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Commit b4816919 authored by Matthew Pickering's avatar Matthew Pickering Committed by Marge Bot
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testsuite: Pass -kb16k -kc128k for performance tests

Setting a larger stack chunk size gives a greater protection
from stack thrashing (where the repeated overflow/underflow allocates a lot of
stack chunks which sigificantly impact allocations). This
stabilises some tests against differences cause by more things being
pushed onto the stack.

The performance tests are generally testing work done by the compiler,
using allocation as a proxy, so removing/stabilising the allocations due
to the stack gives us more stable tests which are also more sensitive
to actual changes in compiler performance.

The tests which increase are ones where we compile a lot of modules, and
for each module we spawn a thread to compile the module in. Therefore
increasing these numbers has a multiplying effect on these tests because
there are many more stacks which we can increase in size.

The most significant improvements though are cases such as T8095 which
reduce significantly in allocations (30%). This isn't a performance
improvement really but just helps stabilise the test against this
threshold set by the defaults.

Fixes #23439

-------------------------
Metric Decrease:
    InstanceMatching
    T14683
    T8095
    T9872b_defer
    T9872d
    T9961
    hie002
    T19695
    T3064
Metric Increase:
    MultiLayerModules
    T13701
    T14697
-------------------------
parent 0350b186
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