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Discuss GC pauses

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Antoine Pitrou 2017-09-08 17:47:33 +02:00
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@ -350,8 +350,8 @@ in deterministic visible behaviour anyway. Second because the GC deals
with reference cycles while many objects are reclaimed immediately when their with reference cycles while many objects are reclaimed immediately when their
last visible reference disappears. last visible reference disappears.
Impact on performance Impact on CPU consumption
--------------------- -------------------------
The pseudo-code above adds two lock operations for each implicit collection The pseudo-code above adds two lock operations for each implicit collection
request in "threaded" mode: one in the thread making the request (a request in "threaded" mode: one in the thread making the request (a
@ -368,6 +368,19 @@ speculation and superscalar execution).
Actual measurements on worst-case mini-benchmarks may help provide Actual measurements on worst-case mini-benchmarks may help provide
reassuring upper bounds. reassuring upper bounds.
Impact on GC pauses
-------------------
While this PEP does not concern itself with GC pauses, there is a
practical chance that releasing the GIL at some point during an implicit
collection (for example by virtue of executing a pure Python finalizer)
will allow application code to run in-between, lowering the *visible* GC
pause time for some applications.
If this PEP is accepted, future work may try to better realize this potential
by speculatively releasing the GIL during collections, though it is unclear
how doable that is.
Open issues Open issues
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