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* how long wait_for_completion_interruptible_timeout() blocks
@ 2019-06-19 17:16 Subhashini Rao Beerisetty
  2019-06-20  6:07 ` anish singh
  0 siblings, 1 reply; 3+ messages in thread
From: Subhashini Rao Beerisetty @ 2019-06-19 17:16 UTC (permalink / raw)
  To: kernelnewbies

Hi All,

I’ve two Linux systems, I tried to measure how long
wait_for_completion_interruptible_timeout() blocked after completion
is signaled by complete() call. I noticed two different results in
both systems.

In one system I noticed this duration in between 10 to 60 micro
seconds, where as in other system  it is in between 20 to 500 micro
seconds. I’d like to know what factors can affect this latency? Also,
is there any solution to reduce this latency?


Thanks,

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: how long wait_for_completion_interruptible_timeout() blocks
  2019-06-19 17:16 how long wait_for_completion_interruptible_timeout() blocks Subhashini Rao Beerisetty
@ 2019-06-20  6:07 ` anish singh
  2019-06-20  7:28   ` Subhashini Rao Beerisetty
  0 siblings, 1 reply; 3+ messages in thread
From: anish singh @ 2019-06-20  6:07 UTC (permalink / raw)
  To: Subhashini Rao Beerisetty; +Cc: kernelnewbies

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On Wed, Jun 19, 2019 at 10:47 PM Subhashini Rao Beerisetty <
subhashbeerisetty@gmail.com> wrote:

> Hi All,
>
> I’ve two Linux systems, I tried to measure how long
> wait_for_completion_interruptible_timeout() blocked after completion
> is signaled by complete() call. I noticed two different results in
> both systems.
>
> In one system I noticed this duration in between 10 to 60 micro
> seconds, where as in other system  it is in between 20 to 500 micro
> seconds. I’d like to know what factors can affect this latency? Also,
> is there any solution to reduce this latency?


This is a problem which is fixed by RT Linux patches.
It is taking time as Linux is not RTOS and scheduler took time to put your
task in running state which is expected and depends on many factors: such
as load, interrupts and so on.

>
>
>
> Thanks,
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies@kernelnewbies.org
> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>

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<div><br></div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jun 19, 2019 at 10:47 PM Subhashini Rao Beerisetty &lt;<a href="mailto:subhashbeerisetty@gmail.com">subhashbeerisetty@gmail.com</a>&gt; wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi All,<br>
<br>
I’ve two Linux systems, I tried to measure how long<br>
wait_for_completion_interruptible_timeout() blocked after completion<br>
is signaled by complete() call. I noticed two different results in<br>
both systems.<br>
<br>
In one system I noticed this duration in between 10 to 60 micro<br>
seconds, where as in other system  it is in between 20 to 500 micro<br>
seconds. I’d like to know what factors can affect this latency? Also,<br>
is there any solution to reduce this latency?</blockquote><div dir="auto"><br></div><div dir="auto">This is a problem which is fixed by RT Linux patches.</div><div dir="auto">It is taking time as Linux is not RTOS and scheduler took time to put your task in running state which is expected and depends on many factors: such as load, interrupts and so on.</div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
<br>
<br>
Thanks,<br>
<br>
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</blockquote></div></div>

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^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: how long wait_for_completion_interruptible_timeout() blocks
  2019-06-20  6:07 ` anish singh
@ 2019-06-20  7:28   ` Subhashini Rao Beerisetty
  0 siblings, 0 replies; 3+ messages in thread
From: Subhashini Rao Beerisetty @ 2019-06-20  7:28 UTC (permalink / raw)
  To: anish singh; +Cc: kernelnewbies

On Thu, Jun 20, 2019 at 11:38 AM anish singh
<anish198519851985@gmail.com> wrote:
>
>
>
> On Wed, Jun 19, 2019 at 10:47 PM Subhashini Rao Beerisetty <subhashbeerisetty@gmail.com> wrote:
>>
>> Hi All,
>>
>> I’ve two Linux systems, I tried to measure how long
>> wait_for_completion_interruptible_timeout() blocked after completion
>> is signaled by complete() call. I noticed two different results in
>> both systems.
>>
>> In one system I noticed this duration in between 10 to 60 micro
>> seconds, where as in other system  it is in between 20 to 500 micro
>> seconds. I’d like to know what factors can affect this latency? Also,
>> is there any solution to reduce this latency?
>
>
> This is a problem which is fixed by RT Linux patches.
Can these patches be applied to Linux kernel source? If so can you
please give more information on this... where to find these patches?

> It is taking time as Linux is not RTOS and scheduler took time to put your task in running state which is expected and depends on many factors: such as load, interrupts and so on.
>>
>>
>>
>>
>> Thanks,
>>
>> _______________________________________________
>> Kernelnewbies mailing list
>> Kernelnewbies@kernelnewbies.org
>> https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2019-06-19 17:16 how long wait_for_completion_interruptible_timeout() blocks Subhashini Rao Beerisetty
2019-06-20  6:07 ` anish singh
2019-06-20  7:28   ` Subhashini Rao Beerisetty

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