Re: Accessing user memory and minor page faults


Gianluca Borello <g.borello@...>
 

On Fri, Oct 6, 2017 at 3:11 AM, Alexei Starovoitov
<alexei.starovoitov@...> wrote:

not following why all fs-es need to be patched.
can we do a mini version of filemap_fault() that only operates
on pages in cache? We cannot serve major faults anyway and real
fs access is not necessary.
Good point. Indeed we can, I thought a strategy might have been
leaving the helper implementation as generic as possible and rely on a
call to vma->vm_ops->access() if present, but it seems we could
definitely try to directly look into the page cache if we see
vma->vm_file->f_mapping exists, bypassing the vm_ops (hope that's what
you meant).

btw the .config-s I care about don't have CONFIG_NUMA_BALANCING set.
It's interesting, most kernels I've seen don't have the feature
enabled by default, whereas all Ubuntu kernels, widely used on
servers, have it.


yep. same here. It's not urgent, but we need a solution long term.
Thanks! I'll be glad to experiment with some of this at some point :)

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