Messages in this thread | | | Date | Tue, 31 Mar 2009 18:25:25 +0200 | From | Andrea Arcangeli <> | Subject | Re: [PATCH 4/4] add ksm kernel shared memory driver. |
| |
On Tue, Mar 31, 2009 at 10:54:57AM -0500, Anthony Liguori wrote: > You can still disable ksm and simply return ENOSYS for the MADV_ flag. You
-EINVAL if something, -ENOSYS would tell userland that it shall stop trying to use madvise, including the other MADV_ too.
> could even keep it as a module if you liked by separating the madvise bits > from the ksm bits. The madvise() bits could just provide the tracking > infrastructure for determine which vmas were currently marked as sharable. > You could then have ksm as loadable module that consumed that interface to > then perform scanning.
What's the point of making ksm a module if one has part of ksm code loaded in the kernel and not being possible to avoid compiling in? People that says KSM=N in their .config (like embedded running with 1M of ram), don't want that tracking overhead compiled into the kernel.
Returning -EINVAL would be an option but again I think madvise is core syscall for SuS and I don't like that those core VM parts returns -EINVAL at will depend on certain kernel modules being loaded.
> A number of MADV_ flags are Linux specific (like > MADV_DOFORK/MADV_DONTFORK).
But those aren't kernel module related, so they're in line with the standard ones and could be adapted by other OS.
KSM is not a core VM functionality, madvise is a core VM functionality, so I don't see fit. KSM as ioctl or KSM creating /proc/<pid>/ksm when loaded, sounds fine to me instead. If open of either one fails, application won't register in. It's up to you to choose KSM=M/N, if you want it as core functionality just build as KSM=Y but leave the option to others to save memory.
| |