On 20/11/2021 21:09, Gedare Bloom wrote:
On Mon, Nov 15, 2021 at 10:13 AM Sebastian Huber
<sebastian.hu...@embedded-brains.de> wrote:
If a node is moved from the scheduled chain to the ready queue, then we
know that it is the highest priority ready node. So, it can be
prepended to the ready queue without doing any comparisons.
I'm not certain on the logic here. It is possible for 2 threads X and
Y become ready simultaneously, such that:
X is higher priority than Y. X and Y are higher priority than Z. X
gets scheduled to replace Z, but there is no lower-priority/affine CPU
for Y to get scheduled, so Y will be ready. Then Z is not
higher-priority than Y so it shouldn't be directly prepended.
I think that could happen?
The EDF SMP scheduler supports only one-to-one and one-to-all thread to
processor affinities. The one-to-all threads have a separate ready queue
and there is one ready queue for each processor owned by the scheduler
used for the one-to-one threads. For the ordering across these queues a
64-bit generation number is used. The restriction to one-to-one and
one-to-all affinities is the key property which enables this optimization.
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