On 7/30/19 2:55 PM, Dennis Zhou wrote:
On Tue, Jul 30, 2019 at 02:13:25PM -0700, sathyanarayanan kuppuswamy wrote:
On 7/30/19 1:54 PM, Dave Hansen wrote:
On 7/30/19 1:46 PM, Uladzislau Rezki wrote:
+ /*
+ * If required width exeeds current VA block, move
+ * base downwards and then recheck.
+ */
+ if (base + end > va->va_end) {
+ base = pvm_determine_end_from_reverse(&va, align) - end;
+ term_area = area;
+ continue;
+ }
+
/*
* If this VA does not fit, move base downwards and recheck.
*/
- if (base + start < va->va_start || base + end > va->va_end) {
+ if (base + start < va->va_start) {
va = node_to_va(rb_prev(&va->rb_node));
base = pvm_determine_end_from_reverse(&va, align) - end;
term_area = area;
--
2.21.0
I guess it is NUMA related issue, i mean when we have several
areas/sizes/offsets. Is that correct?
I don't think NUMA has anything to do with it. The vmalloc() area
itself doesn't have any NUMA properties I can think of. We don't, for
instance, partition it into per-node areas that I know of.
I did encounter this issue on a system with ~100 logical CPUs, which is
a moderate amount these days.
I agree with Dave. I don't think this issue is related to NUMA. The problem
here is about the logic we use to find appropriate vm_area that satisfies
the offset and size requirements of pcpu memory allocator.
In my test case, I can reproduce this issue if we make request with offset
(ffff000000) and size (600000).
--
Sathyanarayanan Kuppuswamy
Linux kernel developer
I misspoke earlier. I don't think it's numa related either, but I think
you could trigger this much more easily this way as it could skip more
viable vma space because it'd have to find more holes.
But it seems that pvm_determine_end_from_reverse() will return the free
vma below the address if it is aligned so:
base + end > va->va_end
will always be true and then push down the searching va instead of using
that va first.
It won't be always true. Initially base address is calculated as below:
base = pvm_determine_end_from_reverse(&va, align) - end;
So for first iteration it will not fail.
Thanks,
Dennis
--
Sathyanarayanan Kuppuswamy
Linux kernel developer
