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https://issues.apache.org/jira/browse/MESOS-6765?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benjamin Mahler updated MESOS-6765:
-----------------------------------
Labels: performance (was: )
> Consider making the Resources wrapper "copy-on-write" to improve performance.
> -----------------------------------------------------------------------------
>
> Key: MESOS-6765
> URL: https://issues.apache.org/jira/browse/MESOS-6765
> Project: Mesos
> Issue Type: Improvement
> Reporter: Benjamin Mahler
> Labels: performance
>
> Resources currently directly stores the underlying resource objects:
> {code}
> class Resources
> {
> ...
> std::vector<Resource_> resources;
> };
> {code}
> What this means is that copying of Resources (which occurs frequently) is
> expensive since copying a {{Resource}} object is relatively heavy-weight.
> One strategy, in MESOS-4770, is to avoid protobuf in favor of C++ types (i.e.
> replace {{Value::Scalar}}, {{Value::Set}}, and {{Value::Ranges}} with C++
> equivalents). However, metadata like reservations, disk info, etc, is still
> fairly expensive to copy even if avoiding protobufs.
> An approach to reduce copying would be to only copy the resource objects upon
> writing, when there are multiple references to the resource object. If there
> is a single reference to the resource object we could safely mutate it
> without copying. E.g.
> {code}
> class Resource
> {
> ...
> std::vector<shared_ptr<Resource_>> resources;
> };
> // Mutation function:
> void Resources::mutate(size_t index)
> {
> // Copy if there are multiple references.
> if (resources[i].use_count() > 1) {
> resources[i] = copy(resources[i]);
> }
> // Mutate safely.
> resources[i].some_mutation();
> }
> {code}
> On the other hand, this introduces a additional level of pointer chasing. So
> we would need to weigh the approaches.
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