| Message ID | 20220416074059.526970-1-vvghjk1234@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] mm/slub: Remove repeated action in calculate_order() | expand |
On Sat, Apr 16, 2022 at 04:40:59PM +0900, Wonhyuk Yang wrote: > To calculate order, calc_slab_order() is called repeatly changing the > fract_leftover. Thus, the branch which is not dependent on > fract_leftover is executed repeatly. So make it run only once. > > Plus, when min_object reached to 0, we set fract_leftover to 1. In Maybe you mean when min_object reached 1. > this case, we can calculate order by max(slub_min_order, > get_order(size)) instead of calling calc_slab_order(). > > No functional impact expected. > Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com> > --- > V1 -> V2: Fix typo miss in a commit message > > mm/slub.c | 18 +++++++----------- > 1 file changed, 7 insertions(+), 11 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index ed5c2c03a47a..e7a394d7b75a 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3795,9 +3795,6 @@ static inline unsigned int calc_slab_order(unsigned int size, > unsigned int min_order = slub_min_order; > unsigned int order; > > - if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE) > - return get_order(size * MAX_OBJS_PER_PAGE) - 1; > - > for (order = max(min_order, (unsigned int)get_order(min_objects * size)); > order <= max_order; order++) { > > @@ -3820,6 +3817,11 @@ static inline int calculate_order(unsigned int size) > unsigned int max_objects; > unsigned int nr_cpus; > > + if (unlikely(order_objects(slub_min_order, size) > MAX_OBJS_PER_PAGE)) { > + order = get_order(size * MAX_OBJS_PER_PAGE) - 1; > + goto out; > + } > + > /* > * Attempt to find best configuration for a slab. This > * works by first attempting to generate a layout with > @@ -3865,14 +3867,8 @@ static inline int calculate_order(unsigned int size) > * We were unable to place multiple objects in a slab. Now > * lets see if we can place a single object there. > */ > - order = calc_slab_order(size, 1, slub_max_order, 1); > - if (order <= slub_max_order) > - return order; > - > - /* > - * Doh this slab cannot be placed using slub_max_order. > - */ > - order = calc_slab_order(size, 1, MAX_ORDER, 1); > + order = max_t(unsigned int, slub_min_order, (unsigned int)get_order(size)); > +out: You don't need to cast value of get_order(size). max_t() does cast both operands. > if (order < MAX_ORDER) > return order; > return -ENOSYS; For the correctness of the patch, I don't see any problem about the code. But to be honest I'm a bit skeptical about saving some cycles in calculating slab order. It's done only when creating caches (usually in boot process). > -- > 2.30.2 > >
On Sun, Apr 17, 2022 at 10:43:20AM +0900, Hyeonggon Yoo wrote: > On Sat, Apr 16, 2022 at 04:40:59PM +0900, Wonhyuk Yang wrote: > > To calculate order, calc_slab_order() is called repeatly changing the > > fract_leftover. Thus, the branch which is not dependent on > > fract_leftover is executed repeatly. So make it run only once. > > > > Plus, when min_object reached to 0, we set fract_leftover to 1. In > > Maybe you mean when min_object reached 1. > > > this case, we can calculate order by max(slub_min_order, > > get_order(size)) instead of calling calc_slab_order(). > > > > No functional impact expected. > > Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com> > > --- > > V1 -> V2: Fix typo miss in a commit message > > > > mm/slub.c | 18 +++++++----------- > > 1 file changed, 7 insertions(+), 11 deletions(-) > > > > diff --git a/mm/slub.c b/mm/slub.c > > index ed5c2c03a47a..e7a394d7b75a 100644 > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -3795,9 +3795,6 @@ static inline unsigned int calc_slab_order(unsigned int size, > > unsigned int min_order = slub_min_order; > > unsigned int order; > > > > - if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE) > > - return get_order(size * MAX_OBJS_PER_PAGE) - 1; > > - > > for (order = max(min_order, (unsigned int)get_order(min_objects * size)); > > order <= max_order; order++) { > > > > @@ -3820,6 +3817,11 @@ static inline int calculate_order(unsigned int size) > > unsigned int max_objects; > > unsigned int nr_cpus; > > > > + if (unlikely(order_objects(slub_min_order, size) > MAX_OBJS_PER_PAGE)) { > > + order = get_order(size * MAX_OBJS_PER_PAGE) - 1; > > + goto out; > > + } > > + > > /* > > * Attempt to find best configuration for a slab. This > > * works by first attempting to generate a layout with > > @@ -3865,14 +3867,8 @@ static inline int calculate_order(unsigned int size) > > * We were unable to place multiple objects in a slab. Now > > * lets see if we can place a single object there. > > */ > > - order = calc_slab_order(size, 1, slub_max_order, 1); > > - if (order <= slub_max_order) > > - return order; > > - > > - /* > > - * Doh this slab cannot be placed using slub_max_order. > > - */ > > - order = calc_slab_order(size, 1, MAX_ORDER, 1); > > + order = max_t(unsigned int, slub_min_order, (unsigned int)get_order(size)); > > +out: > > You don't need to cast value of get_order(size). max_t() does cast both operands. > > > if (order < MAX_ORDER) > > return order; > > return -ENOSYS; > > For the correctness of the patch, I don't see any problem about the > code. > > But to be honest I'm a bit skeptical about saving some cycles in > calculating slab order. It's done only when creating caches (usually in boot > process). But yeah, maybe it's worth for better maintenance of code. So after considering my comments, feel free to add: Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Thanks! > > -- > > 2.30.2 > > > > > > -- > Thanks, > Hyeonggon
On Sun, Apr 17, 2022 at 10:43 AM Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote: > > On Sat, Apr 16, 2022 at 04:40:59PM +0900, Wonhyuk Yang wrote: > > To calculate order, calc_slab_order() is called repeatly changing the > > fract_leftover. Thus, the branch which is not dependent on > > fract_leftover is executed repeatly. So make it run only once. > > > > Plus, when min_object reached to 0, we set fract_leftover to 1. In > > Maybe you mean when min_object reached 1. Yes, That comment need to be updated... > > > this case, we can calculate order by max(slub_min_order, > > get_order(size)) instead of calling calc_slab_order(). > > > > No functional impact expected. > > Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com> > > --- > > V1 -> V2: Fix typo miss in a commit message > > > > mm/slub.c | 18 +++++++----------- > > 1 file changed, 7 insertions(+), 11 deletions(-) > > > > diff --git a/mm/slub.c b/mm/slub.c > > index ed5c2c03a47a..e7a394d7b75a 100644 > > --- a/mm/slub.c > > +++ b/mm/slub.c > > @@ -3795,9 +3795,6 @@ static inline unsigned int calc_slab_order(unsigned int size, > > unsigned int min_order = slub_min_order; > > unsigned int order; > > > > - if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE) > > - return get_order(size * MAX_OBJS_PER_PAGE) - 1; > > - > > for (order = max(min_order, (unsigned int)get_order(min_objects * size)); > > order <= max_order; order++) { > > > > @@ -3820,6 +3817,11 @@ static inline int calculate_order(unsigned int size) > > unsigned int max_objects; > > unsigned int nr_cpus; > > > > + if (unlikely(order_objects(slub_min_order, size) > MAX_OBJS_PER_PAGE)) { > > + order = get_order(size * MAX_OBJS_PER_PAGE) - 1; > > + goto out; > > + } > > + > > /* > > * Attempt to find best configuration for a slab. This > > * works by first attempting to generate a layout with > > @@ -3865,14 +3867,8 @@ static inline int calculate_order(unsigned int size) > > * We were unable to place multiple objects in a slab. Now > > * lets see if we can place a single object there. > > */ > > - order = calc_slab_order(size, 1, slub_max_order, 1); > > - if (order <= slub_max_order) > > - return order; > > - > > - /* > > - * Doh this slab cannot be placed using slub_max_order. > > - */ > > - order = calc_slab_order(size, 1, MAX_ORDER, 1); > > + order = max_t(unsigned int, slub_min_order, (unsigned int)get_order(size)); > > +out: > > You don't need to cast value of get_order(size). max_t() does cast both operands. That's a good point, I will delete it. > > > if (order < MAX_ORDER) > > return order; > > return -ENOSYS; > > For the correctness of the patch, I don't see any problem about the > code. > > But to be honest I'm a bit skeptical about saving some cycles in > calculating slab order. It's done only when creating caches (usually in boot > process). >
On Sun, Apr 17, 2022 at 11:07 AM Hyeonggon Yoo <42.hyeyoo@gmail.com> wrote: > > On Sun, Apr 17, 2022 at 10:43:20AM +0900, Hyeonggon Yoo wrote: > > On Sat, Apr 16, 2022 at 04:40:59PM +0900, Wonhyuk Yang wrote: > > > To calculate order, calc_slab_order() is called repeatly changing the > > > fract_leftover. Thus, the branch which is not dependent on > > > fract_leftover is executed repeatly. So make it run only once. > > > > > > Plus, when min_object reached to 0, we set fract_leftover to 1. In > > > > Maybe you mean when min_object reached 1. > > > > > this case, we can calculate order by max(slub_min_order, > > > get_order(size)) instead of calling calc_slab_order(). > > > > > > No functional impact expected. > > > Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com> > > > --- > > > V1 -> V2: Fix typo miss in a commit message > > > > > > mm/slub.c | 18 +++++++----------- > > > 1 file changed, 7 insertions(+), 11 deletions(-) > > > > > > diff --git a/mm/slub.c b/mm/slub.c > > > index ed5c2c03a47a..e7a394d7b75a 100644 > > > --- a/mm/slub.c > > > +++ b/mm/slub.c > > > @@ -3795,9 +3795,6 @@ static inline unsigned int calc_slab_order(unsigned int size, > > > unsigned int min_order = slub_min_order; > > > unsigned int order; > > > > > > - if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE) > > > - return get_order(size * MAX_OBJS_PER_PAGE) - 1; > > > - > > > for (order = max(min_order, (unsigned int)get_order(min_objects * size)); > > > order <= max_order; order++) { > > > > > > @@ -3820,6 +3817,11 @@ static inline int calculate_order(unsigned int size) > > > unsigned int max_objects; > > > unsigned int nr_cpus; > > > > > > + if (unlikely(order_objects(slub_min_order, size) > MAX_OBJS_PER_PAGE)) { > > > + order = get_order(size * MAX_OBJS_PER_PAGE) - 1; > > > + goto out; > > > + } > > > + > > > /* > > > * Attempt to find best configuration for a slab. This > > > * works by first attempting to generate a layout with > > > @@ -3865,14 +3867,8 @@ static inline int calculate_order(unsigned int size) > > > * We were unable to place multiple objects in a slab. Now > > > * lets see if we can place a single object there. > > > */ > > > - order = calc_slab_order(size, 1, slub_max_order, 1); > > > - if (order <= slub_max_order) > > > - return order; > > > - > > > - /* > > > - * Doh this slab cannot be placed using slub_max_order. > > > - */ > > > - order = calc_slab_order(size, 1, MAX_ORDER, 1); > > > + order = max_t(unsigned int, slub_min_order, (unsigned int)get_order(size)); > > > +out: > > > > You don't need to cast value of get_order(size). max_t() does cast both operands. > > > > > if (order < MAX_ORDER) > > > return order; > > > return -ENOSYS; > > > > For the correctness of the patch, I don't see any problem about the > > code. > > > > But to be honest I'm a bit skeptical about saving some cycles in > > calculating slab order. It's done only when creating caches (usually in boot > > process). > > But yeah, maybe it's worth for better maintenance of code. > > So after considering my comments, feel free to add: > Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> > > Thanks! > Thanks for taking the time to review Hyeonggon!
diff --git a/mm/slub.c b/mm/slub.c index ed5c2c03a47a..e7a394d7b75a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3795,9 +3795,6 @@ static inline unsigned int calc_slab_order(unsigned int size, unsigned int min_order = slub_min_order; unsigned int order; - if (order_objects(min_order, size) > MAX_OBJS_PER_PAGE) - return get_order(size * MAX_OBJS_PER_PAGE) - 1; - for (order = max(min_order, (unsigned int)get_order(min_objects * size)); order <= max_order; order++) { @@ -3820,6 +3817,11 @@ static inline int calculate_order(unsigned int size) unsigned int max_objects; unsigned int nr_cpus; + if (unlikely(order_objects(slub_min_order, size) > MAX_OBJS_PER_PAGE)) { + order = get_order(size * MAX_OBJS_PER_PAGE) - 1; + goto out; + } + /* * Attempt to find best configuration for a slab. This * works by first attempting to generate a layout with @@ -3865,14 +3867,8 @@ static inline int calculate_order(unsigned int size) * We were unable to place multiple objects in a slab. Now * lets see if we can place a single object there. */ - order = calc_slab_order(size, 1, slub_max_order, 1); - if (order <= slub_max_order) - return order; - - /* - * Doh this slab cannot be placed using slub_max_order. - */ - order = calc_slab_order(size, 1, MAX_ORDER, 1); + order = max_t(unsigned int, slub_min_order, (unsigned int)get_order(size)); +out: if (order < MAX_ORDER) return order; return -ENOSYS;
To calculate order, calc_slab_order() is called repeatly changing the fract_leftover. Thus, the branch which is not dependent on fract_leftover is executed repeatly. So make it run only once. Plus, when min_object reached to 0, we set fract_leftover to 1. In this case, we can calculate order by max(slub_min_order, get_order(size)) instead of calling calc_slab_order(). No functional impact expected. Signed-off-by: Wonhyuk Yang <vvghjk1234@gmail.com> --- V1 -> V2: Fix typo miss in a commit message mm/slub.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-)