Messages in this thread | | | From | Uladzislau Rezki <> | Date | Mon, 16 Mar 2020 19:55:19 +0100 | Subject | Re: [PATCH v1 2/6] rcu: introduce kvfree_rcu() interface |
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On Mon, Mar 16, 2020 at 11:45:39AM -0400, Joel Fernandes wrote: > On Sun, Mar 15, 2020 at 07:18:36PM +0100, Uladzislau Rezki (Sony) wrote: > > kvfree_rcu() can deal with an allocated memory that is obtained > > via kvmalloc(). It can return two types of allocated memory or > > "pointers", one can belong to regular SLAB allocator and another > > one can be vmalloc one. It depends on requested size and memory > > pressure. > > > > Based on that, two streams are split, thus if a pointer belongs > > to vmalloc allocator it is queued to the list, otherwise SLAB > > one is queued into "bulk array" for further processing. > > > > The main reason of such splitting is: > > a) to distinguish kmalloc()/vmalloc() ptrs; > > b) there is no vmalloc_bulk() interface. > > > > As of now we have list_lru.c user that needs such interface, > > also there will be new comers. Apart of that it is preparation > > to have a head-less variant later. > > > > Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> > > --- > > include/linux/rcupdate.h | 9 +++++++++ > > kernel/rcu/tiny.c | 3 ++- > > kernel/rcu/tree.c | 17 ++++++++++++----- > > 3 files changed, 23 insertions(+), 6 deletions(-) > > > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > > index 2be97a83f266..bb270221dbdc 100644 > > --- a/include/linux/rcupdate.h > > +++ b/include/linux/rcupdate.h > > @@ -845,6 +845,15 @@ do { \ > > __kfree_rcu(&((___p)->rhf), offsetof(typeof(*(ptr)), rhf)); \ > > } while (0) > > > > +/** > > + * kvfree_rcu() - kvfree an object after a grace period. > > + * @ptr: pointer to kvfree > > + * @rhf: the name of the struct rcu_head within the type of @ptr. > > + * > > + * Same as kfree_rcu(), just simple alias. > > + */ > > +#define kvfree_rcu(ptr, rhf) kfree_rcu(ptr, rhf) > > + > > /* > > * Place this after a lock-acquisition primitive to guarantee that > > * an UNLOCK+LOCK pair acts as a full barrier. This guarantee applies > > diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c > > index dd572ce7c747..4b99f7b88bee 100644 > > --- a/kernel/rcu/tiny.c > > +++ b/kernel/rcu/tiny.c > > @@ -23,6 +23,7 @@ > > #include <linux/cpu.h> > > #include <linux/prefetch.h> > > #include <linux/slab.h> > > +#include <linux/mm.h> > > > > #include "rcu.h" > > > > @@ -86,7 +87,7 @@ static inline bool rcu_reclaim_tiny(struct rcu_head *head) > > rcu_lock_acquire(&rcu_callback_map); > > if (__is_kfree_rcu_offset(offset)) { > > trace_rcu_invoke_kfree_callback("", head, offset); > > - kfree((void *)head - offset); > > + kvfree((void *)head - offset); > > rcu_lock_release(&rcu_callback_map); > > return true; > > } > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 2f4c91a3713a..1c0a73616872 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -2899,9 +2899,9 @@ static void kfree_rcu_work(struct work_struct *work) > > } > > > > /* > > - * Emergency case only. It can happen under low memory > > - * condition when an allocation gets failed, so the "bulk" > > - * path can not be temporary maintained. > > + * vmalloc() pointers end up here also emergency case. It can > > Suggest rephrase for clarity: > > nit: We can end up here either with 1) vmalloc() pointers or 2) low on memory > and could not allocate a bulk array. > Let's go with your suggestion. I see that you took patches to your tree. Could you please update it on your own? Otherwise i can send out V2, so please let me know.
Thanks for the comments!
-- Vlad Rezki
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