RE: [Lhms-devel] [PATCH 0/7] Fragmentation Avoidance V19

[andy@thermo.lanl.gov (Andy Nelson)]

Hi folks,

>Not sure how applications seamlessly can use the proposed hugetlb zone
>based on hugetlbfs.  Depending on the programming language, it might
>actually need changes in libs/tools etc.

This is my biggest worry as well. I can't recall the details
right now, but I have some memories of people telling me, for
example, that large pages on linux were not now available to 
fortran programs period, due to lack of toolchain/lib stuff, 
just as you note. What the reasons were/are I have no idea. I 
do know that the Power 5 numbers I quoted a couple of days ago
required that the sysadmin apply some special patches to linux
and linking to extra library. I don't know what patches (they
came from ibm), but for xlf95 on Power5, the library I had to 
link with was this one:  

    -T /usr/local/lib64/elf64ppc.lbss.x


No changes were required to my code, which is what I need,
but codes that did not link to this library would not run on 
a kernel that had the patches installed, and code that did 
link with this library would not run on a kernel that didn't 
have those patches. 

I don't know what library this is or what was in it, but I 
cant imagine it would have been something very standard or
mainline, with that sort of drastic behavior. Maybe the ibm
folk can explain what this was about.


I will ask some folks here who should know how it may work
on intel/amd machines about how large pages can be used 
this coming week, when I attempt to do page size speed 
testing for my code, as I promised before, as I promised
before, as I promised before. 

Andy


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