[Devel] [PATCH RH8] kstat: Make kstat_glob::swap_in percpu

[Kirill Tkhai]

On 19.04.2021 11:19, Andrey Zhadchenko wrote:
> From: Kirill Tkhai <ktkhai at virtuozzo.com>
> 
> Patchset description:
> Make kstat_glob::swap_in percpu and cleanup
> 
> This patchset continues escaping of kstat_glb_lock
> and makes swap_in percpu. Also, newly unused primitives
> are dropped and reduced memory usage by using percpu
> seqcount (instead of separate percpu seqcount for every
> kstat percpu variable).
> 
> Kirill Tkhai (4):
>       kstat: Make kstat_glob::swap_in percpu
>       kstat: Drop global kstat_lat_struct
>       kstat: Drop cpu argument in KSTAT_LAT_PCPU_ADD()
>       kstat: Make global percpu kstat_pcpu_seq instead of percpu seq for every
>              variable
> 
> ==========================================
> This patch description:
> 
> Using of global local is not good for scalability.
> Better we make swap_in percpu, and it will be updated
> lockless like other statistics (e.g., page_in).
> 
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> 
> Ported to vz8:
>  - Dropped all patchset but this patch, since it is already partially included
>  - Introduced start in do_swap_page to use it for kstat_glob.swap_in
> 
> (cherry picked from ed033a381e01996f7f8061d9838d1c9ec6b38d96)
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>

Looks OK for me.

> ---
>  mm/memory.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index b64f317..3a48379 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3037,7 +3037,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>  	int locked;
>  	int exclusive = 0;
>  	vm_fault_t ret = 0;
> +	cycles_t start;
>  
> +	start = get_cycles();
>  	if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
>  		goto out;
>  
> @@ -3226,6 +3228,10 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>  unlock:
>  	pte_unmap_unlock(vmf->pte, vmf->ptl);
>  out:
> +	local_irq_disable();
> +	KSTAT_LAT_PCPU_ADD(&kstat_glob.swap_in, get_cycles() - start);
> +	local_irq_enable();
> +
>  	return ret;
>  out_nomap:
>  	mem_cgroup_cancel_charge(page, memcg, false);
>