The patch titled
Subject: /proc/meminfo: add percpu populated pages count
has been added to the -mm tree. Its filename is
proc-add-percpu-populated-pages-count-to-meminfo.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-add-percpu-populated-pages-count-to-meminfo.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-add-percpu-populated-pages-count-to-meminfo.patch
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------------------------------------------------------
From: "Dennis Zhou (Facebook)" <dennisszhou@xxxxxxxxx>
Subject: /proc/meminfo: add percpu populated pages count
Currently, percpu memory only exposes allocation and utilization
information via debugfs. This more or less is only really useful for
understanding the fragmentation and allocation information at a per-chunk
level with a few global counters. This is also gated behind a config.
BPF and cgroup, for example, have seen an increase in use causing
increased use of percpu memory. Let's make it easier for someone to
identify how much memory is being used.
This patch adds the "Percpu" stat to meminfo to more easily look up how
much percpu memory is in use. This number includes the cost for all
allocated backing pages and not just insight at the per a unit, per chunk
level. Metadata is excluded. I think excluding metadata is fair because
the backing memory scales with the numbere of cpus and can quickly
outweigh the metadata. It also makes this calculation light.
Link: http://lkml.kernel.org/r/20180807184723.74919-1-dennisszhou@xxxxxxxxx
Signed-off-by: Dennis Zhou <dennisszhou@xxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/filesystems/proc.txt | 3 ++
fs/proc/meminfo.c | 2 +
include/linux/percpu.h | 2 +
mm/percpu.c | 29 +++++++++++++++++++++++++++
4 files changed, 36 insertions(+)
--- a/Documentation/filesystems/proc.txt~proc-add-percpu-populated-pages-count-to-meminfo
+++ a/Documentation/filesystems/proc.txt
@@ -870,6 +870,7 @@ Committed_AS: 100056 kB
VmallocTotal: 112216 kB
VmallocUsed: 428 kB
VmallocChunk: 111088 kB
+Percpu: 62080 kB
AnonHugePages: 49152 kB
ShmemHugePages: 0 kB
ShmemPmdMapped: 0 kB
@@ -959,6 +960,8 @@ Committed_AS: The amount of memory prese
VmallocTotal: total size of vmalloc memory area
VmallocUsed: amount of vmalloc area which is used
VmallocChunk: largest contiguous block of vmalloc area which is free
+ Percpu: Memory allocated to the percpu allocator used to back percpu
+ allocations. This stat excludes the cost of metadata.
..............................................................................
--- a/fs/proc/meminfo.c~proc-add-percpu-populated-pages-count-to-meminfo
+++ a/fs/proc/meminfo.c
@@ -7,6 +7,7 @@
#include <linux/mman.h>
#include <linux/mmzone.h>
#include <linux/proc_fs.h>
+#include <linux/percpu.h>
#include <linux/quicklist.h>
#include <linux/seq_file.h>
#include <linux/swap.h>
@@ -121,6 +122,7 @@ static int meminfo_proc_show(struct seq_
(unsigned long)VMALLOC_TOTAL >> 10);
show_val_kb(m, "VmallocUsed: ", 0ul);
show_val_kb(m, "VmallocChunk: ", 0ul);
+ show_val_kb(m, "Percpu: ", pcpu_nr_pages());
#ifdef CONFIG_MEMORY_FAILURE
seq_printf(m, "HardwareCorrupted: %5lu kB\n",
--- a/include/linux/percpu.h~proc-add-percpu-populated-pages-count-to-meminfo
+++ a/include/linux/percpu.h
@@ -149,4 +149,6 @@ extern phys_addr_t per_cpu_ptr_to_phys(v
(typeof(type) __percpu *)__alloc_percpu(sizeof(type), \
__alignof__(type))
+extern unsigned long pcpu_nr_pages(void);
+
#endif /* __LINUX_PERCPU_H */
--- a/mm/percpu.c~proc-add-percpu-populated-pages-count-to-meminfo
+++ a/mm/percpu.c
@@ -170,6 +170,14 @@ static LIST_HEAD(pcpu_map_extend_chunks)
int pcpu_nr_empty_pop_pages;
/*
+ * The number of populated pages in use by the allocator, protected by
+ * pcpu_lock. This number is kept per a unit per chunk (i.e. when a page gets
+ * allocated/deallocated, it is allocated/deallocated in all units of a chunk
+ * and increments/decrements this count by 1).
+ */
+static unsigned long pcpu_nr_populated;
+
+/*
* Balance work is used to populate or destroy chunks asynchronously. We
* try to keep the number of populated free pages between
* PCPU_EMPTY_POP_PAGES_LOW and HIGH for atomic allocations and at most one
@@ -1232,6 +1240,7 @@ static void pcpu_chunk_populated(struct
bitmap_set(chunk->populated, page_start, nr);
chunk->nr_populated += nr;
+ pcpu_nr_populated += nr;
if (!for_alloc) {
chunk->nr_empty_pop_pages += nr;
@@ -1260,6 +1269,7 @@ static void pcpu_chunk_depopulated(struc
chunk->nr_populated -= nr;
chunk->nr_empty_pop_pages -= nr;
pcpu_nr_empty_pop_pages -= nr;
+ pcpu_nr_populated -= nr;
}
/*
@@ -2176,6 +2186,9 @@ int __init pcpu_setup_first_chunk(const
pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages;
pcpu_chunk_relocate(pcpu_first_chunk, -1);
+ /* include all regions of the first chunk */
+ pcpu_nr_populated += PFN_DOWN(size_sum);
+
pcpu_stats_chunk_alloc();
trace_percpu_create_chunk(base_addr);
@@ -2746,6 +2759,22 @@ void __init setup_per_cpu_areas(void)
#endif /* CONFIG_SMP */
/*
+ * pcpu_nr_pages - calculate total number of populated backing pages
+ *
+ * This reflects the number of pages populated to back chunks. Metadata is
+ * excluded in the number exposed in meminfo as the number of backing pages
+ * scales with the number of cpus and can quickly outweigh the memory used for
+ * metadata. It also keeps this calculation nice and simple.
+ *
+ * RETURNS:
+ * Total number of populated backing pages in use by the allocator.
+ */
+unsigned long pcpu_nr_pages(void)
+{
+ return pcpu_nr_populated * pcpu_nr_units;
+}
+
+/*
* Percpu allocator is initialized early during boot when neither slab or
* workqueue is available. Plug async management until everything is up
* and running.
_
Patches currently in -mm which might be from dennisszhou@xxxxxxxxx are
proc-add-percpu-populated-pages-count-to-meminfo.patch
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