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Re: [Xen-devel] [PATCH] don't use mlock() with Solaris tools

On Oct 22, 2006, at 2:16 PM, Keir Fraser wrote:

On 22/10/06 7:02 pm, "John Levon" <levon@xxxxxxxxxxxxxxxxx> wrote:

# HG changeset patch
# User john.levon@xxxxxxx
# Date 1161315500 25200
# Node ID ad404ee927926b8cc4a6498b180e78f0939eb2eb
# Parent  3685871c6f7930c7d35baea7cee4f51d00415796
on solaris: mlock requires a page aligned address and mlock doesn't ensure
the pages won't minor page fault; so don't use it on solaris.

This isn't in unstable yet; I don't know if it was missed or if there's
some better way we could do this?


Don't worry, it's in my to-apply list. I don't do FIFO. :-)

Hey, hang on a minute.
If you are gonna add this then can we abstract this to the arches and with somethign better than an ifdef?
The locking makes no sense in PPC (even on linux) either.

Hollis and I touched on this and has been the bane of our existence since we were required to have Xen interpret user level pointers, thread started here: http://lists.xensource.com/archives/html/xen-devel/2005-08/ msg00719.html

I cannot speak for Hollis (I think he may actually disagree with me) but see this as an opportunity to design something better, or at least have the debat (again). What might be a better alternative an to actually have an allocate call rather than an mlock call where the arches and OSes could to what is best for them.
So what is done on x86 could be:
  do { x = alloca(len); mlock (x, len); } while (0)

but where solaris and other arches could do something more.

BTW: John, how do you solve the minor faults?!


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