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BACKPORT: FROMGIT: mm/page_alloc: add trace event for per-zone watermark setup

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Patch series "Add tracepoints for lowmem reserves, watermarks and
totalreserve_pages", v2.

This patchset introduces tracepoints to track changes in the lowmem
reserves, watermarks and totalreserve_pages. This helps to track
the exact timing of such changes and understand their relation to
reclaim activities.

The tracepoints added are:

mm_setup_per_zone_lowmem_reserve
mm_setup_per_zone_wmarks
mm_calculate_totalreserve_pagesi

This patch (of 3):

This commit introduces the `mm_setup_per_zone_wmarks` trace event,
which provides detailed insights into the kernel's per-zone watermark
configuration, offering precise timing and the ability to correlate
watermark changes with specific kernel events.

While `/proc/zoneinfo` provides some information about zone watermarks,
this trace event offers:

1. The ability to link watermark changes to specific kernel events and
   logic.

2. The ability to capture rapid or short-lived changes in watermarks
   that may be missed by user-space polling

3. Diagnosing unexpected kswapd activity or excessive direct reclaim
   triggered by rapidly changing watermarks.

Link: https://lkml.kernel.org/r/20250308034606.2036033-1-liumartin@google.com
Link: https://lkml.kernel.org/r/20250308034606.2036033-2-liumartin@google.com
Signed-off-by: Martin Liu <liumartin@google.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Martin Liu <liumartin@google.com>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Bug: 396115949
(cherry picked from commit 8c02048d1c6126527f15752a5e0849dc49cefeeb
 https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable)
Change-Id: I7e326e78542abb6fa5f3ccbe5d61a59f42d7cf2f
Signed-off-by: Martin Liu <liumartin@google.com>
This commit is contained in:
Martin Liu
2025-03-08 03:46:00 +00:00
parent 7da329f7cf
commit 9d6305174c
2 changed files with 34 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
include/trace/events/kmem.h
View File

@@ -342,6 +342,39 @@ TRACE_EVENT(mm_alloc_contig_migrate_range_info,
__entry->nr_mapped)
);
TRACE_EVENT(mm_setup_per_zone_wmarks,
TP_PROTO(struct zone *zone),
TP_ARGS(zone),
TP_STRUCT__entry(
__field(int, node_id)
__string(name, zone->name)
__field(unsigned long, watermark_min)
__field(unsigned long, watermark_low)
__field(unsigned long, watermark_high)
__field(unsigned long, watermark_promo)
),
TP_fast_assign(
__entry->node_id = zone->zone_pgdat->node_id;
__assign_str(name, zone->name);
__entry->watermark_min = zone->_watermark[WMARK_MIN];
__entry->watermark_low = zone->_watermark[WMARK_LOW];
__entry->watermark_high = zone->_watermark[WMARK_HIGH];
__entry->watermark_promo = zone->_watermark[WMARK_PROMO];
),
TP_printk("node_id=%d zone name=%s watermark min=%lu low=%lu high=%lu promo=%lu",
__entry->node_id,
__get_str(name),
__entry->watermark_min,
__entry->watermark_low,
__entry->watermark_high,
__entry->watermark_promo)
);
/*
* Required for uniquely and securely identifying mm in rss_stat tracepoint.
*/

1
mm/page_alloc.c
View File

@@ -9070,6 +9070,7 @@ static void __setup_per_zone_wmarks(void)
zone->_watermark[WMARK_LOW] = min_wmark_pages(zone) + tmp;
zone->_watermark[WMARK_HIGH] = low_wmark_pages(zone) + tmp;
zone->_watermark[WMARK_PROMO] = high_wmark_pages(zone) + tmp;
trace_mm_setup_per_zone_wmarks(zone);
spin_unlock_irqrestore(&zone->lock, flags);
}