>>>> operations per second) - but that isn't the case and the proposed
>>>>>>>> system call can read just a single file.
>>>>>>>
>>>>>>> If you want to do this for multple files, use io_ring, that's what it
>>>>>>> was designed for.  I think Jens was going to be adding support for the
>>>>>>> open/read/close pattern to it as well, after some other more pressing
>>>>>>> features/fixes were finished.
>>>>>>
>>>>>> What about... just using io_uring for single file, too? I'm pretty
>>>>>> sure it can be wrapped in a library that is simple to use, avoiding
>>>>>> need for new syscall.
>>>>>
>>>>> Just wondering:  is there a plan to add strace support to io_uring?
>>>>> And I don't just mean the syscalls associated with io_uring, but
>>>>> tracing the ring itself.
>>>>
>>>> What kind of support do you mean? io_uring is asynchronous in nature
>>>> with all intrinsic tracing/debugging/etc. problems of such APIs.
>>>> And there are a lot of handy trace points, are those not enough?
>>>>
>>>> Though, this can be an interesting project to rethink how async
>>>> APIs are worked with.
>>>
>>> Yeah, it's an interesting problem.  The uring has the same events, as
>>> far as I understand, that are recorded in a multithreaded strace
>>> output (syscall entry, syscall exit); nothing more is needed>
>>> I do think this needs to be integrated into strace(1), otherwise the
>>> usefulness of that tool (which I think is *very* high) would go down
>>> drastically as io_uring usage goes up.
>>
>> Not touching the topic of usefulness of strace + io_uring, but I'd rather
>> have a tool that solves a problem, than a problem that created and honed
>> for a tool.
> 
> Sorry, I'm not getting the metaphor.  Can you please elaborate?

Sure, I mean _if_ there are tools that conceptually suit better, I'd
prefer to work with them, then trying to shove a new and possibly alien
infrastructure into strace.

But my knowledge of strace is very limited, so can't tell whether that's
the case. E.g. can it utilise static trace points?

-- 
Pavel Begunkov

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Pavel Begunkov]

On 15/07/2020 11:49, Pavel Begunkov wrote:
> On 15/07/2020 11:41, Miklos Szeredi wrote:
>> On Wed, Jul 15, 2020 at 10:33 AM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>
>>> On 14/07/2020 14:55, Miklos Szeredi wrote:
>>>> On Tue, Jul 14, 2020 at 1:36 PM Pavel Begunkov <asml.silence@gmail.com> wrote:
>>>>>
>>>>> On 14/07/2020 11:07, Miklos Szeredi wrote:
>>>>>> On Tue, Jul 14, 2020 at 8:51 AM Pavel Machek <pavel@denx.de> wrote:
>>>>>>>
>>>>>>> Hi!
>>>>>>>
>>>>>>>>> At first, I thought that the proposed system call is capable of
>>>>>>>>> reading *multiple* small files using a single system call - which
>>>>>>>>> would help increase HDD/SSD queue utilization and increase IOPS (I/O
>>>>>>>>> operations per second) - but that isn't the case and the proposed
>>>>>>>>> system call can read just a single file.
>>>>>>>>
>>>>>>>> If you want to do this for multple files, use io_ring, that's what it
>>>>>>>> was designed for.  I think Jens was going to be adding support for the
>>>>>>>> open/read/close pattern to it as well, after some other more pressing
>>>>>>>> features/fixes were finished.
>>>>>>>
>>>>>>> What about... just using io_uring for single file, too? I'm pretty
>>>>>>> sure it can be wrapped in a library that is simple to use, avoiding
>>>>>>> need for new syscall.
>>>>>>
>>>>>> Just wondering:  is there a plan to add strace support to io_uring?
>>>>>> And I don't just mean the syscalls associated with io_uring, but
>>>>>> tracing the ring itself.
>>>>>
>>>>> What kind of support do you mean? io_uring is asynchronous in nature
>>>>> with all intrinsic tracing/debugging/etc. problems of such APIs.
>>>>> And there are a lot of handy trace points, are those not enough?
>>>>>
>>>>> Though, this can be an interesting project to rethink how async
>>>>> APIs are worked with.
>>>>
>>>> Yeah, it's an interesting problem.  The uring has the same events, as
>>>> far as I understand, that are recorded in a multithreaded strace
>>>> output (syscall entry, syscall exit); nothing more is needed>
>>>> I do think this needs to be integrated into strace(1), otherwise the
>>>> usefulness of that tool (which I think is *very* high) would go down
>>>> drastically as io_uring usage goes up.
>>>
>>> Not touching the topic of usefulness of strace + io_uring, but I'd rather
>>> have a tool that solves a problem, than a problem that created and honed
>>> for a tool.
>>
>> Sorry, I'm not getting the metaphor.  Can you please elaborate?
> 
> Sure, I mean _if_ there are tools that conceptually suit better, I'd
> prefer to work with them, then trying to shove a new and possibly alien
> infrastructure into strace.
> 
> But my knowledge of strace is very limited, so can't tell whether that's
> the case. E.g. can it utilise static trace points?

I think, if you're going to push this idea, we should start a new thread
CC'ing strace devs.
	
-- 
Pavel Begunkov

Re: [PATCH 0/3] readfile(2): a new syscall to make open/read/close faster

[Miklos Szeredi]

On Wed, Jul 15, 2020 at 11:02 AM Pavel Begunkov <asml.silence@gmail.com> wrote:

> I think, if you're going to push this idea, we should start a new thread
> CC'ing strace devs.

Makes sense.   I've pruned the Cc list, so here's the link for reference:

https://lore.kernel.org/linux-fsdevel/CAJfpegu3EwbBFTSJiPhm7eMyTK2MzijLUp1gcboOo3meMF_+Qg@mail.gmail.com/T/#u

Thanks,
Miklos