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Message-ID: <67c0bbac-aa4a-28ce-5416-e41af794e899@redhat.com>
Date: Mon, 18 Sep 2023 13:28:06 +0200
From: David Hildenbrand <david@...hat.com>
To: Stefan Roesch <shr@...kernel.io>, kernel-team@...com
Cc: akpm@...ux-foundation.org, hannes@...xchg.org, riel@...riel.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v1 2/4] mm/ksm: add pages_skipped metric
On 12.09.23 19:52, Stefan Roesch wrote:
> This change adds the "pages skipped" metric. To be able to evaluate how
> successful smart page scanning is, the pages skipped metric can be
> compared to the pages scanned metric.
>
> The pages skipped metric is a cumulative counter. The counter is stored
> under /sys/kernel/mm/ksm/pages_skipped.
>
> Signed-off-by: Stefan Roesch <shr@...kernel.io>
> ---
> mm/ksm.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/mm/ksm.c b/mm/ksm.c
> index bfd5087c7d5a..728574a3033e 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -293,6 +293,9 @@ static bool ksm_smart_scan;
> /* The number of zero pages which is placed by KSM */
> unsigned long ksm_zero_pages;
>
> +/* The number of pages that have been skipped due to "smart scanning" */
> +static unsigned long ksm_pages_skipped;
> +
> #ifdef CONFIG_NUMA
> /* Zeroed when merging across nodes is not allowed */
> static unsigned int ksm_merge_across_nodes = 1;
> @@ -2345,6 +2348,7 @@ static bool skip_rmap_item(struct page *page, struct ksm_rmap_item *rmap_item)
> return false;
> }
>
> + ksm_pages_skipped++;
> if (rmap_item->skip_age == 0) {
> rmap_item->skip_age = age + inc_skip_age(age);
> remove_rmap_item_from_tree(rmap_item);
> @@ -3435,6 +3439,13 @@ static ssize_t pages_volatile_show(struct kobject *kobj,
> }
> KSM_ATTR_RO(pages_volatile);
>
> +static ssize_t pages_skipped_show(struct kobject *kobj,
> + struct kobj_attribute *attr, char *buf)
> +{
> + return sysfs_emit(buf, "%lu\n", ksm_pages_skipped);
> +}
> +KSM_ATTR_RO(pages_skipped);
> +
> static ssize_t ksm_zero_pages_show(struct kobject *kobj,
> struct kobj_attribute *attr, char *buf)
> {
> @@ -3532,6 +3543,7 @@ static struct attribute *ksm_attrs[] = {
> &pages_sharing_attr.attr,
> &pages_unshared_attr.attr,
> &pages_volatile_attr.attr,
> + &pages_skipped_attr.attr,
> &ksm_zero_pages_attr.attr,
> &full_scans_attr.attr,
> #ifdef CONFIG_NUMA
Reviewed-by: David Hildenbrand <david@...hat.com>
--
Cheers,
David / dhildenb
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