[gpfsug-discuss] gpfsug-discuss Digest, Vol 113, Issue 19

Tue Jun 22 17:26:52 BST 2021

Simon,

Thanks for the quick response and related information! We are at least at v5.0.5 so we shouldn't see much exposure to this issue then.

Thanks,

Oluwasijibomi (Siji) Saula

HPC Systems Administrator  /  Information Technology

Research 2 Building 220B / Fargo ND 58108-6050

p: 701.231.7749 / www.ndsu.edu<http://www.ndsu.edu/>

[cid:image001.gif at 01D57DE0.91C300C0]

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Today's Topics:

   1. GPFS bad at memory-mapped files? (Saula, Oluwasijibomi)
   2. Re: GPFS bad at memory-mapped files? (Simon Thompson)

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Message: 1
Date: Tue, 22 Jun 2021 15:17:16 +0000
From: "Saula, Oluwasijibomi" <oluwasijibomi.saula at ndsu.edu>
To: "gpfsug-discuss at spectrumscale.org"
        <gpfsug-discuss at spectrumscale.org>
Subject: [gpfsug-discuss] GPFS bad at memory-mapped files?
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Content-Type: text/plain; charset="windows-1252"

Hello,

While reviewing AMS software suite for installation, I noticed this remark (https://www.scm.com/doc/Installation/Additional_Information_and_Known_Issues.html#gpfs-file-system):

-----

GPFS file system<https://www.scm.com/doc/Installation/Additional_Information_and_Known_Issues.html#gpfs-file-system>

Starting with AMS2019, the KF sub-system (used for handling binary files such as ADF?s TAPE* files) has been rewritten to use memory-mapped files. The mmap() system call implementation is file-system dependent and, unfortunately, it is not equally efficient in different file systems. The memory-mapped files implementation in GPFS is extremely inefficient. Therefore the users should avoid using a GPFS for scratch files

--------

Is this claim true? Are there caveats to this statement, if true?

Thanks,

Oluwasijibomi (Siji) Saula

HPC Systems Administrator  /  Information Technology

Research 2 Building 220B / Fargo ND 58108-6050

p: 701.231.7749 / www.ndsu.edu<http://www.ndsu.edu/>

[cid:image001.gif at 01D57DE0.91C300C0]

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Message: 2
Date: Tue, 22 Jun 2021 15:55:54 +0000
From: Simon Thompson <S.J.Thompson at bham.ac.uk>
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] GPFS bad at memory-mapped files?
Message-ID: <14CCBDE7-AB03-456B-806B-6AD1A8270A7D at bham.ac.uk>
Content-Type: text/plain; charset="utf-8"

There certainly *were* issues.

See for example: http://files.gpfsug.org/presentations/2018/London/6_GPFSUG_EBI.pdf
And the follow on IBM talk on the same day: http://files.gpfsug.org/presentations/2018/London/6_MMAP_V2.pdf

And also from this year: https://www.spectrumscaleug.org/event/ssugdigital-spectrum-scale-expert-talks-update-on-performance-enhancements-in-spectrum-scale/

So it may have been true. If it still is, maybe, but it will depend on your GPFS code.

Simon

From: <gpfsug-discuss-bounces at spectrumscale.org> on behalf of "Saula, Oluwasijibomi" <oluwasijibomi.saula at ndsu.edu>
Reply to: "gpfsug-discuss at spectrumscale.org" <gpfsug-discuss at spectrumscale.org>
Date: Tuesday, 22 June 2021 at 16:17
To: "gpfsug-discuss at spectrumscale.org" <gpfsug-discuss at spectrumscale.org>
Subject: [gpfsug-discuss] GPFS bad at memory-mapped files?

Hello,

While reviewing AMS software suite for installation, I noticed this remark (https://www.scm.com/doc/Installation/Additional_Information_and_Known_Issues.html#gpfs-file-system):

-----

GPFS file system

Starting with AMS2019, the KF sub-system (used for handling binary files such as ADF?s TAPE* files) has been rewritten to use memory-mapped files. The mmap() system call implementation is file-system dependent and, unfortunately, it is not equally efficient in different file systems. The memory-mapped files implementation in GPFS is extremely inefficient. Therefore the users should avoid using a GPFS for scratch files
--------

Is this claim true? Are there caveats to this statement, if true?

Thanks,

Oluwasijibomi (Siji) Saula

HPC Systems Administrator  /  Information Technology

Research 2 Building 220B / Fargo ND 58108-6050

p: 701.231.7749 / www.ndsu.edu<http://www.ndsu.edu/>

[cid:image001.gif at 01D57DE0.91C300C0]

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