Re: [PATCH 2/3] mm, memcg: inline mem_cgroup_{charge/uncharge} to improve disabled memcg config
From: Johannes Weiner <hidden>
Date: 2021-07-09 14:48:54
Also in:
linux-mm, lkml
On Thu, Jul 08, 2021 at 05:05:08PM -0700, Suren Baghdasaryan wrote:
Inline mem_cgroup_{charge/uncharge} and mem_cgroup_uncharge_list functions
functions to perform mem_cgroup_disabled static key check inline before
calling the main body of the function. This minimizes the memcg overhead
in the pagefault and exit_mmap paths when memcgs are disabled using
cgroup_disable=memory command-line option.
This change results in ~0.4% overhead reduction when running PFT test
comparing {CONFIG_MEMCG=n} against {CONFIG_MEMCG=y, cgroup_disable=memory}
configurationon on an 8-core ARM64 Android device.
Signed-off-by: Suren Baghdasaryan <redacted>Sounds reasonable to me as well. One comment:
quoted hunk ↗ jump to hunk
@@ -693,13 +693,59 @@ static inline bool mem_cgroup_below_min(struct mem_cgroup *memcg) page_counter_read(&memcg->memory); } -int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask); +struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm); + +int __mem_cgroup_charge(struct page *page, struct mem_cgroup *memcg, + gfp_t gfp); +/** + * mem_cgroup_charge - charge a newly allocated page to a cgroup + * @page: page to charge + * @mm: mm context of the victim + * @gfp_mask: reclaim mode + * + * Try to charge @page to the memcg that @mm belongs to, reclaiming + * pages according to @gfp_mask if necessary. if @mm is NULL, try to + * charge to the active memcg. + * + * Do not use this for pages allocated for swapin. + * + * Returns 0 on success. Otherwise, an error code is returned. + */ +static inline int mem_cgroup_charge(struct page *page, struct mm_struct *mm, + gfp_t gfp_mask) +{ + struct mem_cgroup *memcg; + int ret; + + if (mem_cgroup_disabled()) + return 0; + + memcg = get_mem_cgroup_from_mm(mm); + ret = __mem_cgroup_charge(page, memcg, gfp_mask); + css_put(&memcg->css); + + return ret;
Why not do
int __mem_cgroup_charge(struct page *page, struct mm_struct *mm,
gfp_t gfp_mask);
static inline int mem_cgroup_charge(struct page *page, struct mm_struct *mm,
gfp_t gfp_mask)
{
if (mem_cgroup_disabled())
return 0;
return __mem_cgroup_charge(page, memcg, gfp_mask);
}
like in the other cases as well?
That would avoid inlining two separate function calls into all the
callsites...
There is an (internal) __mem_cgroup_charge() already, but you can
rename it charge_memcg().