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Forum Topic - [QNX7] x86_64 missing support for "big pages" (2MB): (3 Items)

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Davide Ancri

10/19/2017 3:24 AM

post118128

[QNX7] x86_64 missing support for "big pages" (2MB)

hi all

a simple call to getpagesizes() shows that qnx7 x86_64 kernel supports only 4 KB pages, while qnx6.5 x86 supports both 
4KB and 2MB "big pages" with no need for special configuration/options into the mkifs buildfile.

Is there a reason for not supporting big pages in x86_64 qnx7? Is is possible to enable big pages via startup/procnto 
configuration?

We tuned many memory allocations in order to exploit the bigpages performaces increase under qnx6, and we would like to 
keep these optimizaions under qnx7 also.

thanks in advance!
Davide

Elad Lahav

10/19/2017 10:00 PM

post118130

Re: [QNX7] x86_64 missing support for "big pages" (2MB)

See my response on the other question. It is extremely difficult to provide on-demand paging in the presence of multiple
 page sizes. It also makes the physical allocator much slower for the single-page case.

--Elad

Davide Ancri

10/20/2017 9:52 AM

post118135

Re: [QNX7] x86_64 missing support for "big pages" (2MB)

Exploiting the big pages performaces has been important for some specific tasks, in our design.

We will measure performaces once completed the full porting to qnx7, hoping the 64-bits improvements will compensate for
 the missing bigpage support.

thanks!
Davide

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