[parsec-users] Fwd: Swaptions communication

abhisekpan at gmail.com abhisekpan at gmail.com
Fri Nov 8 16:28:15 EST 2013


Hi SIddharth,

I do not think the code was executed in kernel mode, we saw some sharing in
GEMS-ruby even when we were filtering the kernel-mode accesses. That would
mean these were happening inside the standard library implementation, but
probably not inside system calls. Also we were using the old simics-GEMS
framework, and kernel mode accesses are visible to ruby. Unfortunately, I
am not very familiar with the GEM5 set-up.

Best,
Abhisek


On Fri, Nov 8, 2013 at 12:18 PM, Siddharth Nilakantan <sid.nil at gmail.com>wrote:

> Hi all,
>
> Very sorry for the late response. I didn't get an explicit reply in my
> mail inbox, but rather a digest version of daily mails and I missed your
> responses.
>
> Kishore,
>
> I think Abhisek answered your question. I saw communication between all
> threads. The paper I linked to, has a thread communication pattern in
> Figure 5. Take a look at that.
>
> Abhisek,
>
> Thanks for the info. How did you narrow in on the function names that the
> addresses were accessed under? Am I correct in assuming that these library
> calls are executed in kernel mode? The simulation framework I am using does
> not have visibility into what happens in the kernel. I wonder how Gem5's SE
> mode would handle such calls. Would it do the appropriate locking.
>
> Sid
>
>
> On 31 October 2013 12:00, <parsec-users-request at lists.cs.princeton.edu>wrote:
>
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>> Today's Topics:
>>
>>    1. Fwd: Swaptions communication (Siddharth Nilakantan)
>>    2. Re: Fwd: Swaptions communication (kishore kumar)
>>    3. Re: Fwd: Swaptions communication (abhisekpan at gmail.com)
>>
>>
>> ---------- Forwarded message ----------
>> From: Siddharth Nilakantan <sid.nil at gmail.com>
>> To: parsec-users at lists.cs.princeton.edu
>> Cc:
>> Date: Wed, 30 Oct 2013 19:56:32 -0400
>> Subject: [parsec-users] Fwd: Swaptions communication
>> Hi All,
>>
>> I've been running some multi-core simulations with Swaptions and I've
>> noticed that there is thread communication. From looking at the source code
>> for swaptions, there should be no communication, as all threads work on
>> independent data. Hence, the lack of synchronization primitives as well.
>>
>> I ran simmedium (32 swaptions), 16 threads and 8 cores. It should divide
>> up evenly and there should be no communication at all. These guys also find
>> that swaptions has communication:
>> http://parsec.cs.princeton.edu/publications/barrow-williams09comm.pdf
>>
>> Can anyone explain to me why Swaptions exhibits communication?
>>
>> Regards,
>> Siddharth Nilakantan
>>
>>
>>
>> ---------- Forwarded message ----------
>> From: kishore kumar <kishoreguptaos at gmail.com>
>> To: PARSEC Users <parsec-users at lists.cs.princeton.edu>
>> Cc:
>> Date: Wed, 30 Oct 2013 17:09:28 -0700
>> Subject: Re: [parsec-users] Fwd: Swaptions communication
>> Hi Siddharth,
>>
>> How do you find that there is a communication between threads? Which data?
>>
>> Best,
>> Kishore Kumar Pusukuri
>> http://www.cs.ucr.edu/~kishore
>>
>>
>> On Wed, Oct 30, 2013 at 4:56 PM, Siddharth Nilakantan <sid.nil at gmail.com>wrote:
>>
>>> Hi All,
>>>
>>> I've been running some multi-core simulations with Swaptions and I've
>>> noticed that there is thread communication. From looking at the source code
>>> for swaptions, there should be no communication, as all threads work on
>>> independent data. Hence, the lack of synchronization primitives as well.
>>>
>>> I ran simmedium (32 swaptions), 16 threads and 8 cores. It should divide
>>> up evenly and there should be no communication at all. These guys also find
>>> that swaptions has communication:
>>> http://parsec.cs.princeton.edu/publications/barrow-williams09comm.pdf
>>>
>>> Can anyone explain to me why Swaptions exhibits communication?
>>>
>>> Regards,
>>> Siddharth Nilakantan
>>>
>>>
>>> _______________________________________________
>>> parsec-users mailing list
>>> parsec-users at lists.cs.princeton.edu
>>> https://lists.cs.princeton.edu/mailman/listinfo/parsec-users
>>>
>>>
>>
>>
>> ---------- Forwarded message ----------
>> From: "abhisekpan at gmail.com" <abhisekpan at gmail.com>
>> To: PARSEC Users <parsec-users at lists.cs.princeton.edu>
>> Cc:
>> Date: Wed, 30 Oct 2013 20:30:08 -0400
>> Subject: Re: [parsec-users] Fwd: Swaptions communication
>> Hi Siddharth,
>>
>> As far as I remember, we saw that the swaption threads use some floating
>> point libraries (sqrt calls maybe) which do not always declare per-thread
>> data structures, and hence some data is shared by all threads. I am sorry I
>> can not be more precise at this point, but you are right in that the code
>> does not explicitly communicate, and the communication happens through some
>> library calls. Hope this helps you in some little way!
>>
>> The way I found this was through the following: dis-assemble the code
>> (static build), run it in simics, and then compare the logical addresses
>> which are accessed by more than one cores.
>>
>>  Thanks,
>> Abhisek
>>
>>
>> On Wed, Oct 30, 2013 at 7:56 PM, Siddharth Nilakantan <sid.nil at gmail.com>wrote:
>>
>>> Hi All,
>>>
>>> I've been running some multi-core simulations with Swaptions and I've
>>> noticed that there is thread communication. From looking at the source code
>>> for swaptions, there should be no communication, as all threads work on
>>> independent data. Hence, the lack of synchronization primitives as well.
>>>
>>> I ran simmedium (32 swaptions), 16 threads and 8 cores. It should divide
>>> up evenly and there should be no communication at all. These guys also find
>>> that swaptions has communication:
>>> http://parsec.cs.princeton.edu/publications/barrow-williams09comm.pdf
>>>
>>> Can anyone explain to me why Swaptions exhibits communication?
>>>
>>> Regards,
>>> Siddharth Nilakantan
>>>
>>>
>>> _______________________________________________
>>> parsec-users mailing list
>>> parsec-users at lists.cs.princeton.edu
>>> https://lists.cs.princeton.edu/mailman/listinfo/parsec-users
>>>
>>>
>>
>>
>> _______________________________________________
>> parsec-users mailing list
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>>
>>
>


-- 
Abhisek
Live Long and Prosper
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