On Wed, 7 Aug 2019, Jon Derrick wrote: Cc+: Ming, Christoph.
Left context for reference. > The current irq spreading algorithm spreads vectors amongst cpus evenly > per node. If a node has more cpus than another node, the extra vectors > being spread may not be reported back to the caller. > > This is most apparent with the NVMe driver and nr_cpus < vectors, where > the underreporting results in the caller's WARN being triggered: > > irq_build_affinity_masks() > ... > if (nr_present < numvecs) > WARN_ON(nr_present + nr_others < numvecs); > > Signed-off-by: Jon Derrick <[email protected]> > --- > kernel/irq/affinity.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c > index 4352b08ae48d..9beafb8c7e92 100644 > --- a/kernel/irq/affinity.c > +++ b/kernel/irq/affinity.c > @@ -127,7 +127,8 @@ static int __irq_build_affinity_masks(unsigned int > startvec, > } > > for_each_node_mask(n, nodemsk) { > - unsigned int ncpus, v, vecs_to_assign, vecs_per_node; > + unsigned int ncpus, v, vecs_to_assign, total_vecs_to_assign, > + vecs_per_node; > > /* Spread the vectors per node */ > vecs_per_node = (numvecs - (curvec - firstvec)) / nodes; > @@ -141,14 +142,16 @@ static int __irq_build_affinity_masks(unsigned int > startvec, > > /* Account for rounding errors */ > extra_vecs = ncpus - vecs_to_assign * (ncpus / vecs_to_assign); > + total_vecs_to_assign = vecs_to_assign + extra_vecs; > > - for (v = 0; curvec < last_affv && v < vecs_to_assign; > + for (v = 0; curvec < last_affv && v < total_vecs_to_assign; > curvec++, v++) { > cpus_per_vec = ncpus / vecs_to_assign; > > /* Account for extra vectors to compensate rounding > errors */ > if (extra_vecs) { > cpus_per_vec++; > + v++; > --extra_vecs; > } > irq_spread_init_one(&masks[curvec].mask, nmsk, > -- > 2.20.1 > >
