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SergeyKostrov
Valued Contributor II
65 Views

Feature Request: How much time was spent waiting for I/O requests (related to paging file) during processing of large data sets

This is a Feature Request ( actually suggested by Jim ):

How much time was spent waiting for I/O requests ( related to paging file ) during processing.

Note: We have a discussion on Intel C++ Compiler Forum ( http://software.intel.com/en-us/forums/topic/401303 ) related to processing of very large data sets exceeding size of Physical Memory ( in 3x - 5x ). Or, may be such functionality is already available in Intel PCM?

 

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5 Replies
Peter_W_Intel
Employee
65 Views

This is a long story in your issue discussed in Compiler Forum...thank you.

1. If you use lightweight-hotspots (now called advanced-hotspots in U10/U11) and enable "context switches" before collecting data. Change "Hardware Event Sample Counts" as viewpoint in bottom-up report, there is a column named "Wait Time". Wait-time could be caused by many reasons, such as io-wait (File operations, Page walks, Wait message, etc), or thread suspending, etc.

2. If you want to identify issue caused by page walks - suggest to use hardware PMU events, for example:

DTLB_LOAD_MISSES, DTLB_STORE_MISSES ; they are supported in SandyBridge processors

You can use DTLB_STORE_MISSES.WALK_DURATION to measure Cycles of busy during page walks

SergeyKostrov
Valued Contributor II
65 Views

>>1. If you use lightweight-hotspots (now called advanced-hotspots in U10/U11) and enable "context switches" before collecting data. >>Change "Hardware Event Sample Counts" as viewpoint in bottom-up report, there is a column named "Wait Time". Wait-time >>could be caused by many reasons, such as io-wait (File operations, Page walks, Wait message, etc), or thread suspending, etc... I'll take a look. Thanks, Peter.
Bernard
Black Belt
65 Views

Hi Peter

is the Wait Time setting global(system-wide) or it can be charged against some thread(s)

Thanks in advance

Peter_W_Intel
Employee
65 Views

Hi iliyapolak,

All Wait Time data will be charged on functions, these data can be categorized into threads for view.

Regards, Peter

Bernard
Black Belt
65 Views

Thank you Peter

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