On Wed, May 24, 2023 at 11:32:47AM +0200, Peter Zijlstra wrote:
On Mon, May 15, 2023 at 09:57:07AM +0200, Peter Zijlstra wrote:
quoted
@@ -3008,6 +3029,22 @@ static inline bool pfmemalloc_match(stru
}
#ifndef CONFIG_SLUB_TINY
+static inline bool
+__update_cpu_freelist_fast(struct kmem_cache *s,
+ void *freelist_old, void *freelist_new,
+ unsigned long tid)
+{
+#ifdef system_has_freelist_aba
+ freelist_aba_t old = { .freelist = freelist_old, .counter = tid };
+ freelist_aba_t new = { .freelist = freelist_new, .counter = next_tid(tid) };
+
+ return this_cpu_cmpxchg_freelist(s->cpu_slab->freelist_tid.full,
+ old.full, new.full) == old.full;
+#else
+ return false;
+#endif
+}
+
/*
* Check the slab->freelist and either transfer the freelist to the
* per cpu freelist or deactivate the slab.@@ -3359,11 +3396,7 @@ static __always_inline void *__slab_allo
* against code executing on this cpu *not* from access by
* other cpus.
*/
- if (unlikely(!this_cpu_cmpxchg_double(
- s->cpu_slab->freelist, s->cpu_slab->tid,
- object, tid,
- next_object, next_tid(tid)))) {
-
+ if (unlikely(!__update_cpu_freelist_fast(s, object, next_object, tid))) {
note_cmpxchg_failure("slab_alloc", s, tid);
goto redo;
}@@ -3736,11 +3769,7 @@ static __always_inline void do_slab_free
set_freepointer(s, tail_obj, freelist);
- if (unlikely(!this_cpu_cmpxchg_double(
- s->cpu_slab->freelist, s->cpu_slab->tid,
- freelist, tid,
- head, next_tid(tid)))) {
-
+ if (unlikely(!__update_cpu_freelist_fast(s, freelist, head, tid))) {
note_cmpxchg_failure("slab_free", s, tid);
goto redo;
}
This isn't right; the this_cpu_cmpxchg_double() was unconditional and
relied on the local_irq_save() fallback when no native cmpxchg128 is
present.
This then also means I need to look at this_cpu_cmpxchg128 and
this_cpu_cmoxchg64 behaviour when we dont have the CPUID feature.
Because current verions seem to assume the instruction is present.