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Date: Thu, 2 Nov 2023 06:34:42 +0000
From: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To: "Huang, Ying" <ying.huang@...el.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"rafael@...nel.org" <rafael@...nel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"Yasunori Gotou (Fujitsu)" <y-goto@...itsu.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 3/4] mm/vmstat: rename pgdemote_* to pgdemote_dst_*
and add pgdemote_src_*
On 02/11/2023 13:45, Huang, Ying wrote:
> Li Zhijian <lizhijian@...itsu.com> writes:
>
>> pgdemote_src_*: pages demoted from this node.
>> pgdemote_dst_*: pages demoted to this node.
>>
>> So that we are able to know their demotion per-node stats by checking this.
>>
>> In the environment, node0 and node1 are DRAM, node3 is PMEM.
>>
>> Global stats:
>> $ grep -E 'demote' /proc/vmstat
>> pgdemote_src_kswapd 130155
>> pgdemote_src_direct 113497
>> pgdemote_src_khugepaged 0
>> pgdemote_dst_kswapd 130155
>> pgdemote_dst_direct 113497
>> pgdemote_dst_khugepaged 0
>>
>> Per-node stats:
>> $ grep demote /sys/devices/system/node/node0/vmstat
>> pgdemote_src_kswapd 68454
>> pgdemote_src_direct 83431
>> pgdemote_src_khugepaged 0
>> pgdemote_dst_kswapd 0
>> pgdemote_dst_direct 0
>> pgdemote_dst_khugepaged 0
>>
>> $ grep demote /sys/devices/system/node/node1/vmstat
>> pgdemote_src_kswapd 185834
>> pgdemote_src_direct 30066
>> pgdemote_src_khugepaged 0
>> pgdemote_dst_kswapd 0
>> pgdemote_dst_direct 0
>> pgdemote_dst_khugepaged 0
>>
>> $ grep demote /sys/devices/system/node/node3/vmstat
>> pgdemote_src_kswapd 0
>> pgdemote_src_direct 0
>> pgdemote_src_khugepaged 0
>> pgdemote_dst_kswapd 254288
>> pgdemote_dst_direct 113497
>> pgdemote_dst_khugepaged 0
>>
>> From above stats, we know node3 is the demotion destination which one
>> the node0 and node1 will demote to.
>
> Why do we need these information? Do you have some use case?
I recall our customers have mentioned that they want to know how much the memory is demoted
to the CXL memory device in a specific period.
>>> mod_node_page_state(NODE_DATA(target_nid),
>>> - PGDEMOTE_KSWAPD + reclaimer_offset(), nr_succeeded);
>>> + PGDEMOTE_DST_KSWAPD + reclaimer_offset(), nr_succeeded);
But if the *target_nid* is only indicate the preferred node, this accounting maybe not accurate.
Thanks
Zhijian
>
> --
> Best Regards,
> Huang, Ying
>
>> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
>> ---
>> RFC: their names are open to discussion, maybe pgdemote_from/to_*
>> Another defect of this patch is that, SUM(pgdemote_src_*) is always same
>> as SUM(pgdemote_dst_*) in the global stats, shall we hide one of them.
>> ---
>> include/linux/mmzone.h | 9 ++++++---
>> mm/vmscan.c | 13 ++++++++++---
>> mm/vmstat.c | 9 ++++++---
>> 3 files changed, 22 insertions(+), 9 deletions(-)
>>
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index ad0309eea850..a6140d894bec 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -207,9 +207,12 @@ enum node_stat_item {
>> PGPROMOTE_SUCCESS, /* promote successfully */
>> PGPROMOTE_CANDIDATE, /* candidate pages to promote */
>> /* PGDEMOTE_*: pages demoted */
>> - PGDEMOTE_KSWAPD,
>> - PGDEMOTE_DIRECT,
>> - PGDEMOTE_KHUGEPAGED,
>> + PGDEMOTE_SRC_KSWAPD,
>> + PGDEMOTE_SRC_DIRECT,
>> + PGDEMOTE_SRC_KHUGEPAGED,
>> + PGDEMOTE_DST_KSWAPD,
>> + PGDEMOTE_DST_DIRECT,
>> + PGDEMOTE_DST_KHUGEPAGED,
>> #endif
>> NR_VM_NODE_STAT_ITEMS
>> };
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 2f1fb4ec3235..55d2287d7150 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1111,13 +1111,18 @@ void drop_slab(void)
>> static int reclaimer_offset(void)
>> {
>> BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
>> - PGDEMOTE_DIRECT - PGDEMOTE_KSWAPD);
>> + PGDEMOTE_SRC_DIRECT - PGDEMOTE_SRC_KSWAPD);
>> BUILD_BUG_ON(PGSTEAL_DIRECT - PGSTEAL_KSWAPD !=
>> PGSCAN_DIRECT - PGSCAN_KSWAPD);
>> BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
>> - PGDEMOTE_KHUGEPAGED - PGDEMOTE_KSWAPD);
>> + PGDEMOTE_SRC_KHUGEPAGED - PGDEMOTE_SRC_KSWAPD);
>> BUILD_BUG_ON(PGSTEAL_KHUGEPAGED - PGSTEAL_KSWAPD !=
>> PGSCAN_KHUGEPAGED - PGSCAN_KSWAPD);
>> + BUILD_BUG_ON(PGDEMOTE_SRC_DIRECT - PGDEMOTE_SRC_KSWAPD !=
>> + PGDEMOTE_DST_DIRECT - PGDEMOTE_DST_KSWAPD);
>> + BUILD_BUG_ON(PGDEMOTE_SRC_KHUGEPAGED - PGDEMOTE_SRC_KSWAPD !=
>> + PGDEMOTE_DST_KHUGEPAGED - PGDEMOTE_DST_KSWAPD);
>> +
>>
>> if (current_is_kswapd())
>> return 0;
>> @@ -1678,8 +1683,10 @@ static unsigned int demote_folio_list(struct list_head *demote_folios,
>> (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION,
>> &nr_succeeded);
>>
>> + mod_node_page_state(pgdat,
>> + PGDEMOTE_SRC_KSWAPD + reclaimer_offset(), nr_succeeded);
>> mod_node_page_state(NODE_DATA(target_nid),
>> - PGDEMOTE_KSWAPD + reclaimer_offset(), nr_succeeded);
>> + PGDEMOTE_DST_KSWAPD + reclaimer_offset(), nr_succeeded);
>>
>> return nr_succeeded;
>> }
>> diff --git a/mm/vmstat.c b/mm/vmstat.c
>> index f141c48c39e4..63f106a5e008 100644
>> --- a/mm/vmstat.c
>> +++ b/mm/vmstat.c
>> @@ -1244,9 +1244,12 @@ const char * const vmstat_text[] = {
>> #ifdef CONFIG_NUMA_BALANCING
>> "pgpromote_success",
>> "pgpromote_candidate",
>> - "pgdemote_kswapd",
>> - "pgdemote_direct",
>> - "pgdemote_khugepaged",
>> + "pgdemote_src_kswapd",
>> + "pgdemote_src_direct",
>> + "pgdemote_src_khugepaged",
>> + "pgdemote_dst_kswapd",
>> + "pgdemote_dst_direct",
>> + "pgdemote_dst_khugepaged",
>> #endif
>>
>> /* enum writeback_stat_item counters */
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