On 2/3/25 20:07, Paul E. McKenney wrote: > On Mon, Feb 03, 2025 at 10:28:46AM +0100, Vlastimil Babka wrote: >> Following the move of the TREE_RCU batching kvfree_rcu() implementation >> to slab, we still have the simple non-batching implementation in tiny >> RCU, and RCU implementation specific ifdefs in slab code. >> >> Finish the move and integration into slab. Allow using the simple >> call_rcu() based implementation also with tree RCU when SLUB_TINY is >> enabled, as its goal is also to limit memory footprint with less concern >> for top performance. >> >> In order to avoid RCU having to recognize the fake callback function >> pointers (__is_kvfree_rcu_offset()) when handling call_rcu(), implement >> a callback that can calculate the object's address from the embedded >> rcu_head pointer without knowing the specific offset (previously SLOB >> would not have made it possible, but it's gone now). >> >> After this series, AFAIK only the following kvfree_rcu specific code >> remains in RCU: >> >> - a call to kfree_rcu_scheduler_running() from rcu_set_runtime_mode() >> >> - probably necessary and a generic registration interface would be >> unnecessary bloat? > > I am OK with this calling directly. > > Alternatively, you could create a core_initcall() that did nothing > but invoke kfree_rcu_scheduler_running(), and then drop that call from > rcu_set_runtime_mode(). Up to you guys! I was afraid there's some ordering necessary with the rest of what rcu_set_runtime_mode() does, but perhaps there's actually not. >> - declarations of kfree_rcu() API in include/linux/rcupdate.h >> >> - could be moved to slab.h after checking for/fixing up potential >> missing includes > > It would be good to move them, but no real hurry from this end. > >> git tree: >> https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=b4/slub-tiny-kfree_rcu >> >> Changes since RFC [1]: >> - Rebased to v6.14-rc1 >> - Fixed build errors reported by bots. >> - Changed where kvfree_call_rcu() is moved to in patch 1 to avoid another >> move in patch 4. >> - R-b's by Ulad and Joel >> - Fix a memory leak in kvfree_rcu_list() thanks to Ulad >> - Various comments' improvements and fixes (Joel, Ulad) >> - Rename config to CONFIG_KFREE_RCU_BATCHED (Ulad) >> >> Due to changes, didn't keep Paul's Tested-by (but thanks!) > > I re-ran the tests, so feel free to add it back in. ;-) Thanks, will do :)
