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EOfmlgGuYq/Ad95y3G/tDYDJS1OUP/nZxqkIZjwnv3ND9GBIZs2RXeMHyJF37DFVVDTjT14eRp6 IlN2qMXyP/+CvPW9J+b4/+ouTVP8WQ3xOY6bDQjpy6htshs8pMwMgxgOQu058Sa5dgMbZJ4UANz HHz6S1/VGq4vWd+juoP9s3PGjq/nsQ3tpv/Bp4YwAIZV0XeB7ZYQUDGvR2vd6jqUOXiEpu3ciMP fpK5PhCsWedg//JoMlrGKi6IPzF4Mg== X-Proofpoint-GUID: 0jpP4Nx5otxFclIqHm5LtB8DnyLFEAeS X-Authority-Analysis: v=2.4 cv=IZWHWXqa c=1 sm=1 tr=0 ts=68abf30e b=1 cx=c_pps a=e1sVV491RgrpLwSTMOnk8w==:117 a=e1sVV491RgrpLwSTMOnk8w==:17 a=6eWqkTHjU83fiwn7nKZWdM+Sl24=:19 a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=2OwXVqhp2XgA:10 a=GoEa3M9JfhUA:10 a=VwQbUJbxAAAA:8 a=PuvxfXWCAAAA:8 a=yPCof4ZbAAAA:8 a=54Tjv0WagPEaDX3YVhoA:9 a=CjuIK1q_8ugA:10 a=uAr15Ul7AJ1q7o2wzYQp:22 cc=ntf awl=host:13600 X-Proofpoint-ORIG-GUID: 0jpP4Nx5otxFclIqHm5LtB8DnyLFEAeS On Wed, Jul 23, 2025 at 03:34:42PM +0200, Vlastimil Babka wrote: > Since we don't control the NUMA locality of objects in percpu sheaves, > allocations with node restrictions bypass them. Allocations without > restrictions may however still expect to get local objects with high > probability, and the introduction of sheaves can decrease it due to > freed object from a remote node ending up in percpu sheaves. > > The fraction of such remote frees seems low (5% on an 8-node machine) > but it can be expected that some cache or workload specific corner cases > exist. We can either conclude that this is not a problem due to the low > fraction, or we can make remote frees bypass percpu sheaves and go > directly to their slabs. This will make the remote frees more expensive, > but if if's only a small fraction, most frees will still benefit from > the lower overhead of percpu sheaves. > > This patch thus makes remote object freeing bypass percpu sheaves, > including bulk freeing, and kfree_rcu() via the rcu_free sheaf. However > it's not intended to be 100% guarantee that percpu sheaves will only > contain local objects. The refill from slabs does not provide that > guarantee in the first place, and there might be cpu migrations > happening when we need to unlock the local_lock. Avoiding all that could > be possible but complicated so we can leave it for later investigation > whether it would be worth it. It can be expected that the more selective > freeing will itself prevent accumulation of remote objects in percpu > sheaves so any such violations would have only short-term effects. > > Signed-off-by: Vlastimil Babka > --- > mm/slab_common.c | 7 +++++-- > mm/slub.c | 42 ++++++++++++++++++++++++++++++++++++------ > 2 files changed, 41 insertions(+), 8 deletions(-) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 2d806e02568532a1000fd3912db6978e945dcfa8..f466f68a5bd82030a987baf849a98154cd48ef23 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1623,8 +1623,11 @@ static bool kfree_rcu_sheaf(void *obj) > > slab = folio_slab(folio); > s = slab->slab_cache; > - if (s->cpu_sheaves) > - return __kfree_rcu_sheaf(s, obj); > + if (s->cpu_sheaves) { > + if (likely(!IS_ENABLED(CONFIG_NUMA) || > + slab_nid(slab) == numa_node_id())) > + return __kfree_rcu_sheaf(s, obj); > + } This should be numa_mem_id() to handle memory-less NUMA nodes as Christoph mentioned [1]? I saw you addressed this in most of places but not this one. With that addressed, please feel free to add: Reviewed-by: Harry Yoo [1] https://lore.kernel.org/linux-mm/c60ae681-6027-0626-8d4e-5833982bf1f0@gentwo.org > > return false; > } -- Cheers, Harry / Hyeonggon