[RFC PATCH 41/57] mm/collapse: give collapse its own trace header
From: Kiryl Shutsemau <hidden>
Date: 2026-08-16 22:47:35
Also in:
bpf, linux-kselftest, linux-mm, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), kernel selftest framework, memory management, memory management - misc, memory management - thp (transparent huge page), the rest, tracing · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Shuah Khan, Andrew Morton, David Hildenbrand, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
Every event in include/trace/events/huge_memory.h is a collapse event, and
all but one is emitted from mm/collapse.c. The header is named for
huge_memory.c, which emits none of them, and the tracepoints are built by
khugepaged.c, which emits one.
Rename it to trace/events/collapse.h, with TRACE_SYSTEM to match, and
build the tracepoints in collapse.c.
Two things follow. The pass names a candidate event prints are needed
only where the tracepoints are built, so enum collapse_pass moves out of
mm/collapse.h into collapse.c. And khugepaged.c becomes an ordinary
includer, for the one event it does emit.
The tracefs directory moves with the trace system: events/huge_memory
becomes events/collapse, so anything enabling those events by system name
has to follow.
khugepaged's own selftest does that, and is updated here. So are the two
other in-tree references to the old name: the MAINTAINERS entry for the
header, and the group raw_tp_null_args[] keeps its collapse entries under.
Assisted-by: Claude-Code:claude-opus-5
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
---
MAINTAINERS | 2 +-
.../trace/events/{huge_memory.h => collapse.h} | 8 ++++----
kernel/bpf/btf.c | 6 +++---
mm/collapse.c | 17 ++++++++++++++++-
mm/collapse.h | 13 -------------
mm/khugepaged.c | 3 +--
.../selftests/mm/khugepaged_sync_check.c | 10 +++++-----
tools/testing/selftests/mm/vm_util.c | 2 +-
8 files changed, 31 insertions(+), 30 deletions(-)
rename include/trace/events/{huge_memory.h => collapse.h} (98%)
diff --git a/MAINTAINERS b/MAINTAINERS
index 0f513b42bc18..7c179b333e4e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS@@ -17273,7 +17273,7 @@ F: Documentation/ABI/testing/sysfs-kernel-mm-transparent-hugepage F: Documentation/admin-guide/mm/transhuge.rst F: include/linux/huge_mm.h F: include/linux/khugepaged.h -F: include/trace/events/huge_memory.h +F: include/trace/events/collapse.h F: mm/huge_memory.c F: mm/khugepaged.c F: mm/mm_slot.h
diff --git a/include/trace/events/huge_memory.h b/include/trace/events/collapse.h
similarity index 98%
rename from include/trace/events/huge_memory.h
rename to include/trace/events/collapse.h
index 6aabf4235648..a3af5d8cc9aa 100644
--- a/include/trace/events/huge_memory.h
+++ b/include/trace/events/collapse.h@@ -1,9 +1,9 @@ /* SPDX-License-Identifier: GPL-2.0 */ #undef TRACE_SYSTEM -#define TRACE_SYSTEM huge_memory +#define TRACE_SYSTEM collapse -#if !defined(__HUGE_MEMORY_H) || defined(TRACE_HEADER_MULTI_READ) -#define __HUGE_MEMORY_H +#if !defined(_TRACE_COLLAPSE_H) || defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_COLLAPSE_H #include <linux/tracepoint.h>
@@ -282,5 +282,5 @@ TRACE_EVENT(mm_khugepaged_scan, __entry->full_scan_finished) ); -#endif /* __HUGE_MEMORY_H */ +#endif /* _TRACE_COLLAPSE_H */ #include <trace/define_trace.h>
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 22fc8f974be2..505bdbb534e4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c@@ -6683,6 +6683,9 @@ static const struct bpf_raw_tp_null_args raw_tp_null_args[] = { { "cachefiles_ondemand_cread", 0x1 }, { "cachefiles_ondemand_fd_write", 0x1 }, { "cachefiles_ondemand_fd_release", 0x1 }, + /* collapse */ + { "mm_collapse_scan_file", 0x10 }, + { "mm_collapse_file", 0x10 }, /* ext4, from ext4__mballoc event class */ { "ext4_mballoc_discard", 0x10 }, { "ext4_mballoc_free", 0x10 },
@@ -6702,9 +6705,6 @@ static const struct bpf_raw_tp_null_args raw_tp_null_args[] = { { "time_out_leases", 0x10 }, /* host1x */ { "host1x_cdma_push_gather", 0x10000 }, - /* huge_memory */ - { "mm_collapse_scan_file", 0x10 }, - { "mm_collapse_file", 0x10 }, /* kmem */ { "mm_page_alloc", 0x1 }, { "mm_page_pcpu_drain", 0x1 },
diff --git a/mm/collapse.c b/mm/collapse.c
index 6c17c83a4e21..952e3f62d920 100644
--- a/mm/collapse.c
+++ b/mm/collapse.c@@ -26,10 +26,25 @@ #include <linux/vmstat.h> #include <asm/tlb.h> -#include <trace/events/huge_memory.h> #include "collapse.h" #include "internal.h" +/* + * Which pass of a round reached a verdict on a candidate. Named by the trace + * header, which only this file builds, so it need not be shared. + */ +enum collapse_pass { + COLLAPSE_PASS_ALLOC, + COLLAPSE_PASS_REVALIDATE, + COLLAPSE_PASS_FAULTIN, + COLLAPSE_PASS_FREEZE, + COLLAPSE_PASS_COPY, + COLLAPSE_PASS_INSTALL, +}; + +#define CREATE_TRACE_POINTS +#include <trace/events/collapse.h> + /* * Anonymous collapse, in rounds. *
diff --git a/mm/collapse.h b/mm/collapse.h
index 4af7bb9c4261..9e2cec1f250b 100644
--- a/mm/collapse.h
+++ b/mm/collapse.h@@ -16,19 +16,6 @@ struct collapse_candidate; struct collapse_retry; -/* - * Which pass of a round reached a verdict on a candidate. Only collapse.c - * produces these; the trace header khugepaged.c builds names them. - */ -enum collapse_pass { - COLLAPSE_PASS_ALLOC, - COLLAPSE_PASS_REVALIDATE, - COLLAPSE_PASS_FAULTIN, - COLLAPSE_PASS_FREEZE, - COLLAPSE_PASS_COPY, - COLLAPSE_PASS_INSTALL, -}; - enum scan_result { SCAN_FAIL, SCAN_SUCCEED,
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 967cc472b6dc..f3a7aad5e8f2 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c@@ -31,8 +31,7 @@ #include "page_alloc.h" #include "mm_slot.h" -#define CREATE_TRACE_POINTS -#include <trace/events/huge_memory.h> +#include <trace/events/collapse.h> static struct task_struct *khugepaged_thread __read_mostly; static DEFINE_MUTEX(khugepaged_mutex);
diff --git a/tools/testing/selftests/mm/khugepaged_sync_check.c b/tools/testing/selftests/mm/khugepaged_sync_check.c
index 45001996b57a..4c37b697d3dd 100644
--- a/tools/testing/selftests/mm/khugepaged_sync_check.c
+++ b/tools/testing/selftests/mm/khugepaged_sync_check.c@@ -41,7 +41,7 @@ static unsigned long hpage_pmd_size; /* * Each step switches the events off again, but a helper can still give up * on us in between (a failing sysfs write ends the test from inside - * thp_write_num()), and huge_memory events left on are the whole machine's + * thp_write_num()), and collapse events left on are the whole machine's * problem, not this test's. */ static void trace_events_off(void)
@@ -118,7 +118,7 @@ static void one_step(int iteration) if (tracing_clear_trace()) ksft_exit_fail_msg("Cannot clear the trace buffer\n"); if (tracing_events_enable(trace_events_fd, true)) - ksft_exit_fail_msg("Cannot enable huge_memory events\n"); + ksft_exit_fail_msg("Cannot enable collapse events\n"); if (madvise(p, hpage_pmd_size, MADV_HUGEPAGE)) ksft_exit_fail_perror("madvise(MADV_HUGEPAGE)");
@@ -127,7 +127,7 @@ static void one_step(int iteration) /* Off before anything that can give up: the events are system-wide. */ if (tracing_events_enable(trace_events_fd, false)) - ksft_exit_fail_msg("Cannot disable huge_memory events\n"); + ksft_exit_fail_msg("Cannot disable collapse events\n"); if (!passed) ksft_exit_fail_msg("khugepaged did not complete a full pass\n");
@@ -164,9 +164,9 @@ int main(void) kpageflags_fd = open("/proc/kpageflags", O_RDONLY); if (kpageflags_fd < 0) ksft_exit_skip("open(\"/proc/kpageflags\") requires root\n"); - trace_events_fd = tracing_events_open("huge_memory"); + trace_events_fd = tracing_events_open("collapse"); if (trace_events_fd < 0) - ksft_exit_skip("huge_memory events require tracefs and root\n"); + ksft_exit_skip("collapse events require tracefs and root\n"); atexit(trace_events_off); ksft_set_plan(NR_ITERATIONS);
diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
index ee1334778391..32cba59ae49c 100644
--- a/tools/testing/selftests/mm/vm_util.c
+++ b/tools/testing/selftests/mm/vm_util.c@@ -601,7 +601,7 @@ bool is_range_backed_by_folio_orders(char *start, size_t len, int order, #define TRACEFS_ROOT "/sys/kernel/tracing" /* - * Open the enable file of one ftrace event subsystem (e.g. "huge_memory"). + * Open the enable file of one ftrace event subsystem (e.g. "collapse"). * Returns a descriptor for tracing_events_enable(), or -1 if tracefs or the * subsystem is not there. The events are system-wide state: whoever * switches them on owns them until it switches them off, including on the
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2.54.0