Hi,
On 10/19/2017 12:18 AM, Tomasz Nowicki wrote:
On 18.10.2017 19:30, Jeremy Linton wrote:
On 10/18/2017 05:24 AM, Tomasz Nowicki wrote:
On 18.10.2017 07:39, Tomasz Nowicki wrote:
On 17.10.2017 17:22, Jeremy Linton wrote:
On 10/17/2017 08:25 AM, Tomasz Nowicki wrote:
On 12.10.2017 21:48, Jeremy Linton wrote:
(trimming)
+ if (*found != NULL)
+ pr_err("Found duplicate cache level/type unable
to determine uniqueness\n");
Actually I still see this error messages in my dmesg. It is because
the following ThunderX2 per-core L1 and L2 cache hierarchy:
Core
------------------
| |
| L1i ----- |
| | |
| ----L2 |
| | |
| L1d ----- |
| |
------------------
In this case we have two paths which lead to L2 cache and hit above
case. Is it really error case?
No, but its not deterministic unless we mark the node, which doesn't
solve the problem of a table constructed like
L1i->L2 (unified)
L1d->L2 (unified)
or various other structures which aren't disallowed by the spec and
have non-deterministic real world meanings, anymore than constructing
the table like:
L1i
Lid->L2(unified)
which I tend to prefer because with a structuring like that it can be
deterministic (and in a way actually represents the non-coherent
behavior of (most?) ARM64 core's i-caches, as could be argued the
first example if the allocation policies are varied between the L2
nodes).
The really ugly bits here happen if you add another layer:
L1i->L2i-L3
L1d------^
which is why I made that an error message, not including the fact that
since the levels aren't tagged the numbering and meaning isn't clear.
(the L1i in the above example might be better called an L0i to avoid
throwing off the reset of the hierarchy numbering, also so it could be
ignored).
Summary:
I'm not at all happy with this specification's attempt to leave out
pieces of information which make parsing things more deterministic. In
this case I'm happy to demote the message level, but not remove it
entirely but I do think the obvious case you list shouldn't be the
default one.
Lastly:
I'm assuming the final result is that the table is actually being
parsed correctly despite the ugly message?
Indeed, the ThunderX2 PPTT table is being parsed so that topology shown
in lstopo and lscpu is correct.
Great.
Also, I think this is a better change:
if ((*found != NULL) && (*found != cache))
pr_err("Found duplicate cache level/type unable to determine
uniqueness\n");
Which if its a duplicate node/type at the given level the message is
just suppressed. It will of course still trigger in cases like:
L1d->L2
l1i->L2
or other odd cases.
