Re: [PATCH v4 1/9] hugetlb_cgroup: Add hugetlb_cgroup reservation counter

[shuah <shuah@kernel.org>]

On 9/10/19 5:31 PM, Mina Almasry wrote:
> These counters will track hugetlb reservations rather than hugetlb
> memory faulted in. This patch only adds the counter, following patches
> add the charging and uncharging of the counter.
> 

Why are we adding these counters? I see the reasons in the cover letter.
Why not add the details on why this is needed here in this commitlog

Please add more information on why and rephrase the commit log.

> Signed-off-by: Mina Almasry <almasrymina@google.com>
> Acked-by: Hillf Danton <hdanton@sina.com>
> ---
>   include/linux/hugetlb.h |  16 +++++-
>   mm/hugetlb_cgroup.c     | 111 ++++++++++++++++++++++++++++++----------
>   2 files changed, 100 insertions(+), 27 deletions(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index edfca42783192..128ff1aff1c93 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -320,6 +320,20 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
> 
>   #ifdef CONFIG_HUGETLB_PAGE
> 
> +enum {
> +	HUGETLB_RES_USAGE,
> +	HUGETLB_RES_RESERVATION_USAGE,
> +	HUGETLB_RES_LIMIT,
> +	HUGETLB_RES_RESERVATION_LIMIT,
> +	HUGETLB_RES_MAX_USAGE,
> +	HUGETLB_RES_RESERVATION_MAX_USAGE,
> +	HUGETLB_RES_FAILCNT,
> +	HUGETLB_RES_RESERVATION_FAILCNT,
> +	HUGETLB_RES_NULL,
> +	HUGETLB_RES_MAX,
> +};
> +

Please add information on what these track. As an example
HUGETLB_RES_RESERVATION_LIMIT is so close to HUGETLB_RES_LIMIT

What are we tracking and measuring?

> +
>   #define HSTATE_NAME_LEN 32
>   /* Defines one hugetlb page size */
>   struct hstate {
> @@ -340,7 +354,7 @@ struct hstate {
>   	unsigned int surplus_huge_pages_node[MAX_NUMNODES];
>   #ifdef CONFIG_CGROUP_HUGETLB
>   	/* cgroup control files */
> -	struct cftype cgroup_files[5];
> +	struct cftype cgroup_files[HUGETLB_RES_MAX];
>   #endif
>   	char name[HSTATE_NAME_LEN];
>   };
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index 68c2f2f3c05b7..51a72624bd1ff 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -25,6 +25,10 @@ struct hugetlb_cgroup {
>   	 * the counter to account for hugepages from hugetlb.
>   	 */
>   	struct page_counter hugepage[HUGE_MAX_HSTATE];
> +	/*
> +	 * the counter to account for hugepage reservations from hugetlb.
> +	 */
> +	struct page_counter reserved_hugepage[HUGE_MAX_HSTATE];
>   };
> 
>   #define MEMFILE_PRIVATE(x, val)	(((x) << 16) | (val))
> @@ -33,6 +37,15 @@ struct hugetlb_cgroup {
> 
>   static struct hugetlb_cgroup *root_h_cgroup __read_mostly;
> 
> +static inline
> +struct page_counter *hugetlb_cgroup_get_counter(struct hugetlb_cgroup *h_cg, int idx,
> +				 bool reserved)
> +{
> +	if (reserved)
> +		return  &h_cg->reserved_hugepage[idx];
> +	return &h_cg->hugepage[idx];
> +}
> +
>   static inline
>   struct hugetlb_cgroup *hugetlb_cgroup_from_css(struct cgroup_subsys_state *s)
>   {
> @@ -254,30 +267,33 @@ void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
>   	return;
>   }
> 
> -enum {
> -	RES_USAGE,
> -	RES_LIMIT,
> -	RES_MAX_USAGE,
> -	RES_FAILCNT,
> -};
> -
>   static u64 hugetlb_cgroup_read_u64(struct cgroup_subsys_state *css,
>   				   struct cftype *cft)
>   {
>   	struct page_counter *counter;
> +	struct page_counter *reserved_counter;
>   	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(css);
> 
>   	counter = &h_cg->hugepage[MEMFILE_IDX(cft->private)];
> +	reserved_counter = &h_cg->reserved_hugepage[MEMFILE_IDX(cft->private)];
> 
>   	switch (MEMFILE_ATTR(cft->private)) {
> -	case RES_USAGE:
> +	case HUGETLB_RES_USAGE:
>   		return (u64)page_counter_read(counter) * PAGE_SIZE;
> -	case RES_LIMIT:
> +	case HUGETLB_RES_RESERVATION_USAGE:
> +		return (u64)page_counter_read(reserved_counter) * PAGE_SIZE;
> +	case HUGETLB_RES_LIMIT:
>   		return (u64)counter->max * PAGE_SIZE;
> -	case RES_MAX_USAGE:
> +	case HUGETLB_RES_RESERVATION_LIMIT:
> +		return (u64)reserved_counter->max * PAGE_SIZE;
> +	case HUGETLB_RES_MAX_USAGE:
>   		return (u64)counter->watermark * PAGE_SIZE;
> -	case RES_FAILCNT:
> +	case HUGETLB_RES_RESERVATION_MAX_USAGE:
> +		return (u64)reserved_counter->watermark * PAGE_SIZE;
> +	case HUGETLB_RES_FAILCNT:
>   		return counter->failcnt;
> +	case HUGETLB_RES_RESERVATION_FAILCNT:
> +		return reserved_counter->failcnt;
>   	default:
>   		BUG();
>   	}
> @@ -291,6 +307,7 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
>   	int ret, idx;
>   	unsigned long nr_pages;
>   	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));
> +	bool reserved = false;
> 
>   	if (hugetlb_cgroup_is_root(h_cg)) /* Can't set limit on root */
>   		return -EINVAL;
> @@ -304,9 +321,13 @@ static ssize_t hugetlb_cgroup_write(struct kernfs_open_file *of,
>   	nr_pages = round_down(nr_pages, 1 << huge_page_order(&hstates[idx]));
> 
>   	switch (MEMFILE_ATTR(of_cft(of)->private)) {
> -	case RES_LIMIT:
> +	case HUGETLB_RES_RESERVATION_LIMIT:
> +		reserved = true;
> +		/* Fall through. */
> +	case HUGETLB_RES_LIMIT:
>   		mutex_lock(&hugetlb_limit_mutex);
> -		ret = page_counter_set_max(&h_cg->hugepage[idx], nr_pages);
> +		ret = page_counter_set_max(hugetlb_cgroup_get_counter(h_cg, idx, reserved),
> +					   nr_pages);
>   		mutex_unlock(&hugetlb_limit_mutex);
>   		break;
>   	default:
> @@ -320,18 +341,26 @@ static ssize_t hugetlb_cgroup_reset(struct kernfs_open_file *of,
>   				    char *buf, size_t nbytes, loff_t off)
>   {
>   	int ret = 0;
> -	struct page_counter *counter;
> +	struct page_counter *counter, *reserved_counter;
>   	struct hugetlb_cgroup *h_cg = hugetlb_cgroup_from_css(of_css(of));
> 
>   	counter = &h_cg->hugepage[MEMFILE_IDX(of_cft(of)->private)];
> +	reserved_counter = &h_cg->reserved_hugepage[
> +		MEMFILE_IDX(of_cft(of)->private)];
> 

Please indent this. It is hard to read.

>   	switch (MEMFILE_ATTR(of_cft(of)->private)) {
> -	case RES_MAX_USAGE:
> +	case HUGETLB_RES_MAX_USAGE:
>   		page_counter_reset_watermark(counter);
>   		break;
> -	case RES_FAILCNT:
> +	case HUGETLB_RES_RESERVATION_MAX_USAGE:
> +		page_counter_reset_watermark(reserved_counter);
> +		break;
> +	case HUGETLB_RES_FAILCNT:
>   		counter->failcnt = 0;
>   		break;
> +	case HUGETLB_RES_RESERVATION_FAILCNT:
> +		reserved_counter->failcnt = 0;
> +		break;
>   	default:
>   		ret = -EINVAL;
>   		break;
> @@ -357,37 +386,67 @@ static void __init __hugetlb_cgroup_file_init(int idx)
>   	struct hstate *h = &hstates[idx];
> 
>   	/* format the size */
> -	mem_fmt(buf, 32, huge_page_size(h));
> +	mem_fmt(buf, sizeof(buf), huge_page_size(h));
> 
>   	/* Add the limit file */
> -	cft = &h->cgroup_files[0];
> +	cft = &h->cgroup_files[HUGETLB_RES_LIMIT];
>   	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.limit_in_bytes", buf);
> -	cft->private = MEMFILE_PRIVATE(idx, RES_LIMIT);
> +	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_LIMIT);
> +	cft->read_u64 = hugetlb_cgroup_read_u64;
> +	cft->write = hugetlb_cgroup_write;
> +
> +	/* Add the reservation limit file */
> +	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_LIMIT];
> +	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_limit_in_bytes",
> +		 buf);
> +	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_LIMIT);
>   	cft->read_u64 = hugetlb_cgroup_read_u64;
>   	cft->write = hugetlb_cgroup_write;
> 
>   	/* Add the usage file */
> -	cft = &h->cgroup_files[1];
> +	cft = &h->cgroup_files[HUGETLB_RES_USAGE];
>   	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.usage_in_bytes", buf);
> -	cft->private = MEMFILE_PRIVATE(idx, RES_USAGE);
> +	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_USAGE);
> +	cft->read_u64 = hugetlb_cgroup_read_u64;
> +
> +	/* Add the reservation usage file */
> +	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_USAGE];
> +	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_usage_in_bytes",
> +			buf);

Please line buf with cft->name for readability.

> +	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_USAGE);
>   	cft->read_u64 = hugetlb_cgroup_read_u64;
> 
>   	/* Add the MAX usage file */
> -	cft = &h->cgroup_files[2];
> +	cft = &h->cgroup_files[HUGETLB_RES_MAX_USAGE];
>   	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.max_usage_in_bytes", buf);
> -	cft->private = MEMFILE_PRIVATE(idx, RES_MAX_USAGE);
> +	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_MAX_USAGE);
> +	cft->write = hugetlb_cgroup_reset;
> +	cft->read_u64 = hugetlb_cgroup_read_u64;
> +
> +	/* Add the MAX reservation usage file */
> +	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_MAX_USAGE];
> +	snprintf(cft->name, MAX_CFTYPE_NAME,
> +			"%s.reservation_max_usage_in_bytes", buf);

Same here.

> +	cft->private = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_MAX_USAGE);
>   	cft->write = hugetlb_cgroup_reset;
>   	cft->read_u64 = hugetlb_cgroup_read_u64;
> 
>   	/* Add the failcntfile */
> -	cft = &h->cgroup_files[3];
> +	cft = &h->cgroup_files[HUGETLB_RES_FAILCNT];
>   	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.failcnt", buf);
> -	cft->private  = MEMFILE_PRIVATE(idx, RES_FAILCNT);
> +	cft->private  = MEMFILE_PRIVATE(idx, HUGETLB_RES_FAILCNT);
> +	cft->write = hugetlb_cgroup_reset;
> +	cft->read_u64 = hugetlb_cgroup_read_u64;
> +
> +	/* Add the reservation failcntfile */
> +	cft = &h->cgroup_files[HUGETLB_RES_RESERVATION_FAILCNT];
> +	snprintf(cft->name, MAX_CFTYPE_NAME, "%s.reservation_failcnt", buf);
> +	cft->private  = MEMFILE_PRIVATE(idx, HUGETLB_RES_RESERVATION_FAILCNT);
>   	cft->write = hugetlb_cgroup_reset;
>   	cft->read_u64 = hugetlb_cgroup_read_u64;
> 
>   	/* NULL terminate the last cft */
> -	cft = &h->cgroup_files[4];
> +	cft = &h->cgroup_files[HUGETLB_RES_NULL];
>   	memset(cft, 0, sizeof(*cft));
> 
>   	WARN_ON(cgroup_add_legacy_cftypes(&hugetlb_cgrp_subsys,
> --
> 2.23.0.162.g0b9fbb3734-goog
> 

thanks,
-- Shuah