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[2003:cb:c74b:3400:ec51:7a3a:274e:cbee]) by smtp.gmail.com with ESMTPSA id z9-20020adff1c9000000b0031f07d1edbcsm12516298wro.77.2023.09.18.04.28.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 Sep 2023 04:28:07 -0700 (PDT) Message-ID: <67c0bbac-aa4a-28ce-5416-e41af794e899@redhat.com> Date: Mon, 18 Sep 2023 13:28:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Subject: Re: [PATCH v1 2/4] mm/ksm: add pages_skipped metric Content-Language: en-US To: Stefan Roesch , kernel-team@fb.com Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, riel@surriel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20230912175228.952039-1-shr@devkernel.io> <20230912175228.952039-3-shr@devkernel.io> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230912175228.952039-3-shr@devkernel.io> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > --- > 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 -- Cheers, David / dhildenb