ARROW-2558: [Plasma] avoid walk through all the objects when a client disconnects#2015
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zhijunfu wants to merge 3 commits intoapache:masterfrom
Closed
ARROW-2558: [Plasma] avoid walk through all the objects when a client disconnects#2015zhijunfu wants to merge 3 commits intoapache:masterfrom
zhijunfu wants to merge 3 commits intoapache:masterfrom
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pcmoritz
reviewed
May 9, 2018
cpp/src/plasma/plasma.h
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| #endif | ||
| /// Set of clients currently using this object. | ||
| std::unordered_set<Client*> clients; | ||
| /// Reference count. |
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Better documentation is: Number of clients currently using this object.
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Yes this is indeed better:)
pcmoritz
reviewed
May 9, 2018
cpp/src/plasma/plasma.h
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| /// Set of clients currently using this object. | ||
| std::unordered_set<Client*> clients; | ||
| /// Reference count. | ||
| int refcnt; |
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Let's rename this to ref_count, it's good to be not too cryptic ;)
pcmoritz
reviewed
May 9, 2018
cpp/src/plasma/store.cc
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| } | ||
| // Add the client pointer to the list of clients using this object. | ||
| entry->clients.insert(client); | ||
| // Increase refcnt. |
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// Increase reference count.
pcmoritz
reviewed
May 9, 2018
cpp/src/plasma/store.cc
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| auto it = client->object_ids.find(entry->object_id); | ||
| if (it != client->object_ids.end()) { | ||
| client->object_ids.erase(it); | ||
| // Decrease refcnt. |
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// Decrease reference count.
pcmoritz
reviewed
May 9, 2018
cpp/src/plasma/store.cc
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| @@ -533,19 +538,25 @@ void PlasmaStore::disconnect_client(int client_fd) { | |||
| // lists. | |||
| // TODO(swang): Avoid iteration through the object table. | |||
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can remove the TODO(swang) now
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|
Comments addressed. Thanks |
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|
Performance impact: Without this PR: With this PR: So looks like the performance is approximately the same. |
pcmoritz
approved these changes
May 15, 2018
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Currently plasma stores list-of-clients in ObjectTableEntry, which is used to track which clients are using a given object, this serves for two purposes:
A problem with list-of-clients approach is that when a client disconnects, we need to walk through all the objects and remove the client pointer from the list for each object.
Instead, we could add a reference count in ObjectTableEntry, and store list-of-object-ids in client structure. This could both goals that the original approach is targeting, while when a client disconnects, it just walk through its object-ids and dereference each ObjectTableEntry, there's no need to walk through all objects.