| Message ID | 20220630094646.91837-3-haibo.li@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ANDROID: cfi:free old cfi shadow asynchronously | expand |
Hi, On Thu, Jun 30, 2022 at 2:47 AM Haibo Li <haibo.li@mediatek.com> wrote: > > Currenly, it uses synchronize_rcu() to wait old rcu reader to go away > in update_shadow.In embedded platform like ARM CA7X, > load_module blocks 40~50ms in update_shadow. > When there are more than one hundred kernel modules, > it blocks several seconds. > > To accelerate load_module,change synchronize_rcu to call_rcu. > > Signed-off-by: Haibo Li <haibo.li@mediatek.com> > Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com> Thanks for the patch! Please drop ANDROID: from the subject line, that's only used in the Android kernel trees. > kernel/cfi.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/kernel/cfi.c b/kernel/cfi.c > index 456771c8e454..a4836d59ca27 100644 > --- a/kernel/cfi.c > +++ b/kernel/cfi.c > @@ -43,6 +43,8 @@ typedef u16 shadow_t; > struct cfi_shadow { > /* Page index for the beginning of the shadow */ > unsigned long base; > + /* rcu to free old cfi_shadow asynchronously */ > + struct rcu_head rcu; > /* An array of __cfi_check locations (as indices to the shadow) */ > shadow_t shadow[1]; > } __packed; > @@ -182,6 +184,13 @@ static void remove_module_from_shadow(struct cfi_shadow *s, struct module *mod, > } > } > > +static void _cfi_shadow_free_rcu(struct rcu_head *rcu) I think this can be simply renamed to free_shadow. > +{ > + struct cfi_shadow *old = container_of(rcu, struct cfi_shadow, rcu); > + > + vfree(old); > +} > + > typedef void (*update_shadow_fn)(struct cfi_shadow *, struct module *, > unsigned long min_addr, unsigned long max_addr); > > @@ -211,11 +220,10 @@ static void update_shadow(struct module *mod, unsigned long base_addr, > > rcu_assign_pointer(cfi_shadow, next); > mutex_unlock(&shadow_update_lock); > - synchronize_rcu(); > > if (prev) { > set_memory_rw((unsigned long)prev, SHADOW_PAGES); > - vfree(prev); > + call_rcu(&prev->rcu, _cfi_shadow_free_rcu); > } > } It's probably better to keep the pages read-only until they're actually released. Can you move the set_memory_rw call to the new function? Sami
> Hi, > > On Thu, Jun 30, 2022 at 2:47 AM Haibo Li <haibo.li@mediatek.com> wrote: > > > > Currenly, it uses synchronize_rcu() to wait old rcu reader to go away > > in update_shadow.In embedded platform like ARM CA7X, load_module > > blocks 40~50ms in update_shadow. > > When there are more than one hundred kernel modules, it blocks several > > seconds. > > > > To accelerate load_module,change synchronize_rcu to call_rcu. > > > > Signed-off-by: Haibo Li <haibo.li@mediatek.com> > > Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com> > > Thanks for the patch! Please drop ANDROID: from the subject line, that's only > used in the Android kernel trees. > Thanks for the comment.I will change it in next patch. > > kernel/cfi.c | 12 ++++++++++-- > > 1 file changed, 10 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/cfi.c b/kernel/cfi.c index > > 456771c8e454..a4836d59ca27 100644 > > --- a/kernel/cfi.c > > +++ b/kernel/cfi.c > > @@ -43,6 +43,8 @@ typedef u16 shadow_t; struct cfi_shadow { > > /* Page index for the beginning of the shadow */ > > unsigned long base; > > + /* rcu to free old cfi_shadow asynchronously */ > > + struct rcu_head rcu; > > /* An array of __cfi_check locations (as indices to the shadow) */ > > shadow_t shadow[1]; > > } __packed; > > @@ -182,6 +184,13 @@ static void remove_module_from_shadow(struct > cfi_shadow *s, struct module *mod, > > } > > } > > > > +static void _cfi_shadow_free_rcu(struct rcu_head *rcu) > > I think this can be simply renamed to free_shadow. Thanks for the comment.I will change it in next patch. > > > +{ > > + struct cfi_shadow *old = container_of(rcu, struct cfi_shadow, > > +rcu); > > + > > + vfree(old); > > +} > > + > > typedef void (*update_shadow_fn)(struct cfi_shadow *, struct module *, > > unsigned long min_addr, unsigned long > > max_addr); > > > > @@ -211,11 +220,10 @@ static void update_shadow(struct module *mod, > > unsigned long base_addr, > > > > rcu_assign_pointer(cfi_shadow, next); > > mutex_unlock(&shadow_update_lock); > > - synchronize_rcu(); > > > > if (prev) { > > set_memory_rw((unsigned long)prev, SHADOW_PAGES); > > - vfree(prev); > > + call_rcu(&prev->rcu, _cfi_shadow_free_rcu); > > } > > } > > It's probably better to keep the pages read-only until they're actually released. > Can you move the set_memory_rw call to the new function? > Since call_rcu and rcu callbacks change members in &prev->rcu,the old pages need to be rw at first.
diff --git a/kernel/cfi.c b/kernel/cfi.c index 456771c8e454..a4836d59ca27 100644 --- a/kernel/cfi.c +++ b/kernel/cfi.c @@ -43,6 +43,8 @@ typedef u16 shadow_t; struct cfi_shadow { /* Page index for the beginning of the shadow */ unsigned long base; + /* rcu to free old cfi_shadow asynchronously */ + struct rcu_head rcu; /* An array of __cfi_check locations (as indices to the shadow) */ shadow_t shadow[1]; } __packed; @@ -182,6 +184,13 @@ static void remove_module_from_shadow(struct cfi_shadow *s, struct module *mod, } } +static void _cfi_shadow_free_rcu(struct rcu_head *rcu) +{ + struct cfi_shadow *old = container_of(rcu, struct cfi_shadow, rcu); + + vfree(old); +} + typedef void (*update_shadow_fn)(struct cfi_shadow *, struct module *, unsigned long min_addr, unsigned long max_addr); @@ -211,11 +220,10 @@ static void update_shadow(struct module *mod, unsigned long base_addr, rcu_assign_pointer(cfi_shadow, next); mutex_unlock(&shadow_update_lock); - synchronize_rcu(); if (prev) { set_memory_rw((unsigned long)prev, SHADOW_PAGES); - vfree(prev); + call_rcu(&prev->rcu, _cfi_shadow_free_rcu); } }