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Add a progressive backoff mechanism for barriers.#607

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devinamatthews wants to merge 1 commit intomasterfrom
barrier_backoff
Open

Add a progressive backoff mechanism for barriers.#607
devinamatthews wants to merge 1 commit intomasterfrom
barrier_backoff

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@devinamatthews
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@devinamatthews devinamatthews commented Jan 31, 2022

The mechanism(s) used for backoff must be defined by the configuration or configuration family. Up to three successive mechanisms are supported (e.g. pause/sched_yield/sleep).

Example (in config/<family>/bli_family_<family>.h):

#define BLIS_BARRIER_BACKOFF_1 30    // number of times to loop
#define BLIS_BARRIER_YIELD_1 pause();pause();pause();

//#define BLIS_BARRIER_BACKOFF_2    not needed, the last mechanism is looped forever 
#define BLIS_BARRIER_YIELD_2 sched_yield();

This PR supplants #82 and potentially addresses #604 (family-specific behavior still needs to be decided upon and implemented).

Families needing implementations:

  • Intel
  • AMD (same as Intel?)
  • ARM (v7 same as v8?)
  • POWER
@devinamatthews
Add a progressive backoff mechanism for barriers.
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The mechanism(s) used for backoff must be defined by the configuration or configuration family. Up to three successive mechanisms are supported (e.g. pause/sched_yield/sleep).
@jeffhammond
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jeffhammond commented May 3, 2022

Jim Cownie wrote about this topic here: https://cpufun.substack.com/p/to-sched_yield-or-not-to-sched_yield.
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