<html><head></head><body>Implementation-defined, but it's exactly the same as malloc, which also doesn't promise unfaulted pages. This is one reason some of us keep saying that OpenMP sucks. It's a shitty standard that obstructs better standards from being created.<br><br><div class="gmail_quote">On March 12, 2017 11:19:49 AM MDT, Jeff Hammond <<a href="http://jeff.science">jeff.science</a>@gmail.com> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div><br /><div class="gmail_quote"><div>On Sat, Mar 11, 2017 at 9:00 AM Jed Brown <<a href="mailto:jed@jedbrown.org">jed@jedbrown.org</a>> wrote:<br /></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Jeff Hammond <<a href="mailto:jeff.science@gmail.com" class="gmail_msg" target="_blank">jeff.science@gmail.com</a>> writes:<br class="gmail_msg" />
> I agree 100% that multithreaded codes that fault pages from the main thread in a NUMA environment are doing something wrong ;-)<br class="gmail_msg" />
><br class="gmail_msg" />
> Does calloc *guarantee* pages are not mapped? If I calloc(8), do I get the zero page or part of the arena that's already mapped that is zeroed by the heap manager?<br class="gmail_msg" />
<br class="gmail_msg" />
Is your argument that calloc() should never be used in multi-threaded code?<br class="gmail_msg" />
</blockquote><div><br /></div><div>I never use it for code that I want to behave well in a NUMA environment. </div><div><br /></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br class="gmail_msg" />
If the allocation is larger than MMAP_THRESHOLD (128 KiB by default for<br class="gmail_msg" />
glibc) then it calls mmap. This obviously leaves an intermediate size<br class="gmail_msg" />
that could be poorly mapped (assuming 4 KiB pages), but it's also so<br class="gmail_msg" />
small that it easily fits in cache.</blockquote><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"></blockquote><div><br /></div><div>Is this behavior standardized or merely implementation-defined? I'm not interested in writing code that assumes Linux/glibc. </div><div><br /></div><div>Jeff </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br class="gmail_msg" />
</blockquote></div></div><div dir="ltr">-- <br /></div><div data-smartmail="gmail_signature">Jeff Hammond<br /><a href="mailto:jeff.science@gmail.com" target="_blank">jeff.science@gmail.com</a><br /><a href="http://jeffhammond.github.io/" target="_blank">http://jeffhammond.github.io/</a></div>
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