| Message ID | 20220818131042.113280-11-aneesh.kumar@linux.ibm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/demotion: Memory tiers and demotion | expand |
Hi Aneesh, Please CC maintainers in your recipient list. On Thu, Aug 18, 2022 at 06:40:42PM +0530, Aneesh Kumar K.V wrote: > The most common case for certain node_random usage (demotion nodemask) is with > nodemask weight 1. We can avoid calling get_random_init() in that case and > always return the only node set in the nodemask. Can you move the comment about get_random_int() to the code?. > A simple test as below > before = rdtsc_ordered(); > for (i= 0; i < 100; i++) { > rand = node_random(&nmask); > } > after = rdtsc_ordered(); > > Without fix after - before : 16438 > With fix after - before : 816 > > Reviewed-by: "Huang, Ying" <ying.huang@intel.com> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > --- > include/linux/nodemask.h | 15 ++++++++++++--- > 1 file changed, 12 insertions(+), 3 deletions(-) > > diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h > index 4b71a96190a8..ac5b6a371be5 100644 > --- a/include/linux/nodemask.h > +++ b/include/linux/nodemask.h > @@ -504,12 +504,21 @@ static inline int num_node_state(enum node_states state) > static inline int node_random(const nodemask_t *maskp) > { > #if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1) > - int w, bit = NUMA_NO_NODE; > + int w, bit; > > w = nodes_weight(*maskp); > - if (w) > + switch (w) { > + case 0: > + bit = NUMA_NO_NODE; > + break; Why not 'return NUMA_NO_NODE' instead of break thing? > + case 1: > + bit = first_node(*maskp); > + break; > + default: > bit = bitmap_ord_to_pos(maskp->bits, > - get_random_int() % w, MAX_NUMNODES); > + get_random_int() % w, MAX_NUMNODES); Don't fix tabs - it trashes the history. > + break; > + } > return bit; > #else > return 0; > -- > 2.37.2 > >
diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h index 4b71a96190a8..ac5b6a371be5 100644 --- a/include/linux/nodemask.h +++ b/include/linux/nodemask.h @@ -504,12 +504,21 @@ static inline int num_node_state(enum node_states state) static inline int node_random(const nodemask_t *maskp) { #if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1) - int w, bit = NUMA_NO_NODE; + int w, bit; w = nodes_weight(*maskp); - if (w) + switch (w) { + case 0: + bit = NUMA_NO_NODE; + break; + case 1: + bit = first_node(*maskp); + break; + default: bit = bitmap_ord_to_pos(maskp->bits, - get_random_int() % w, MAX_NUMNODES); + get_random_int() % w, MAX_NUMNODES); + break; + } return bit; #else return 0;
The most common case for certain node_random usage (demotion nodemask) is with nodemask weight 1. We can avoid calling get_random_init() in that case and always return the only node set in the nodemask. A simple test as below before = rdtsc_ordered(); for (i= 0; i < 100; i++) { rand = node_random(&nmask); } after = rdtsc_ordered(); Without fix after - before : 16438 With fix after - before : 816 Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> --- include/linux/nodemask.h | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)