On 2023/2/16 15:51, Michal Hocko wrote:
On Thu 16-02-23 07:11:19, Qi Zheng wrote:
On 2023/2/16 00:36, Michal Hocko wrote:
On Wed 15-02-23 23:24:10, Qi Zheng wrote:
Hi all,
Currently, in the process of initialization or offline memory, memoryless
nodes will still be built into the fallback list of itself or other nodes.
This is not what we expected, so this patch series removes memoryless
nodes from the fallback list entirely.
Comments and suggestions are welcome.
Hi Michal,
This is a tricky area full of surprises and it is really easy to
Would you mind giving an example of a "new problem"?
The initialization is spread over several places and it is quite easy to
introduce bugs because it is hard to review this area. Been there done
that. Just look into the git log.
I understand your concern, but should we therefore reject all revisions
to this?
introduce new problems. What kind of problem/issue are you trying to
solve/handle by these changes?
IIUC, I think there are two reasons:
Firstly, as mentioned in commit message, the memoryless node has no
memory to allocate (If it can be allocated, it may also cause the panic
I mentioned in [1]), so we should not continue to traverse it when
allocating memory at runtime, which will have a certain overhead.
Sure that is not the most optimal implementation but does this matter in
practice? Can you observe any actual measurable performance penalty?
No, and the original reason for noticing this place was the panic I
mentioned in [1] (< NODE_MIN_SIZE). And if we had handled the memoryless
node's zonelist correctly before, we wouldn't have had that panic at
all.
Currently we are just sacrificing some tiny performance for a
simplicity.
Hmm, I don't think my modification complicates the code.
Secondly, from the perspective of semantic correctness, why do we remove
the memoryless node from the fallback list of other normal nodes
(N_MEMORY), but not from its own fallback list (PATCH[1/2])? Why should
an upcoming memoryless node continue exist in the fallback list of
itself and other normal nodes (PATCH[2/2])?
I am not sure I follow. What is the semantic correctness issue?
Sorry for the ambiguity, what I meant was that memoryless nodes should
never have been built into any fallback list, not just for performance
optimizations.
--
Thanks,
Qi
