On Thu, Jan 23, 2025 at 11:37:17AM +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? > > - declarations of kfree_rcu() API in include/linux/rcupdate.h > > - could be moved to slab.h after checking for/fixing up potential > missing includes > > git tree: > https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/linux.git/log/?h=b4/slub-tiny-kfree_rcu Looks good to me, except typo in third patch 'kmalloc of vmalloc allocation' should be 'kmalloc or vmalloc allocation'. Maybe also add some comments on top of 'kvfree_rcu_cb()'. Like: /* * Given an rcu_head embedded within an object at an offset < 4k, * free the object in question. */ I like the touch with the config option in the last patch! Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> thanks, - Joel > To: Christoph Lameter <cl@xxxxxxxxx> > To: David Rientjes <rientjes@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx> > Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx> > Cc: linux-mm@xxxxxxxxx > To: "Paul E. McKenney" <paulmck@xxxxxxxxxx> > To: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> > To: Josh Triplett <josh@xxxxxxxxxxxxxxxx> > To: Boqun Feng <boqun.feng@xxxxxxxxx> > To: Uladzislau Rezki <urezki@xxxxxxxxx> > Cc: Steven Rostedt <rostedt@xxxxxxxxxxx> > Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> > Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> > Cc: Zqiang <qiang.zhang1211@xxxxxxxxx> > Cc: rcu@xxxxxxxxxxxxxxx > > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> > --- > Vlastimil Babka (4): > slab, rcu: move TINY_RCU variant of kvfree_rcu() to SLAB > rcu: remove trace_rcu_kvfree_callback > rcu, slab: use a regular callback function for kvfree_rcu > slab: don't batch kvfree_rcu() with SLUB_TINY > > include/linux/rcupdate.h | 29 ++++++++++++++--------------- > include/linux/rcutiny.h | 36 ------------------------------------ > include/linux/rcutree.h | 3 --- > include/linux/slab.h | 14 ++++++++++++++ > include/trace/events/rcu.h | 34 ---------------------------------- > kernel/rcu/tiny.c | 24 ------------------------ > kernel/rcu/tree.c | 9 ++------- > mm/Kconfig | 4 ++++ > mm/slab.h | 2 ++ > mm/slab_common.c | 32 +++++++++++++++++++++++++------- > mm/slub.c | 42 ++++++++++++++++++++++++++++++++++++++++++ > 11 files changed, 103 insertions(+), 126 deletions(-) > --- > base-commit: e492fac3657b60b8dd78a6e8ca26d1d14706c7b3 > change-id: 20250123-slub-tiny-kfree_rcu-bd65bfe222f2 > > Best regards, > -- > Vlastimil Babka <vbabka@xxxxxxx> >
