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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>
This commit is contained in:
Stefan Roesch 2023-02-10 13:46:45 -08:00 committed by Andrew Morton
parent 77f68ebeee
commit 739100c88f
3 changed files with 271 additions and 2 deletions
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MAINTAINERS
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@ -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/

251
include/trace/events/ksm.h Normal file
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@ -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>

21
mm/ksm.c
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@ -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,