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diff --git a/open_issues/managed_runtime_initiative.mdwn b/open_issues/managed_runtime_initiative.mdwn new file mode 100644 index 00000000..7a880beb --- /dev/null +++ b/open_issues/managed_runtime_initiative.mdwn @@ -0,0 +1,72 @@ +[[!meta copyright="Copyright © 2013 Free Software Foundation, Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!tag open_issue_gnumach]] + + +# IRC, freenode, #hurd, 2013-04-02 + + <psockali> hi again, maybe someone has some metrics + <psockali> is mprotect / munprotect faster in hurd then in linux ? + <pinotree> ? + <psockali> can i protected a memory page against write access in hurd + <psockali> and if so, is it a fast operation ? + <youpi> you can, I never measured, but it's probably the same cost as in + linux + <youpi> I don't see why it would be different, as it boils down to the same + x86 trick + <psockali> but i suppose it is part of the mach kernel doing the protection + and not part of the unix layer ? + <youpi> it is + <youpi> the unix layer doesn't have mm control + <youpi> it has to ask the kernel + <braunr> it's slower on mach, as it's less optimized because of historical + reasons + <braunr> but that's about it + <youpi> less optimized, how so? + <braunr> well, more entry fragmentation + <youpi> in the end you mark the page table and flush the tlb + <braunr> yes + <braunr> the high level virtual memory layer is a bit slower + <youpi> but fragmentation doesn't come into play it you just have one + memory object, does it? + <braunr> it does, as it's about memory areas, not objects + <braunr> the object is merely a backing store + <braunr> protection, inheritance, copy on write are all area (vm_map_entry) + attributes + <braunr> also, some operations affect all the address spaces where a + physical page is mapped + <braunr> although i think linux does the same thing as mach/bsd now + <youpi> but mprotect/munprotect doesn't, does it? + <braunr> no + <braunr> or perhaps by side effect, in some situations, i'm not sure + <braunr> i think it depends if the memory is shared between processes, but + i don't remember the details and can't think of a proper example right + now + <braunr> but anyway, "slower" here is negligible unless address spaces are + really huge and filled with lots of map entries + <braunr> psockali: why do you ask ? + <psockali> can i post a link here ? + <braunr> about what ? + <psockali> it's regarding azul / managed runtime initiative + <psockali> a GC for java + <braunr> why not + <braunr> although i don't see the point for now :) + <psockali> they have a custom MM management module for their GC as linux + kernel modul + <psockali> and i was wondering if mach would be any faster then linux in + that aspect + <psockali> + http://stackoverflow.com/questions/3358545/whats-actually-in-the-managed-runtime-initiatives-kernel-patches-and-jvm + <braunr> psockali: generally speaking, mach is slower than linux because of + its age and the fact it didn't receive as much attention and + microoptimization as linux did + <braunr> psockali: about this article, there is no reason mach would be + faster |