On 2023/10/31 03:25, Christoph Lameter wrote: > On Sat, 28 Oct 2023, Chengming Zhou wrote: > >> 2. But for full slab (slab->freelist == NULL), PG_workingset is not much useful, we don't >> safely know whether it's used as the cpu slab or not just from this flag. So __slab_free() >> still rely on the "frozen" bit to know it. >> >> 3. And the maintaining of "frozen" has no extra cost now, since it's changed together with "freelist" >> and other counter using cmpxchg, we already have the cmpxchg when start to use a slab as the cpu slab. >> >> Maybe I missed something, I don't know how to drop the frozen flag. > > > Maybe frozen is now = PG_Workingset | cmpxchg-frozen? > > The current scheme (which this series implemented) is: - node partial slabs: PG_Workingset (set or clear with per-node list_lock protection) - cpu partial slabs: !PG_Workingset - cpu slabs: !PG_Workingset && frozen (set or clear using cmpxchg together with freelist) - full slabs: !PG_Workingset As Vlastimil noted, it's possible to drop "frozen" bit for cpu slabs, but we keep it for performance, since we don't need to grab node list_lock to check whether PG_Workingset is set or not if the "frozen" bit is set. Thanks!
