| Message ID | 20230412143127.1062367-1-qiang1.zhang@intel.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c1c4f33b6be9b3412d9e0ba01b367f4ffe47c379 |
| Headers | show |
| Series | rcu/kvfree: Make fill page cache start from krcp->nr_bkv_objs | expand |
On Wed, Apr 12, 2023 at 10:31:27PM +0800, Zqiang wrote: > The fill_page_cache_func() is invoked and start from zero to > allocate nr_pages of page, if the kfree_rcu_work() executes before > the fill_page_cache_func(), the krcp->nr_bkv_objs is updated before > enter for-loop and equal to nr_pages, since the page is allocated > first, and then check the krcp->nr_bkv_objs in put_cached_bnode(), > this produces a meaningless __get_free_page() call, this commit > therefore make allocate page start from krcp->nr_bkv_objs and > check krcp->nr_bkv_objs before allocate page. > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > --- > kernel/rcu/tree.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 41daae3239b5..dcb86f9f2dd6 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3223,7 +3223,7 @@ static void fill_page_cache_func(struct work_struct *work) > nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ? > 1 : rcu_min_cached_objs; > > - for (i = 0; i < nr_pages; i++) { > + for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) { > bnode = (struct kvfree_rcu_bulk_data *) > __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); > > -- > 2.32.0 > Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com> -- Uladzislau Rezki
On Thu, Apr 13, 2023 at 11:07:09AM +0200, Uladzislau Rezki wrote: > On Wed, Apr 12, 2023 at 10:31:27PM +0800, Zqiang wrote: > > The fill_page_cache_func() is invoked and start from zero to > > allocate nr_pages of page, if the kfree_rcu_work() executes before > > the fill_page_cache_func(), the krcp->nr_bkv_objs is updated before > > enter for-loop and equal to nr_pages, since the page is allocated > > first, and then check the krcp->nr_bkv_objs in put_cached_bnode(), > > this produces a meaningless __get_free_page() call, this commit > > therefore make allocate page start from krcp->nr_bkv_objs and > > check krcp->nr_bkv_objs before allocate page. > > > > Signed-off-by: Zqiang <qiang1.zhang@intel.com> > > --- > > kernel/rcu/tree.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 41daae3239b5..dcb86f9f2dd6 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > > @@ -3223,7 +3223,7 @@ static void fill_page_cache_func(struct work_struct *work) > > nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ? > > 1 : rcu_min_cached_objs; > > > > - for (i = 0; i < nr_pages; i++) { > > + for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) { > > bnode = (struct kvfree_rcu_bulk_data *) > > __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); > > > > -- > > 2.32.0 > > > Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Queued and pushed, thank you both! Thanx, Paul
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 41daae3239b5..dcb86f9f2dd6 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3223,7 +3223,7 @@ static void fill_page_cache_func(struct work_struct *work) nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ? 1 : rcu_min_cached_objs; - for (i = 0; i < nr_pages; i++) { + for (i = READ_ONCE(krcp->nr_bkv_objs); i < nr_pages; i++) { bnode = (struct kvfree_rcu_bulk_data *) __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
The fill_page_cache_func() is invoked and start from zero to allocate nr_pages of page, if the kfree_rcu_work() executes before the fill_page_cache_func(), the krcp->nr_bkv_objs is updated before enter for-loop and equal to nr_pages, since the page is allocated first, and then check the krcp->nr_bkv_objs in put_cached_bnode(), this produces a meaningless __get_free_page() call, this commit therefore make allocate page start from krcp->nr_bkv_objs and check krcp->nr_bkv_objs before allocate page. Signed-off-by: Zqiang <qiang1.zhang@intel.com> --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)