Re: [PATCH v6 20/20] irqdomain: Switch to per-domain locking

[Juergen Gross <jgross@xxxxxxxx>]

On 07.03.23 14:51, David Woodhouse wrote:
> On Mon, 2023-02-13 at 11:43 +0100, Johan Hovold wrote:
> > The IRQ domain structures are currently protected by the global
> > irq_domain_mutex. Switch to using more fine-grained per-domain locking,
> > which can speed up parallel probing by reducing lock contention.
> >
> > On a recent arm64 laptop, the total time spent waiting for the locks
> > during boot drops from 160 to 40 ms on average, while the maximum
> > aggregate wait time drops from 550 to 90 ms over ten runs for example.
> >
> > Note that the domain lock of the root domain (innermost domain) must be
> > used for hierarchical domains. For non-hierarchical domains (as for root
> > domains), the new root pointer is set to the domain itself so that
> > &domain->root->mutex always points to the right lock.
> >
> > Also note that hierarchical domains should be constructed using
> > irq_domain_create_hierarchy() (or irq_domain_add_hierarchy()) to avoid
> > having racing allocations access a not fully initialised domain. As a
> > safeguard, the lockdep assertion in irq_domain_set_mapping() will catch
> > any offenders that also fail to set the root domain pointer.
> >
> > Tested-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx>
> > Tested-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>
> > Signed-off-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
> Broke Xen.
Fixed with commit ad32ab9604f2.


Juergen

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