Re: [PATCH] memcg: refactor mem_cgroup_resize_limit()

Nikolay Borisov
2017-06-02T07:32:59Z

On 2.06.2017 02:02, Yu Zhao wrote:
> mem_cgroup_resize_limit() and mem_cgroup_resize_memsw_limit() have
> identical logics. Refactor code so we don't need to keep two pieces
> of code that does same thing.
>
> Signed-off-by: Yu Zhao <yuzhao@google.com>
> ---
> mm/memcontrol.c | 71 +++++++++------------------------------------------------
> 1 file changed, 11 insertions(+), 60 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 94172089f52f..a4f0daaff704 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2422,13 +2422,14 @@ static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
> static DEFINE_MUTEX(memcg_limit_mutex);
>
> static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
> - unsigned long limit)
> + unsigned long limit, bool memsw)
> {
> unsigned long curusage;
> unsigned long oldusage;
> bool enlarge = false;
> int retry_count;
> int ret;
> + struct page_counter *counter = memsw ? &memcg->memsw : &memcg->memory;
>
> /*
> * For keeping hierarchical_reclaim simple, how long we should retry
> @@ -2438,58 +2439,7 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
> retry_count = MEM_CGROUP_RECLAIM_RETRIES *
> mem_cgroup_count_children(memcg);
>
> - oldusage = page_counter_read(&memcg->memory);
> -
> - do {
> - if (signal_pending(current)) {
> - ret = -EINTR;
> - break;
> - }
> -
> - mutex_lock(&memcg_limit_mutex);
> - if (limit > memcg->memsw.limit) {
> - mutex_unlock(&memcg_limit_mutex);
> - ret = -EINVAL;
> - break;
> - }
> - if (limit > memcg->memory.limit)
> - enlarge = true;
> - ret = page_counter_limit(&memcg->memory, limit);
> - mutex_unlock(&memcg_limit_mutex);
> -
> - if (!ret)
> - break;
> -
> - try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, true);
> -
> - curusage = page_counter_read(&memcg->memory);
> - /* Usage is reduced ? */
> - if (curusage >= oldusage)
> - retry_count--;
> - else
> - oldusage = curusage;
> - } while (retry_count);
> -
> - if (!ret && enlarge)
> - memcg_oom_recover(memcg);
> -
> - return ret;
> -}
> -
> -static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
> - unsigned long limit)
> -{
> - unsigned long curusage;
> - unsigned long oldusage;
> - bool enlarge = false;
> - int retry_count;
> - int ret;
> -
> - /* see mem_cgroup_resize_res_limit */
> - retry_count = MEM_CGROUP_RECLAIM_RETRIES *
> - mem_cgroup_count_children(memcg);
> -
> - oldusage = page_counter_read(&memcg->memsw);
> + oldusage = page_counter_read(counter);
>
> do {
> if (signal_pending(current)) {
> @@ -2498,22 +2448,23 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
> }
>
> mutex_lock(&memcg_limit_mutex);
> - if (limit < memcg->memory.limit) {
> + if (memsw ? limit < memcg->memory.limit :
> + limit > memcg->memsw.limit) {

No, just no. Please createa a local variable and use that. Using the
ternary operator in an 'if' statement is just ugly!

> mutex_unlock(&memcg_limit_mutex);
> ret = -EINVAL;
> break;
> }
> - if (limit > memcg->memsw.limit)
> + if (limit > counter->limit)
> enlarge = true;
> - ret = page_counter_limit(&memcg->memsw, limit);
> + ret = page_counter_limit(counter, limit);
> mutex_unlock(&memcg_limit_mutex);
>
> if (!ret)
> break;
>
> - try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, false);
> + try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL, !memsw);
>
> - curusage = page_counter_read(&memcg->memsw);
> + curusage = page_counter_read(counter);
> /* Usage is reduced ? */
> if (curusage >= oldusage)
> retry_count--;
> @@ -2975,10 +2926,10 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
> }
> switch (MEMFILE_TYPE(of_cft(of)->private)) {
> case _MEM:
> - ret = mem_cgroup_resize_limit(memcg, nr_pages);
> + ret = mem_cgroup_resize_limit(memcg, nr_pages, false);
> break;
> case _MEMSWAP:
> - ret = mem_cgroup_resize_memsw_limit(memcg, nr_pages);
> + ret = mem_cgroup_resize_limit(memcg, nr_pages, true);
> break;
> case _KMEM:
> ret = memcg_update_kmem_limit(memcg, nr_pages);
>