Steven Rostedt <rostedt@xxxxxxxxxxx> writes:
> On Fri, 10 Feb 2023 13:46:45 -0800
> Stefan Roesch <shr@xxxxxxxxxxxx> wrote:
>
> Sorry for the late reply, I just noticed this (I had the flu when this was
> originally sent).
>
>> +/**
>> + * ksm_remove_ksm_page - called after a ksm page has been removed
>> + *
>> + * @pfn: page frame number of ksm page
>> + *
>> + * Allows to trace the removing of stable ksm pages.
>> + */
>> +TRACE_EVENT(ksm_remove_ksm_page,
>> +
>> + TP_PROTO(unsigned long pfn),
>> +
>> + TP_ARGS(pfn),
>> +
>> + TP_STRUCT__entry(
>> + __field(unsigned long, pfn)
>> + ),
>> +
>> + TP_fast_assign(
>> + __entry->pfn = pfn;
>> + ),
>> +
>> + TP_printk("pfn %lu", __entry->pfn)
>> +);
>> +
>> +/**
>> + * ksm_remove_rmap_item - called after a rmap_item has been removed from the
>> + * stable tree
>> + *
>> + * @pfn: page frame number of ksm page
>> + * @rmap_item: address of rmap_item object
>> + * @mm: address of the process mm struct
>> + *
>> + * Allows to trace the removal of pages from the stable tree list.
>> + */
>> +TRACE_EVENT(ksm_remove_rmap_item,
>> +
>> + TP_PROTO(unsigned long pfn, void *rmap_item, void *mm),
>> +
>> + TP_ARGS(pfn, rmap_item, mm),
>> +
>> + TP_STRUCT__entry(
>> + __field(unsigned long, pfn)
>> + __field(void *, rmap_item)
>> + __field(void *, mm)
>> + ),
>> +
>> + TP_fast_assign(
>> + __entry->pfn = pfn;
>> + __entry->rmap_item = rmap_item;
>> + __entry->mm = mm;
>> + ),
>> +
>> + TP_printk("pfn %lu rmap_item %p mm %p",
>> + __entry->pfn, __entry->rmap_item, __entry->mm)
>> +);
>> +
>> +#endif /* _TRACE_KSM_H */
>> +
>> +/* This part must be outside protection */
>> +#include <trace/define_trace.h>
>> diff --git a/mm/ksm.c b/mm/ksm.c
>> index 56808e3bfd19..4356af760735 100644
>> --- a/mm/ksm.c
>> +++ b/mm/ksm.c
>> @@ -45,6 +45,9 @@
>> #include "internal.h"
>> #include "mm_slot.h"
>>
>> +#define CREATE_TRACE_POINTS
>> +#include <trace/events/ksm.h>
>> +
>> #ifdef CONFIG_NUMA
>> #define NUMA(x) (x)
>> #define DO_NUMA(x) do { (x); } while (0)
>> @@ -655,10 +658,12 @@ static void remove_node_from_stable_tree(struct ksm_stable_node *stable_node)
>> BUG_ON(stable_node->rmap_hlist_len < 0);
>>
>> hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) {
>> - if (rmap_item->hlist.next)
>> + if (rmap_item->hlist.next) {
>> ksm_pages_sharing--;
>> - else
>> + trace_ksm_remove_rmap_item(stable_node->kpfn, rmap_item, rmap_item->mm);
>
> Instead of dereferencing the stable_node here, where the work could
> possibly happen outside the trace event and in the hot path, could you pass
> in the stable_node instead, and then in the TP_fast_assign() do:
>
> __entry->pfn = stable_node->kpfn;
>
>
I'll make the change in the next version.
>> + } else {
>> ksm_pages_shared--;
>> + }
>>
>> rmap_item->mm->ksm_merging_pages--;
>>
>> @@ -679,6 +684,7 @@ static void remove_node_from_stable_tree(struct ksm_stable_node *stable_node)
>> BUILD_BUG_ON(STABLE_NODE_DUP_HEAD <= &migrate_nodes);
>> BUILD_BUG_ON(STABLE_NODE_DUP_HEAD >= &migrate_nodes + 1);
>>
>> + trace_ksm_remove_ksm_page(stable_node->kpfn);
>
> Here too?
>
> -- Steve
>
I'll make the change in the next version.
>> if (stable_node->head == &migrate_nodes)
>> list_del(&stable_node->list);
>> else
>> @@ -1367,6 +1373,8 @@ static int try_to_merge_with_ksm_page(struct ksm_rmap_item *rmap_item,
>> get_anon_vma(vma->anon_vma);
>> out:
>> mmap_read_unlock(mm);
>> + trace_ksm_merge_with_ksm_page(kpage, page_to_pfn(kpage ? kpage : page),
>> + rmap_item, mm, err);
>> return err;
>> }
>>
>> @@ -2114,6 +2122,9 @@ static int try_to_merge_with_kernel_zero_page(struct ksm_rmap_item *rmap_item,
>> if (vma) {
>> err = try_to_merge_one_page(vma, page,
>> ZERO_PAGE(rmap_item->address));
>> + trace_ksm_merge_one_page(
>> + page_to_pfn(ZERO_PAGE(rmap_item->address)),
>> + rmap_item, mm, err);
>> if (!err) {
>> rmap_item->address |= ZERO_PAGE_FLAG;
>> ksm_zero_pages_sharing++;
>> @@ -2344,6 +2355,8 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
>>
>> mm_slot = ksm_scan.mm_slot;
>> if (mm_slot == &ksm_mm_head) {
>> + trace_ksm_start_scan(ksm_scan.seqnr, ksm_rmap_items);
>> +
>> /*
>> * A number of pages can hang around indefinitely on per-cpu
>> * pagevecs, raised page count preventing write_protect_page
>> @@ -2510,6 +2523,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
>> if (mm_slot != &ksm_mm_head)
>> goto next_mm;
>>
>> + trace_ksm_stop_scan(ksm_scan.seqnr, ksm_rmap_items);
>> ksm_scan.seqnr++;
>> return NULL;
>> }
>> @@ -2661,6 +2675,7 @@ int __ksm_enter(struct mm_struct *mm)
>> if (needs_wakeup)
>> wake_up_interruptible(&ksm_thread_wait);
>>
>> + trace_ksm_enter(mm);
>> return 0;
>> }
>>
>> @@ -2702,6 +2717,8 @@ void __ksm_exit(struct mm_struct *mm)
>> mmap_write_lock(mm);
>> mmap_write_unlock(mm);
>> }
>> +
>> + trace_ksm_exit(mm);
>> }
>>
>> struct page *ksm_might_need_to_copy(struct page *page,
>>
>> base-commit: 234a68e24b120b98875a8b6e17a9dead277be16a
