Harry wrote: > [Resending after fixing broken email headers] > > On Fri, Apr 10, 2026 at 02:19:37PM +0200, Thomas Gleixner wrote: > > The decision whether to scan remote nodes is based on a 'random' number > > retrieved via get_cycles(). get_cycles() is about to be removed. > > > > There is already prandom state in the code, so use that instead. > > > > Signed-off-by: Thomas Gleixner <[email protected]> > > Cc: Vlastimil Babka <[email protected]> > > Cc: [email protected] > > --- > > Acked-by: Harry Yoo (Oracle) <[email protected]> > > Is this for this merge window? > > This may conflict with upcoming changes on freelist shuffling [1] > (not queued for slab/for-next yet though), but it should be easy to > resolve. >
Hi Harry, Would you like me to wait for this patch to land linux-next and then rebase and send v6 on top? Thanks, -- With Best Regards, Shengming > [Cc'ing Shengming and SLAB ALLOCATOR folks] > [1] > https://lore.kernel.org/linux-mm/[email protected] > > -- > Cheers, > Harry / Hyeonggon > > > mm/slub.c | 37 +++++++++++++++++++++++-------------- > > 1 file changed, 23 insertions(+), 14 deletions(-) > > > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -3302,6 +3302,25 @@ static inline struct slab *alloc_slab_pa > > return slab; > > } > > > > +#if defined(CONFIG_SLAB_FREELIST_RANDOM) || defined(CONFIG_NUMA) > > +static DEFINE_PER_CPU(struct rnd_state, slab_rnd_state); > > + > > +static unsigned int slab_get_prandom_state(unsigned int limit) > > +{ > > + struct rnd_state *state; > > + unsigned int res; > > + > > + /* > > + * An interrupt or NMI handler might interrupt and change > > + * the state in the middle, but that's safe. > > + */ > > + state = &get_cpu_var(slab_rnd_state); > > + res = prandom_u32_state(state) % limit; > > + put_cpu_var(slab_rnd_state); > > + return res; > > +} > > +#endif > > + > > #ifdef CONFIG_SLAB_FREELIST_RANDOM > > /* Pre-initialize the random sequence cache */ > > static int init_cache_random_seq(struct kmem_cache *s) > > @@ -3365,8 +3384,6 @@ static void *next_freelist_entry(struct > > return (char *)start + idx; > > } > > > > -static DEFINE_PER_CPU(struct rnd_state, slab_rnd_state); > > - > > /* Shuffle the single linked freelist based on a random pre-computed > > sequence */ > > static bool shuffle_freelist(struct kmem_cache *s, struct slab *slab, > > bool allow_spin) > > @@ -3383,15 +3400,7 @@ static bool shuffle_freelist(struct kmem > > if (allow_spin) { > > pos = get_random_u32_below(freelist_count); > > } else { > > - struct rnd_state *state; > > - > > - /* > > - * An interrupt or NMI handler might interrupt and change > > - * the state in the middle, but that's safe. > > - */ > > - state = &get_cpu_var(slab_rnd_state); > > - pos = prandom_u32_state(state) % freelist_count; > > - put_cpu_var(slab_rnd_state); > > + pos = slab_get_prandom_state(freelist_count); > > } > > > > page_limit = slab->objects * s->size; > > @@ -3882,7 +3891,7 @@ static void *get_from_any_partial(struct > > * with available objects. > > */ > > if (!s->remote_node_defrag_ratio || > > - get_cycles() % 1024 > s->remote_node_defrag_ratio) > > + slab_get_prandom_state(1024) > s->remote_node_defrag_ratio) > > return NULL; > > > > do { > > @@ -7102,7 +7111,7 @@ static unsigned int > > > > /* see get_from_any_partial() for the defrag ratio description */ > > if (!s->remote_node_defrag_ratio || > > - get_cycles() % 1024 > s->remote_node_defrag_ratio) > > + slab_get_prandom_state(1024) > s->remote_node_defrag_ratio) > > return 0; > > > > do { > > @@ -8421,7 +8430,7 @@ void __init kmem_cache_init_late(void) > > flushwq = alloc_workqueue("slub_flushwq", WQ_MEM_RECLAIM | WQ_PERCPU, > > 0); > > WARN_ON(!flushwq); > > -#ifdef CONFIG_SLAB_FREELIST_RANDOM > > +#if defined(CONFIG_SLAB_FREELIST_RANDOM) || defined(CONFIG_NUMA) > > prandom_init_once(&slab_rnd_state); > > #endif > > } > > > >
