mm: add tracepoints to ksm

This adds the following tracepoints to ksm:
- start / stop scan
- ksm enter / exit
- merge a page
- merge a page with ksm
- remove a page
- remove a rmap item

This patch has been split off from the RFC patch series "mm:
process/cgroup ksm support".

Link: https://lkml.kernel.org/r/20230210214645.2720847-1-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/MAINTAINERS b/MAINTAINERS
index 1dc8bd2..a62ffb7 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13409,6 +13409,7 @@ F:      include/linux/memory_hotplug.h
 F:     include/linux/mm.h
 F:     include/linux/mmzone.h
 F:     include/linux/pagewalk.h
+F:     include/trace/events/ksm.h
 F:     mm/
 F:     tools/mm/
 F:     tools/testing/selftests/mm/

diff --git a/include/trace/events/ksm.h b/include/trace/events/ksm.h
new file mode 100644 (file)
index 0000000..b5ac35c
--- /dev/null
+++ b/include/trace/events/ksm.h
@@ -0,0 +1,251 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM ksm
+
+#if !defined(_TRACE_KSM_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_KSM_H
+
+#include <linux/tracepoint.h>
+
+/**
+ * ksm_scan_template - called for start / stop scan
+ *
+ * @seq:               sequence number of scan
+ * @rmap_entries:      actual number of rmap entries
+ *
+ * Allows to trace the start / stop of a ksm scan.
+ */
+DECLARE_EVENT_CLASS(ksm_scan_template,
+
+       TP_PROTO(int seq, u32 rmap_entries),
+
+       TP_ARGS(seq, rmap_entries),
+
+       TP_STRUCT__entry(
+               __field(int,    seq)
+               __field(u32,    rmap_entries)
+       ),
+
+       TP_fast_assign(
+               __entry->seq            = seq;
+               __entry->rmap_entries   = rmap_entries;
+       ),
+
+       TP_printk("seq %d rmap size %d",
+                       __entry->seq, __entry->rmap_entries)
+);
+
+/**
+ * ksm_start_scan - called after a new ksm scan is started
+ *
+ * @seq:               sequence number of scan
+ * @rmap_entries:      actual number of rmap entries
+ *
+ * Allows to trace the start of a ksm scan.
+ */
+DEFINE_EVENT(ksm_scan_template, ksm_start_scan,
+
+       TP_PROTO(int seq, u32 rmap_entries),
+
+       TP_ARGS(seq, rmap_entries)
+);
+
+/**
+ * ksm_stop_scan - called after a new ksm scan has completed
+ *
+ * @seq:               sequence number of scan
+ * @rmap_entries:      actual number of rmap entries
+ *
+ * Allows to trace the completion of a ksm scan.
+ */
+DEFINE_EVENT(ksm_scan_template, ksm_stop_scan,
+
+       TP_PROTO(int seq, u32 rmap_entries),
+
+       TP_ARGS(seq, rmap_entries)
+);
+
+/**
+ * ksm_enter - called after a new process has been added / removed from ksm
+ *
+ * @mm:                        address of the mm object of the process
+ *
+ * Allows to trace the when a process has been added or removed from ksm.
+ */
+DECLARE_EVENT_CLASS(ksm_enter_exit_template,
+
+       TP_PROTO(void *mm),
+
+       TP_ARGS(mm),
+
+       TP_STRUCT__entry(
+               __field(void *,         mm)
+       ),
+
+       TP_fast_assign(
+               __entry->mm     = mm;
+       ),
+
+       TP_printk("mm %p", __entry->mm)
+);
+
+/**
+ * ksm_enter - called after a new process has been added to ksm
+ *
+ * @mm:                        address of the mm object of the process
+ *
+ * Allows to trace the when a process has been added to ksm.
+ */
+DEFINE_EVENT(ksm_enter_exit_template, ksm_enter,
+
+       TP_PROTO(void *mm),
+
+       TP_ARGS(mm)
+);
+
+/**
+ * ksm_exit - called after a new process has been removed from ksm
+ *
+ * @mm:                        address of the mm object of the process
+ *
+ * Allows to trace the when a process has been removed from ksm.
+ */
+DEFINE_EVENT(ksm_enter_exit_template, ksm_exit,
+
+       TP_PROTO(void *mm),
+
+       TP_ARGS(mm)
+);
+
+/**
+ * ksm_merge_one_page - called after a page has been merged
+ *
+ * @pfn:               page frame number of ksm page
+ * @rmap_item:         address of rmap_item  object
+ * @mm:                        address of the process mm struct
+ * @err:               success
+ *
+ * Allows to trace the ksm merging of individual pages.
+ */
+TRACE_EVENT(ksm_merge_one_page,
+
+       TP_PROTO(unsigned long pfn, void *rmap_item, void *mm, int err),
+
+       TP_ARGS(pfn, rmap_item, mm, err),
+
+       TP_STRUCT__entry(
+               __field(unsigned long,  pfn)
+               __field(void *,         rmap_item)
+               __field(void *,         mm)
+               __field(int,            err)
+       ),
+
+       TP_fast_assign(
+               __entry->pfn            = pfn;
+               __entry->rmap_item      = rmap_item;
+               __entry->mm             = mm;
+               __entry->err            = err;
+       ),
+
+       TP_printk("ksm pfn %lu rmap_item %p mm %p error %d",
+                       __entry->pfn, __entry->rmap_item, __entry->mm, __entry->err)
+);
+
+/**
+ * ksm_merge_with_ksm_page - called after a page has been merged with a ksm page
+ *
+ * @ksm_page:          address ksm page
+ * @pfn:               page frame number of ksm page
+ * @rmap_item:         address of rmap_item  object
+ * @mm:                        address of the mm object of the process
+ * @err:               success
+ *
+ * Allows to trace the merging of a page with a ksm page.
+ */
+TRACE_EVENT(ksm_merge_with_ksm_page,
+
+       TP_PROTO(void *ksm_page, unsigned long pfn, void *rmap_item, void *mm, int err),
+
+       TP_ARGS(ksm_page, pfn, rmap_item, mm, err),
+
+       TP_STRUCT__entry(
+               __field(void *,         ksm_page)
+               __field(unsigned long,  pfn)
+               __field(void *,         rmap_item)
+               __field(void *,         mm)
+               __field(int,            err)
+       ),
+
+       TP_fast_assign(
+               __entry->ksm_page       = ksm_page;
+               __entry->pfn            = pfn;
+               __entry->rmap_item      = rmap_item;
+               __entry->mm             = mm;
+               __entry->err            = err;
+       ),
+
+       TP_printk("%spfn %lu rmap_item %p mm %p error %d",
+                 (__entry->ksm_page ? "ksm " : ""),
+                 __entry->pfn, __entry->rmap_item, __entry->mm, __entry->err)
+);
+
+/**
+ * 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 2b8d300..290a3eb 100644 (file)
--- 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)
@@ -633,10 +636,12 @@ 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);
+               } else {
                        ksm_pages_shared--;
+               }
 
                rmap_item->mm->ksm_merging_pages--;
 
@@ -657,6 +662,7 @@ 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);
        if (stable_node->head == &migrate_nodes)
                list_del(&stable_node->list);
        else
@@ -1324,6 +1330,8 @@ 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;
 }
 
@@ -2142,6 +2150,9 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
                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);
                } else {
                        /*
                         * If the vma is out of date, we do not need to
@@ -2264,6 +2275,8 @@ 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
@@ -2414,6 +2427,7 @@ no_vmas:
        if (mm_slot != &ksm_mm_head)
                goto next_mm;
 
+       trace_ksm_stop_scan(ksm_scan.seqnr, ksm_rmap_items);
        ksm_scan.seqnr++;
        return NULL;
 }
@@ -2565,6 +2579,7 @@ int __ksm_enter(struct mm_struct *mm)
        if (needs_wakeup)
                wake_up_interruptible(&ksm_thread_wait);
 
+       trace_ksm_enter(mm);
        return 0;
 }
 
@@ -2606,6 +2621,8 @@ 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,