Subject: Re: [RESEND PATCH 2/2] lib/nodemask: inline next_node_in() and node_random()

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Fri, 12 Aug 2022 10:46:57 +0530

Yury Norov <[email-masked]> writes:

> The functions are pretty thin wrappers around find_bit engine, and
> keeping them in c-file prevents compiler from small_const_nbits()
> optimization, which must take place for all systems with MAX_NUMNODES
> less than BITS_PER_LONG (default is 16 for me).
>
> Moving them to header file doesn't blow up the kernel size:
> add/remove: 1/2 grow/shrink: 9/5 up/down: 968/-88 (880)
>
> CC: Andy Shevchenko <[email-masked]>
> CC: Rasmus Villemoes <[email-masked]>
> Signed-off-by: Yury Norov <[email-masked]>
> ---
>  MAINTAINERS              |  1 -
>  include/linux/nodemask.h | 27 ++++++++++++++++++++++-----
>  lib/Makefile             |  2 +-
>  lib/nodemask.c           | 30 ------------------------------
>  4 files changed, 23 insertions(+), 37 deletions(-)
>  delete mode 100644 lib/nodemask.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 7c0b8f28aa25..19c8d0ef1177 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3540,7 +3540,6 @@ F:	lib/bitmap.c
>  F:	lib/cpumask.c
>  F:	lib/find_bit.c
>  F:	lib/find_bit_benchmark.c
> -F:	lib/nodemask.c
>  F:	lib/test_bitmap.c
>  F:	tools/include/linux/bitmap.h
>  F:	tools/include/linux/find.h
> diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> index 0f233b76c9ce..48ebe4007955 100644
> --- a/include/linux/nodemask.h
> +++ b/include/linux/nodemask.h
> @@ -94,6 +94,7 @@
>  #include <linux/bitmap.h>
>  #include <linux/minmax.h>
>  #include <linux/numa.h>
> +#include <linux/random.h>
>  
>  typedef struct { DECLARE_BITMAP(bits, MAX_NUMNODES); } nodemask_t;
>  extern nodemask_t _unused_nodemask_arg_;
> @@ -276,7 +277,14 @@ static inline unsigned int __next_node(int n, const nodemask_t *srcp)
>   * the first node in src if needed.  Returns MAX_NUMNODES if src is empty.
>   */
>  #define next_node_in(n, src) __next_node_in((n), &(src))
> -unsigned int __next_node_in(int node, const nodemask_t *srcp);
> +static inline unsigned int __next_node_in(int node, const nodemask_t *srcp)
> +{
> +	unsigned int ret = __next_node(node, srcp);
> +
> +	if (ret == MAX_NUMNODES)
> +		ret = __first_node(srcp);
> +	return ret;
> +}
>  
>  static inline void init_nodemask_of_node(nodemask_t *mask, int node)
>  {
> @@ -493,14 +501,23 @@ static inline int num_node_state(enum node_states state)
>  
>  #endif
>  
> +/*
> + * Return the bit number of a random bit set in the nodemask.
> + * (returns NUMA_NO_NODE if nodemask is empty)
> + */
> +static inline int node_random(const nodemask_t *maskp)
> +{
>  #if defined(CONFIG_NUMA) && (MAX_NUMNODES > 1)
> -extern int node_random(const nodemask_t *maskp);
> +	int w, bit = NUMA_NO_NODE;
> +
> +	w = nodes_weight(*maskp);
> +	if (w)
> +		bit = find_nth_bit(maskp->bits, MAX_NUMNODES, get_random_int() % w);
> +	return bit;
>  #else
> -static inline int node_random(const nodemask_t *mask)
> -{
>  	return 0;
> -}
>  #endif
> +}
>  
>  #define node_online_map 	node_states[N_ONLINE]
>  #define node_possible_map 	node_states[N_POSSIBLE]
> diff --git a/lib/Makefile b/lib/Makefile
> index f99bf61f8bbc..731cea0342d1 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -33,7 +33,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
>  	 flex_proportions.o ratelimit.o show_mem.o \
>  	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
>  	 earlycpio.o seq_buf.o siphash.o dec_and_lock.o \
> -	 nmi_backtrace.o nodemask.o win_minmax.o memcat_p.o \
> +	 nmi_backtrace.o win_minmax.o memcat_p.o \
>  	 buildid.o
>  
>  lib-$(CONFIG_PRINTK) += dump_stack.o
> diff --git a/lib/nodemask.c b/lib/nodemask.c
> deleted file mode 100644
> index 7dad4ce8ff59..000000000000
> --- a/lib/nodemask.c
> +++ /dev/null
> @@ -1,30 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0
> -#include <linux/nodemask.h>
> -#include <linux/module.h>
> -#include <linux/random.h>
> -
> -unsigned int __next_node_in(int node, const nodemask_t *srcp)
> -{
> -	unsigned int ret = __next_node(node, srcp);
> -
> -	if (ret == MAX_NUMNODES)
> -		ret = __first_node(srcp);
> -	return ret;
> -}
> -EXPORT_SYMBOL(__next_node_in);
> -
> -#ifdef CONFIG_NUMA
> -/*
> - * Return the bit number of a random bit set in the nodemask.
> - * (returns NUMA_NO_NODE if nodemask is empty)
> - */
> -int node_random(const nodemask_t *maskp)
> -{
> -	int w, bit = NUMA_NO_NODE;
> -
> -	w = nodes_weight(*maskp);
> -	if (w)
> -		bit = find_nth_bit(maskp->bits, MAX_NUMNODES, get_random_int() % w);
> -	return bit;
> -}
> -#endif
> -- 
> 2.34.1

The patch that got merged (36d4b36b69590fed99356a4426c940a253a93800) still have lib/nodemask.c