Re: [PATCH 1/2] mm: add per-order mTHP split counters

Bang Li <libang.linux@xxxxxxxxx> · Thu, 25 Apr 2024 01:58:53 +0800

Hey, sorry for making noise, there was something wrong with the format of
the last email.

On 2024/4/25 1:12, Bang Li wrote:
Hey Lance,

On 2024/4/24 21:51, Lance Yang wrote:

At present, the split counters in THP statistics no longer include
PTE-mapped mTHP. Therefore, this commit introduces per-order mTHP split
counters to monitor the frequency of mTHP splits. This will assist
developers in better analyzing and optimizing system performance.

/sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats
         split_page
         split_page_failed
         deferred_split_page

Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>
---
  include/linux/huge_mm.h |  3 +++
  mm/huge_memory.c        | 14 ++++++++++++--
  2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 56c7ea73090b..7b9c6590e1f7 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -272,6 +272,9 @@ enum mthp_stat_item {
      MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
      MTHP_STAT_ANON_SWPOUT,
      MTHP_STAT_ANON_SWPOUT_FALLBACK,
+    MTHP_STAT_SPLIT_PAGE,
+    MTHP_STAT_SPLIT_PAGE_FAILED,
+    MTHP_STAT_DEFERRED_SPLIT_PAGE,
      __MTHP_STAT_COUNT
  };
  diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 055df5aac7c3..52db888e47a6 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -557,6 +557,9 @@ DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, 
MTHP_STAT_ANON_FAULT_FALLBACK);
  DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, 
MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
  DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
  DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, 
MTHP_STAT_ANON_SWPOUT_FALLBACK);
+DEFINE_MTHP_STAT_ATTR(split_page, MTHP_STAT_SPLIT_PAGE);
+DEFINE_MTHP_STAT_ATTR(split_page_failed, MTHP_STAT_SPLIT_PAGE_FAILED);
+DEFINE_MTHP_STAT_ATTR(deferred_split_page, 
MTHP_STAT_DEFERRED_SPLIT_PAGE);
    static struct attribute *stats_attrs[] = {
      &anon_fault_alloc_attr.attr,
@@ -564,6 +567,9 @@ static struct attribute *stats_attrs[] = {
      &anon_fault_fallback_charge_attr.attr,
      &anon_swpout_attr.attr,
      &anon_swpout_fallback_attr.attr,
+    &split_page_attr.attr,
+    &split_page_failed_attr.attr,
+    &deferred_split_page_attr.attr,
      NULL,
  };
  @@ -3083,7 +3089,7 @@ int split_huge_page_to_list_to_order(struct 
page *page, struct list_head *list,
      XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, 
new_order);
      struct anon_vma *anon_vma = NULL;
      struct address_space *mapping = NULL;
-    bool is_thp = folio_test_pmd_mappable(folio);
+    int order = folio_order(folio);
      int extra_pins, ret;
      pgoff_t end;
      bool is_hzp;
@@ -3262,8 +3268,10 @@ int split_huge_page_to_list_to_order(struct 
page *page, struct list_head *list,
          i_mmap_unlock_read(mapping);
  out:
      xas_destroy(&xas);
-    if (is_thp)
+    if (order >= HPAGE_PMD_ORDER)
          count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
+    count_mthp_stat(order, !ret ? MTHP_STAT_SPLIT_PAGE :
+                      MTHP_STAT_SPLIT_PAGE_FAILED);
      return ret;
  }
  @@ -3327,6 +3335,8 @@ void deferred_split_folio(struct folio *folio)
      if (list_empty(&folio->_deferred_list)) {
          if (folio_test_pmd_mappable(folio))
              count_vm_event(THP_DEFERRED_SPLIT_PAGE);
+        count_mthp_stat(folio_order(folio),
+                MTHP_STAT_DEFERRED_SPLIT_PAGE);
          list_add_tail(&folio->_deferred_list, &ds_queue->split_queue);
          ds_queue->split_queue_len++;
  #ifdef CONFIG_MEMCG

My opinion can be ignored :). Would it be better to modify the 
deferred_split_folio
function as follows? I'm not sure.

diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 
055df5aac7c3..e8562e8630b1 100644 --- a/mm/huge_memory.c +++ 
b/mm/huge_memory.c @@ -3299,12 +3299,13 @@ void 
deferred_split_folio(struct folio *folio) struct mem_cgroup *memcg = 
folio_memcg(folio); #endif unsigned long flags; + int order = 
folio_order(folio); /* * Order 1 folios have no space for a deferred 
list, but we also * won't waste much memory by not adding them to the 
deferred list. */ - if (folio_order(folio) <= 1) + if (order <= 1) 
return; /* @@ -3325,8 +3326,9 @@ void deferred_split_folio(struct 
folio *folio) spin_lock_irqsave(&ds_queue->split_queue_lock, flags); 
if (list_empty(&folio->_deferred_list)) { - if 
(folio_test_pmd_mappable(folio)) + if (order >= HPAGE_PMD_ORDER) 
count_vm_event(THP_DEFERRED_SPLIT_PAGE); + count_mthp_stat(order, 
MTHP_STAT_DEFERRED_SPLIT_PAGE); list_add_tail(&folio->_deferred_list, 
&ds_queue->split_queue); ds_queue->split_queue_len++; #ifdef 
CONFIG_MEMCG thanks,
bang


My opinion can be ignored :). Would it be better to modify the 
deferred_split_folio
function as follows? I'm not sure.

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 055df5aac7c3..e8562e8630b1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3299,12 +3299,13 @@ void deferred_split_folio(struct folio *folio)
        struct mem_cgroup *memcg = folio_memcg(folio);
 #endif
        unsigned long flags;
+       int order = folio_order(folio);

        /*
         * Order 1 folios have no space for a deferred list, but we also
         * won't waste much memory by not adding them to the deferred list.
         */
-       if (folio_order(folio) <= 1)
+       if (order <= 1)
                return;

        /*
@@ -3325,8 +3326,9 @@ void deferred_split_folio(struct folio *folio)

        spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
        if (list_empty(&folio->_deferred_list)) {
-               if (folio_test_pmd_mappable(folio))
+               if (order >= HPAGE_PMD_ORDER)
                        count_vm_event(THP_DEFERRED_SPLIT_PAGE);
+               count_mthp_stat(order, MTHP_STAT_DEFERRED_SPLIT_PAGE);
                list_add_tail(&folio->_deferred_list, 
&ds_queue->split_queue);
                ds_queue->split_queue_len++;
 #ifdef CONFIG_MEMCG

thanks,
bang







