On 2023/10/31 11:47, Christoph Lameter wrote: > On Tue, 31 Oct 2023, Chengming Zhou wrote: > >> 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 > > And then the frozen flag needs to be set. Otherwise slab_free() would conclude it is on a partial list? > - cpu partial slabs: !PG_Workingset && !frozen Here comes the optimization that "frozen" is not set for the cpu partial slabs, slab_free() will grab node list_lock then check by !PG_Workingset that it's not on a node partial list. >> - cpu slabs: !PG_Workingset && frozen (set or clear using cmpxchg together with freelist) > > > >> - full slabs: !PG_Workingset > > And frozen is clear? Otherwise it is the same as a cpu partial slab. > Right, - full slabs: !PG_Workingset && !frozen Yes, it's the same as a cpu partial slab from only these two flags, but slab_free() also know whether it was full or not. >> 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! >>
