[Devel] [PATCH vz8.4 1/4] ve/memcg: Fix /proc/meminfo virtualization (eliminate double recursion)

[Kirill Tkhai]

On 22.07.2021 17:23, Konstantin Khorenko wrote:
> This patch partially reverts commit 47f1b6c1d8e5 ("ve/memcg: Make
> virtualization of /proc/meminfo view inside CT recursive")
> 
> In vz8 we have both memcg->vmstats (recursive) and
> memcg->vmstats_local (non-recursive), and mem_page_state_recursive()
> brought by the reverted commit does double recursion,
> so revert that logic, but leave the other stuff.
> 
> Fixes: 47f1b6c1d8e5 ("ve/memcg: Make virtualization of /proc/meminfo
> view inside CT recursive")
> 
> To_merge: 38a2f168a441 ("ve/proc: virtualize /proc/meminfo in a Container")
> 
> https://jira.sw.ru/browse/PSBM-131992
> 
> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>

Reviewed-by: Kirill Tkhai <ktkhai at virtuozzo.com>

> ---
>  mm/memcontrol.c | 26 +++++++-------------------
>  1 file changed, 7 insertions(+), 19 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index d3aa1cf20796..c1e23f0bbe91 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4151,29 +4151,17 @@ void mem_cgroup_get_nr_pages(struct mem_cgroup *memcg, unsigned long *pages)
>  		pages[lru] += mem_cgroup_nr_lru_pages(memcg, BIT(lru), true);
>  }
>  
> -static unsigned long mem_page_state_recursive(struct mem_cgroup *memcg,
> -					      int idx)
> -{
> -	struct mem_cgroup *iter;
> -	unsigned long val = 0;
> -
> -	for_each_mem_cgroup_tree(iter, memcg)
> -		val += memcg_page_state(iter, idx);
> -
> -	return val;
> -}
> -
>  void mem_cgroup_fill_meminfo(struct mem_cgroup *memcg, struct meminfo *mi)
>  {
>  	memset(&mi->pages, 0, sizeof(mi->pages));
>  	mem_cgroup_get_nr_pages(memcg, mi->pages);
>  
> -	mi->slab_reclaimable = mem_page_state_recursive(memcg, NR_SLAB_RECLAIMABLE_B);
> -	mi->slab_unreclaimable = mem_page_state_recursive(memcg, NR_SLAB_UNRECLAIMABLE_B);
> -	mi->cached = mem_page_state_recursive(memcg, NR_FILE_PAGES);
> -	mi->shmem = mem_page_state_recursive(memcg, NR_SHMEM);
> -	mi->dirty_pages = mem_page_state_recursive(memcg, NR_FILE_DIRTY);
> -	mi->writeback_pages = mem_page_state_recursive(memcg, NR_WRITEBACK);
> +	mi->slab_reclaimable	= memcg_page_state(memcg, NR_SLAB_RECLAIMABLE_B);
> +	mi->slab_unreclaimable	= memcg_page_state(memcg, NR_SLAB_UNRECLAIMABLE_B);
> +	mi->cached		= memcg_page_state(memcg, NR_FILE_PAGES);
> +	mi->shmem		= memcg_page_state(memcg, NR_SHMEM);
> +	mi->dirty_pages		= memcg_page_state(memcg, NR_FILE_DIRTY);
> +	mi->writeback_pages	= memcg_page_state(memcg, NR_WRITEBACK);

My subjective IMHO is that that this is worse for grepping "writeback_pages = " pattern.
But this is not a rule have, since we have both variants in kernel.

>  
>  	/* locked pages are accounted per zone */
>  	/* mi->locked = 0; */
> @@ -4184,7 +4172,7 @@ void mem_cgroup_fill_meminfo(struct mem_cgroup *memcg, struct meminfo *mi)
>  	 * are not taken into account. These values reflect reservation of
>  	 * physycal memory and they are not relevant for CT.
>  	 */
> -	mi->available = mi->si->freeram;
> +	mi->available  = mi->si->freeram;
>  	mi->available += mi->pages[LRU_ACTIVE_FILE] +
>  			 mi->pages[LRU_INACTIVE_FILE];
>  	mi->available += mi->slab_reclaimable;
>