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From:   SeongJae Park <sj@kernel.org>
Cc:     sj@kernel.org, akpm@linux-foundation.org, damon@lists.linux.dev,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        xhao@linux.alibaba.com
Subject: Re: [PATCH] mm/damon: Remove duplicate get_monitoring_region() definitions
Date:   Wed,  7 Sep 2022 17:27:12 +0000
Message-Id: <20220907172712.61006-1-sj@kernel.org>
In-Reply-To: <20220907112924.65546-1-xhao@linux.alibaba.com>
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Hi Xin,

> In lru_sort.c and reclaim.c, they are all define get_monitoring_region()

s/define/defining/

> function, there is no need to define it separately.

Good point!

> 
> BTW, this patch remove tow struct 'damon_lru_sort_ram_walk_arg' and

s/remove/removes/
s/tow/two/

> 'damon_reclaim_ram_walk_arg', though the two struct are removed, if we
> want to add more fields to these struct for other purposes later, it will

s/struct/structs/

> not too late for us to use them again.
> For example:
>     struct damon_reclaim_ram_walk_arg {
> 	struct damon_addr_range raw_walk;
> 	xxx  A;
> 	xxx  B;
>     }
>     struct damon_lru_sort_ram_walk_arg {
> 	struct damon_addr_range raw_walk;
> 	xxx  A;
> 	xxx  B;
>     }

I haven't read the below part yet, but seems you're gonna use 'struct
damon_addr_range' instead of 'struct damon_{reclai,lru_sort}_ram_walk_arg'.

And I think we have already discussed about this before:
https://lore.kernel.org/damon/20220818172322.51705-1-sj@kernel.org/

My point is, we might add some more fileds to 'struct damon_addr_range' in a
future, though it seems very unlikely at the moment.  Sorry for not making my
opinion clear enough.

> 
> Signed-off-by: Xin Hao <xhao@linux.alibaba.com>
> ---
>  mm/damon/lru_sort.c   | 35 ++---------------------------------
>  mm/damon/ops-common.c | 28 ++++++++++++++++++++++++++++
>  mm/damon/ops-common.h |  1 +
>  mm/damon/reclaim.c    | 35 ++---------------------------------
>  4 files changed, 33 insertions(+), 66 deletions(-)
> 
> diff --git a/mm/damon/lru_sort.c b/mm/damon/lru_sort.c
> index 9de6f00a71c5..5032d59d46e4 100644
> --- a/mm/damon/lru_sort.c
> +++ b/mm/damon/lru_sort.c
> @@ -13,6 +13,8 @@
>  #include <linux/sched.h>
>  #include <linux/workqueue.h>
> 
> +#include "ops-common.h"
> +
>  #ifdef MODULE_PARAM_PREFIX
>  #undef MODULE_PARAM_PREFIX
>  #endif
> @@ -257,39 +259,6 @@ module_param(nr_cold_quota_exceeds, ulong, 0400);
>  static struct damon_ctx *ctx;
>  static struct damon_target *target;
> 
> -struct damon_lru_sort_ram_walk_arg {
> -	unsigned long start;
> -	unsigned long end;
> -};
> -
> -static int walk_system_ram(struct resource *res, void *arg)
> -{
> -	struct damon_lru_sort_ram_walk_arg *a = arg;
> -
> -	if (a->end - a->start < resource_size(res)) {
> -		a->start = res->start;
> -		a->end = res->end;
> -	}
> -	return 0;
> -}
> -
> -/*
> - * Find biggest 'System RAM' resource and store its start and end address in
> - * @start and @end, respectively.  If no System RAM is found, returns false.
> - */
> -static bool get_monitoring_region(unsigned long *start, unsigned long *end)
> -{
> -	struct damon_lru_sort_ram_walk_arg arg = {};
> -
> -	walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
> -	if (arg.end <= arg.start)
> -		return false;
> -
> -	*start = arg.start;
> -	*end = arg.end;
> -	return true;
> -}
> -
>  /* Create a DAMON-based operation scheme for hot memory regions */
>  static struct damos *damon_lru_sort_new_hot_scheme(unsigned int hot_thres)
>  {
> diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
> index b1335de200e7..01938f33038d 100644
> --- a/mm/damon/ops-common.c
> +++ b/mm/damon/ops-common.c
> @@ -172,3 +172,31 @@ int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
> 
>  	return hotness;
>  }
> +
> +static inline int walk_system_ram(struct resource *res, void *arg)
> +{
> +	struct damon_addr_range *a = arg;
> +
> +	if (a->end - a->start < resource_size(res)) {
> +		a->start = res->start;
> +		a->end = res->end;
> +	}
> +	return 0;
> +}
> +
> +/*
> + * Find biggest 'System RAM' resource and store its start and end address in
> + * @start and @end, respectively.  If no System RAM is found, returns false.
> + */
> +bool get_monitoring_region(unsigned long *start, unsigned long *end)
> +{
> +	struct damon_addr_range arg = {};
> +
> +	walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
> +	if (arg.end <= arg.start)
> +		return false;
> +
> +	*start = arg.start;
> +	*end = arg.end;
> +	return true;
> +}

'ops-common.c' is for code that common in monitoring operations
implementations.  I'd prefer to have yet another source file for the DAMON
modules including reclaim and lru_sort, say, 'modules-common.c'.

Also, as 'get_monitoring_region()' is not a 'static' function anymore, let's
have a prefix to distinguish with other functions, say, 'damon_modules_'?

> diff --git a/mm/damon/ops-common.h b/mm/damon/ops-common.h
> index 52329ff361cd..e6f1c9b48042 100644
> --- a/mm/damon/ops-common.h
> +++ b/mm/damon/ops-common.h
> @@ -16,3 +16,4 @@ int damon_pageout_score(struct damon_ctx *c, struct damon_region *r,
>  			struct damos *s);
>  int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
>  			struct damos *s);
> +bool get_monitoring_region(unsigned long *start, unsigned long *end);

Let's move it to a dedicated source file, say, 'modules-common.h'

> diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
> index a7faf51b4bd4..20e83eee3c7d 100644
> --- a/mm/damon/reclaim.c
> +++ b/mm/damon/reclaim.c
> @@ -13,6 +13,8 @@
>  #include <linux/sched.h>
>  #include <linux/workqueue.h>
> 
> +#include "ops-common.h"
> +
>  #ifdef MODULE_PARAM_PREFIX
>  #undef MODULE_PARAM_PREFIX
>  #endif
> @@ -229,39 +231,6 @@ module_param(nr_quota_exceeds, ulong, 0400);
>  static struct damon_ctx *ctx;
>  static struct damon_target *target;
> 
> -struct damon_reclaim_ram_walk_arg {
> -	unsigned long start;
> -	unsigned long end;
> -};
> -
> -static int walk_system_ram(struct resource *res, void *arg)
> -{
> -	struct damon_reclaim_ram_walk_arg *a = arg;
> -
> -	if (a->end - a->start < resource_size(res)) {
> -		a->start = res->start;
> -		a->end = res->end;
> -	}
> -	return 0;
> -}
> -
> -/*
> - * Find biggest 'System RAM' resource and store its start and end address in
> - * @start and @end, respectively.  If no System RAM is found, returns false.
> - */
> -static bool get_monitoring_region(unsigned long *start, unsigned long *end)
> -{
> -	struct damon_reclaim_ram_walk_arg arg = {};
> -
> -	walk_system_ram_res(0, ULONG_MAX, &arg, walk_system_ram);
> -	if (arg.end <= arg.start)
> -		return false;
> -
> -	*start = arg.start;
> -	*end = arg.end;
> -	return true;
> -}
> -
>  static struct damos *damon_reclaim_new_scheme(void)
>  {
>  	struct damos_watermarks wmarks = {
> --
> 2.31.0


Thanks,
SJ