[PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

Currently we display some hugepage statistics (total, free, etc)
in /proc/meminfo, but only for default hugepage size (e.g. 2Mb).

If hugepages of different sizes are used (like 2Mb and 1Gb on x86-64),
/proc/meminfo output can be confusing, as non-default sized hugepages
are not reflected at all, and there are no signs that they are
existing and consuming system memory.

To solve this problem, let's display stats for all hugepage sizes.
To provide the backward compatibility let's save the existing format
for the default size, and add a prefix (e.g. 1G_) for non-default sizes.

For example (100 2Mb pages and 2 1Gb pages are pre-allocated):
  $ cat /proc/meminfo
  MemTotal:        8168976 kB
  MemFree:         5664792 kB
  <...>
  CmaFree:               0 kB
  HugePages_1G_Total:       2
  HugePages_1G_Free:        2
  HugePages_1G_Rsvd:        0
  HugePages_1G_Surp:        0
  Hugepagesize_1G:    1048576 kB
  HugePages_Total:     100
  HugePages_Free:      100
  HugePages_Rsvd:        0
  HugePages_Surp:        0
  Hugepagesize:       2048 kB
  DirectMap4k:       30584 kB
  DirectMap2M:     3115008 kB
  DirectMap1G:     7340032 kB

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: kernel-team@fb.com
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/hugetlb.c | 49 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 12 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4b3bbd2980bb..abd37999f5da 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2973,20 +2973,45 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
 
 void hugetlb_report_meminfo(struct seq_file *m)
 {
-	struct hstate *h = &default_hstate;
+	struct hstate *h;
+
 	if (!hugepages_supported())
 		return;
-	seq_printf(m,
-			"HugePages_Total:   %5lu\n"
-			"HugePages_Free:    %5lu\n"
-			"HugePages_Rsvd:    %5lu\n"
-			"HugePages_Surp:    %5lu\n"
-			"Hugepagesize:   %8lu kB\n",
-			h->nr_huge_pages,
-			h->free_huge_pages,
-			h->resv_huge_pages,
-			h->surplus_huge_pages,
-			1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
+
+	for_each_hstate(h) {
+		char prefix[16] = "";
+
+		if (h != &default_hstate) {
+			unsigned int order = huge_page_order(h) + PAGE_SHIFT;
+			char suffix = '_';
+
+			if (order >= 30) {
+				order -= 30;
+				suffix = 'G';
+			} else if (order >= 20) {
+				order -= 20;
+				suffix = 'M';
+			} else if (order >= 10) {
+				order -= 10;
+				suffix = 'k';
+			}
+
+			snprintf(prefix, sizeof(prefix), "_%lu%c",
+				 1UL << order, suffix);
+		}
+
+		seq_printf(m,
+			"HugePages%s_Total:   %5lu\n"
+			"HugePages%s_Free:    %5lu\n"
+			"HugePages%s_Rsvd:    %5lu\n"
+			"HugePages%s_Surp:    %5lu\n"
+			"Hugepagesize%s:   %8lu kB\n",
+			prefix, h->nr_huge_pages,
+			prefix, h->free_huge_pages,
+			prefix, h->resv_huge_pages,
+			prefix, h->surplus_huge_pages,
+			prefix, 1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
+	}
 }
 
 int hugetlb_report_node_meminfo(int nid, char *buf)
-- 
2.13.6

[PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

Currently we display some hugepage statistics (total, free, etc)
in /proc/meminfo, but only for default hugepage size (e.g. 2Mb).

If hugepages of different sizes are used (like 2Mb and 1Gb on x86-64),
/proc/meminfo output can be confusing, as non-default sized hugepages
are not reflected at all, and there are no signs that they are
existing and consuming system memory.

To solve this problem, let's display stats for all hugepage sizes.
To provide the backward compatibility let's save the existing format
for the default size, and add a prefix (e.g. 1G_) for non-default sizes.

For example (100 2Mb pages and 2 1Gb pages are pre-allocated):
  $ cat /proc/meminfo
  MemTotal:        8168976 kB
  MemFree:         5664792 kB
  <...>
  CmaFree:               0 kB
  HugePages_1G_Total:       2
  HugePages_1G_Free:        2
  HugePages_1G_Rsvd:        0
  HugePages_1G_Surp:        0
  Hugepagesize_1G:    1048576 kB
  HugePages_Total:     100
  HugePages_Free:      100
  HugePages_Rsvd:        0
  HugePages_Surp:        0
  Hugepagesize:       2048 kB
  DirectMap4k:       30584 kB
  DirectMap2M:     3115008 kB
  DirectMap1G:     7340032 kB

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: kernel-team@fb.com
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
---
 mm/hugetlb.c | 49 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 12 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4b3bbd2980bb..abd37999f5da 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2973,20 +2973,45 @@ int hugetlb_overcommit_handler(struct ctl_table *table, int write,
 
 void hugetlb_report_meminfo(struct seq_file *m)
 {
-	struct hstate *h = &default_hstate;
+	struct hstate *h;
+
 	if (!hugepages_supported())
 		return;
-	seq_printf(m,
-			"HugePages_Total:   %5lu\n"
-			"HugePages_Free:    %5lu\n"
-			"HugePages_Rsvd:    %5lu\n"
-			"HugePages_Surp:    %5lu\n"
-			"Hugepagesize:   %8lu kB\n",
-			h->nr_huge_pages,
-			h->free_huge_pages,
-			h->resv_huge_pages,
-			h->surplus_huge_pages,
-			1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
+
+	for_each_hstate(h) {
+		char prefix[16] = "";
+
+		if (h != &default_hstate) {
+			unsigned int order = huge_page_order(h) + PAGE_SHIFT;
+			char suffix = '_';
+
+			if (order >= 30) {
+				order -= 30;
+				suffix = 'G';
+			} else if (order >= 20) {
+				order -= 20;
+				suffix = 'M';
+			} else if (order >= 10) {
+				order -= 10;
+				suffix = 'k';
+			}
+
+			snprintf(prefix, sizeof(prefix), "_%lu%c",
+				 1UL << order, suffix);
+		}
+
+		seq_printf(m,
+			"HugePages%s_Total:   %5lu\n"
+			"HugePages%s_Free:    %5lu\n"
+			"HugePages%s_Rsvd:    %5lu\n"
+			"HugePages%s_Surp:    %5lu\n"
+			"Hugepagesize%s:   %8lu kB\n",
+			prefix, h->nr_huge_pages,
+			prefix, h->free_huge_pages,
+			prefix, h->resv_huge_pages,
+			prefix, h->surplus_huge_pages,
+			prefix, 1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
+	}
 }
 
 int hugetlb_report_node_meminfo(int nid, char *buf)
-- 
2.13.6

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Michal Hocko]

On Mon 13-11-17 16:03:02, Roman Gushchin wrote:
> Currently we display some hugepage statistics (total, free, etc)
> in /proc/meminfo, but only for default hugepage size (e.g. 2Mb).
> 
> If hugepages of different sizes are used (like 2Mb and 1Gb on x86-64),
> /proc/meminfo output can be confusing, as non-default sized hugepages
> are not reflected at all, and there are no signs that they are
> existing and consuming system memory.

Yes this sucks but we do have per numa node per h-state stats in sysfs
already /sys/devices/system/node/node*/hugepages

I know it is another source of the information but is there any reason
you cannot use it?
-- 
Michal Hocko
SUSE Labs

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Michal Hocko]

On Mon 13-11-17 16:03:02, Roman Gushchin wrote:
> Currently we display some hugepage statistics (total, free, etc)
> in /proc/meminfo, but only for default hugepage size (e.g. 2Mb).
> 
> If hugepages of different sizes are used (like 2Mb and 1Gb on x86-64),
> /proc/meminfo output can be confusing, as non-default sized hugepages
> are not reflected at all, and there are no signs that they are
> existing and consuming system memory.

Yes this sucks but we do have per numa node per h-state stats in sysfs
already /sys/devices/system/node/node*/hugepages

I know it is another source of the information but is there any reason
you cannot use it?
-- 
Michal Hocko
SUSE Labs

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 05:11:02PM +0100, Michal Hocko wrote:
> On Mon 13-11-17 16:03:02, Roman Gushchin wrote:
> > Currently we display some hugepage statistics (total, free, etc)
> > in /proc/meminfo, but only for default hugepage size (e.g. 2Mb).
> > 
> > If hugepages of different sizes are used (like 2Mb and 1Gb on x86-64),
> > /proc/meminfo output can be confusing, as non-default sized hugepages
> > are not reflected at all, and there are no signs that they are
> > existing and consuming system memory.
> 
> Yes this sucks but we do have per numa node per h-state stats in sysfs
> already /sys/devices/system/node/node*/hugepages
> 
> I know it is another source of the information but is there any reason
> you cannot use it?

Hi, Michal!

In my case, I didn't know in advance, that hugetlb pages are preallocated,
and spent some time trying to find "magically disappeared" several Gb of memory,
which are not reflected in any /proc/[meminfo,vmstat] counters.

IMO, /proc/meminfo should give a user a high-level overview of memory usage
in the system, without a need to look into other places. Of course, we always
have some amount of unaccounted memory, but it shouldn't be measured in Gb,
as in this case.

If you're worried about adding counters which will be 0 most of the time
for most users, we can print them conditionally, only if total number of
corresponding pages is not 0.

Thanks!

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 05:11:02PM +0100, Michal Hocko wrote:
> On Mon 13-11-17 16:03:02, Roman Gushchin wrote:
> > Currently we display some hugepage statistics (total, free, etc)
> > in /proc/meminfo, but only for default hugepage size (e.g. 2Mb).
> > 
> > If hugepages of different sizes are used (like 2Mb and 1Gb on x86-64),
> > /proc/meminfo output can be confusing, as non-default sized hugepages
> > are not reflected at all, and there are no signs that they are
> > existing and consuming system memory.
> 
> Yes this sucks but we do have per numa node per h-state stats in sysfs
> already /sys/devices/system/node/node*/hugepages
> 
> I know it is another source of the information but is there any reason
> you cannot use it?

Hi, Michal!

In my case, I didn't know in advance, that hugetlb pages are preallocated,
and spent some time trying to find "magically disappeared" several Gb of memory,
which are not reflected in any /proc/[meminfo,vmstat] counters.

IMO, /proc/meminfo should give a user a high-level overview of memory usage
in the system, without a need to look into other places. Of course, we always
have some amount of unaccounted memory, but it shouldn't be measured in Gb,
as in this case.

If you're worried about adding counters which will be 0 most of the time
for most users, we can print them conditionally, only if total number of
corresponding pages is not 0.

Thanks!

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Dave Hansen]

On 11/13/2017 08:03 AM, Roman Gushchin wrote:
> To solve this problem, let's display stats for all hugepage sizes.
> To provide the backward compatibility let's save the existing format
> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.

Is there something keeping you from using the sysfs version of this
information?

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Dave Hansen]

On 11/13/2017 08:03 AM, Roman Gushchin wrote:
> To solve this problem, let's display stats for all hugepage sizes.
> To provide the backward compatibility let's save the existing format
> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.

Is there something keeping you from using the sysfs version of this
information?

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
> > To solve this problem, let's display stats for all hugepage sizes.
> > To provide the backward compatibility let's save the existing format
> > for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
> 
> Is there something keeping you from using the sysfs version of this
> information?

Just answered the same question to Michal.

In two words: it would be nice to have a high-level overview of
memory usage in the system in /proc/meminfo. 

Thanks!

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
> > To solve this problem, let's display stats for all hugepage sizes.
> > To provide the backward compatibility let's save the existing format
> > for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
> 
> Is there something keeping you from using the sysfs version of this
> information?

Just answered the same question to Michal.

In two words: it would be nice to have a high-level overview of
memory usage in the system in /proc/meminfo. 

Thanks!

--
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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Dave Hansen]

On 11/13/2017 10:11 AM, Roman Gushchin wrote:
> On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
>> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
>>> To solve this problem, let's display stats for all hugepage sizes.
>>> To provide the backward compatibility let's save the existing format
>>> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
>>
>> Is there something keeping you from using the sysfs version of this
>> information?
> 
> Just answered the same question to Michal.
> 
> In two words: it would be nice to have a high-level overview of
> memory usage in the system in /proc/meminfo. 

I don't think it's worth cluttering up meminfo for this, imnho.

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Dave Hansen]

On 11/13/2017 10:11 AM, Roman Gushchin wrote:
> On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
>> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
>>> To solve this problem, let's display stats for all hugepage sizes.
>>> To provide the backward compatibility let's save the existing format
>>> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
>>
>> Is there something keeping you from using the sysfs version of this
>> information?
> 
> Just answered the same question to Michal.
> 
> In two words: it would be nice to have a high-level overview of
> memory usage in the system in /proc/meminfo. 

I don't think it's worth cluttering up meminfo for this, imnho.

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Mike Kravetz]

On 11/13/2017 10:17 AM, Dave Hansen wrote:
> On 11/13/2017 10:11 AM, Roman Gushchin wrote:
>> On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
>>> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
>>>> To solve this problem, let's display stats for all hugepage sizes.
>>>> To provide the backward compatibility let's save the existing format
>>>> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
>>>
>>> Is there something keeping you from using the sysfs version of this
>>> information?
>>
>> Just answered the same question to Michal.
>>
>> In two words: it would be nice to have a high-level overview of
>> memory usage in the system in /proc/meminfo. 
> 
> I don't think it's worth cluttering up meminfo for this, imnho.

I tend to agree that it would be better not to add additional huge page
sizes here.  It may not seem too intrusive to (potentially) add one extra
set of entries for GB huge pages on x86.  However, other architectures
such as powerpc or sparc have several several huge pages sizes that could
potentially be added here as well.  Although, in practice one does tend
to use a single huge pages size.  If you change the default huge page
size, then those entries will be in /proc/meminfo.

-- 
Mike Kravetz

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Mike Kravetz]

On 11/13/2017 10:17 AM, Dave Hansen wrote:
> On 11/13/2017 10:11 AM, Roman Gushchin wrote:
>> On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
>>> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
>>>> To solve this problem, let's display stats for all hugepage sizes.
>>>> To provide the backward compatibility let's save the existing format
>>>> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
>>>
>>> Is there something keeping you from using the sysfs version of this
>>> information?
>>
>> Just answered the same question to Michal.
>>
>> In two words: it would be nice to have a high-level overview of
>> memory usage in the system in /proc/meminfo. 
> 
> I don't think it's worth cluttering up meminfo for this, imnho.

I tend to agree that it would be better not to add additional huge page
sizes here.  It may not seem too intrusive to (potentially) add one extra
set of entries for GB huge pages on x86.  However, other architectures
such as powerpc or sparc have several several huge pages sizes that could
potentially be added here as well.  Although, in practice one does tend
to use a single huge pages size.  If you change the default huge page
size, then those entries will be in /proc/meminfo.

-- 
Mike Kravetz

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 10:30:10AM -0800, Mike Kravetz wrote:
> On 11/13/2017 10:17 AM, Dave Hansen wrote:
> > On 11/13/2017 10:11 AM, Roman Gushchin wrote:
> >> On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
> >>> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
> >>>> To solve this problem, let's display stats for all hugepage sizes.
> >>>> To provide the backward compatibility let's save the existing format
> >>>> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
> >>>
> >>> Is there something keeping you from using the sysfs version of this
> >>> information?
> >>
> >> Just answered the same question to Michal.
> >>
> >> In two words: it would be nice to have a high-level overview of
> >> memory usage in the system in /proc/meminfo. 
> > 
> > I don't think it's worth cluttering up meminfo for this, imnho.
> 
> I tend to agree that it would be better not to add additional huge page
> sizes here.  It may not seem too intrusive to (potentially) add one extra
> set of entries for GB huge pages on x86.  However, other architectures
> such as powerpc or sparc have several several huge pages sizes that could
> potentially be added here as well.  Although, in practice one does tend
> to use a single huge pages size.  If you change the default huge page
> size, then those entries will be in /proc/meminfo.

I do agree that it might add some unnecessary verbosity if these sizes
are not used, but if they are, this information is super-useful.
So, might be a conditional printing will work here?

Or, at least, some total counter, e.g. how much memory is consumed
by hugetlb pages?

Thanks!

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 10:30:10AM -0800, Mike Kravetz wrote:
> On 11/13/2017 10:17 AM, Dave Hansen wrote:
> > On 11/13/2017 10:11 AM, Roman Gushchin wrote:
> >> On Mon, Nov 13, 2017 at 09:06:32AM -0800, Dave Hansen wrote:
> >>> On 11/13/2017 08:03 AM, Roman Gushchin wrote:
> >>>> To solve this problem, let's display stats for all hugepage sizes.
> >>>> To provide the backward compatibility let's save the existing format
> >>>> for the default size, and add a prefix (e.g. 1G_) for non-default sizes.
> >>>
> >>> Is there something keeping you from using the sysfs version of this
> >>> information?
> >>
> >> Just answered the same question to Michal.
> >>
> >> In two words: it would be nice to have a high-level overview of
> >> memory usage in the system in /proc/meminfo. 
> > 
> > I don't think it's worth cluttering up meminfo for this, imnho.
> 
> I tend to agree that it would be better not to add additional huge page
> sizes here.  It may not seem too intrusive to (potentially) add one extra
> set of entries for GB huge pages on x86.  However, other architectures
> such as powerpc or sparc have several several huge pages sizes that could
> potentially be added here as well.  Although, in practice one does tend
> to use a single huge pages size.  If you change the default huge page
> size, then those entries will be in /proc/meminfo.

I do agree that it might add some unnecessary verbosity if these sizes
are not used, but if they are, this information is super-useful.
So, might be a conditional printing will work here?

Or, at least, some total counter, e.g. how much memory is consumed
by hugetlb pages?

Thanks!

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Johannes Weiner]

On Mon, Nov 13, 2017 at 06:45:01PM +0000, Roman Gushchin wrote:
> Or, at least, some total counter, e.g. how much memory is consumed
> by hugetlb pages?

I'm not a big fan of the verbose breakdown for every huge page size.
As others have pointed out such detail exists elswhere.

But I do think we should have a summary counter for memory consumed by
hugetlb that lets you know how much is missing from MemTotal. This can
be large parts of overall memory, and right now /proc/meminfo will
give the impression we are leaking those pages.

Maybe a simple summary counter for everything set aside by the hugetlb
subsystem - default and non-default page sizes, whether they're used
or only reserved etc.?

Hugetlb 12345 kB

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Johannes Weiner]

On Mon, Nov 13, 2017 at 06:45:01PM +0000, Roman Gushchin wrote:
> Or, at least, some total counter, e.g. how much memory is consumed
> by hugetlb pages?

I'm not a big fan of the verbose breakdown for every huge page size.
As others have pointed out such detail exists elswhere.

But I do think we should have a summary counter for memory consumed by
hugetlb that lets you know how much is missing from MemTotal. This can
be large parts of overall memory, and right now /proc/meminfo will
give the impression we are leaking those pages.

Maybe a simple summary counter for everything set aside by the hugetlb
subsystem - default and non-default page sizes, whether they're used
or only reserved etc.?

Hugetlb 12345 kB

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Mike Kravetz]

On 11/13/2017 11:10 AM, Johannes Weiner wrote:
> On Mon, Nov 13, 2017 at 06:45:01PM +0000, Roman Gushchin wrote:
>> Or, at least, some total counter, e.g. how much memory is consumed
>> by hugetlb pages?
> 
> I'm not a big fan of the verbose breakdown for every huge page size.
> As others have pointed out such detail exists elswhere.
> 
> But I do think we should have a summary counter for memory consumed by
> hugetlb that lets you know how much is missing from MemTotal. This can
> be large parts of overall memory, and right now /proc/meminfo will
> give the impression we are leaking those pages.
> 
> Maybe a simple summary counter for everything set aside by the hugetlb
> subsystem - default and non-default page sizes, whether they're used
> or only reserved etc.?
> 
> Hugetlb 12345 kB

I would prefer this approach.  The 'trick' is coming up with a name or
description that is not confusing.  Unfortunately, we have to leave the
existing entries.  So, this new entry will be greater than or equal to
HugePages_Total. :(  I guess Hugetlb is as good of a name as any?

-- 
Mike Kravetz

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Mike Kravetz]

On 11/13/2017 11:10 AM, Johannes Weiner wrote:
> On Mon, Nov 13, 2017 at 06:45:01PM +0000, Roman Gushchin wrote:
>> Or, at least, some total counter, e.g. how much memory is consumed
>> by hugetlb pages?
> 
> I'm not a big fan of the verbose breakdown for every huge page size.
> As others have pointed out such detail exists elswhere.
> 
> But I do think we should have a summary counter for memory consumed by
> hugetlb that lets you know how much is missing from MemTotal. This can
> be large parts of overall memory, and right now /proc/meminfo will
> give the impression we are leaking those pages.
> 
> Maybe a simple summary counter for everything set aside by the hugetlb
> subsystem - default and non-default page sizes, whether they're used
> or only reserved etc.?
> 
> Hugetlb 12345 kB

I would prefer this approach.  The 'trick' is coming up with a name or
description that is not confusing.  Unfortunately, we have to leave the
existing entries.  So, this new entry will be greater than or equal to
HugePages_Total. :(  I guess Hugetlb is as good of a name as any?

-- 
Mike Kravetz

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Dave Hansen]

On 11/13/2017 11:10 AM, Johannes Weiner wrote:
> Maybe a simple summary counter for everything set aside by the hugetlb
> subsystem - default and non-default page sizes, whether they're used
> or only reserved etc.?

Yeah, one line is a lot more sane than 5 lines times all the extra
sizes.  It'll just be a matter of bikeshedding the name and whether it
should include the default pages being consumed or not.  I vote for:

	Hugetlb: "/sysfs FTW!" kB

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Dave Hansen]

On 11/13/2017 11:10 AM, Johannes Weiner wrote:
> Maybe a simple summary counter for everything set aside by the hugetlb
> subsystem - default and non-default page sizes, whether they're used
> or only reserved etc.?

Yeah, one line is a lot more sane than 5 lines times all the extra
sizes.  It'll just be a matter of bikeshedding the name and whether it
should include the default pages being consumed or not.  I vote for:

	Hugetlb: "/sysfs FTW!" kB

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Michal Hocko]

On Mon 13-11-17 16:33:05, Roman Gushchin wrote:
[...]
> IMO, /proc/meminfo should give a user a high-level overview of memory usage
> in the system, without a need to look into other places. Of course, we always
> have some amount of unaccounted memory, but it shouldn't be measured in Gb,
> as in this case.

Well, this is not so easy. There can be _a lot_ of unaccounted memory.
Gbs is not something unheard of (fs metadata directly allocated by the
page allocator, network buffers, you name it). Unlike those the hugetlb
requires an explicit admin interaction. Especially for the non-default
hugetlb page sizes.

-- 
Michal Hocko
SUSE Labs

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Michal Hocko]

On Mon 13-11-17 16:33:05, Roman Gushchin wrote:
[...]
> IMO, /proc/meminfo should give a user a high-level overview of memory usage
> in the system, without a need to look into other places. Of course, we always
> have some amount of unaccounted memory, but it shouldn't be measured in Gb,
> as in this case.

Well, this is not so easy. There can be _a lot_ of unaccounted memory.
Gbs is not something unheard of (fs metadata directly allocated by the
page allocator, network buffers, you name it). Unlike those the hugetlb
requires an explicit admin interaction. Especially for the non-default
hugetlb page sizes.

-- 
Michal Hocko
SUSE Labs

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Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 11:25:21AM -0800, Mike Kravetz wrote:
> On 11/13/2017 11:10 AM, Johannes Weiner wrote:
> > On Mon, Nov 13, 2017 at 06:45:01PM +0000, Roman Gushchin wrote:
> >> Or, at least, some total counter, e.g. how much memory is consumed
> >> by hugetlb pages?
> > 
> > I'm not a big fan of the verbose breakdown for every huge page size.
> > As others have pointed out such detail exists elswhere.
> > 
> > But I do think we should have a summary counter for memory consumed by
> > hugetlb that lets you know how much is missing from MemTotal. This can
> > be large parts of overall memory, and right now /proc/meminfo will
> > give the impression we are leaking those pages.
> > 
> > Maybe a simple summary counter for everything set aside by the hugetlb
> > subsystem - default and non-default page sizes, whether they're used
> > or only reserved etc.?
> > 
> > Hugetlb 12345 kB
> 
> I would prefer this approach.  The 'trick' is coming up with a name or
> description that is not confusing.  Unfortunately, we have to leave the
> existing entries.  So, this new entry will be greater than or equal to
> HugePages_Total. :(  I guess Hugetlb is as good of a name as any?

Yes, I like this approach too, and Hugetlb (in kB) sounds reasonable.
I'll post a new patch soon.

Re: [PATCH] mm: show stats for non-default hugepage sizes in /proc/meminfo

[Roman Gushchin]

On Mon, Nov 13, 2017 at 11:25:21AM -0800, Mike Kravetz wrote:
> On 11/13/2017 11:10 AM, Johannes Weiner wrote:
> > On Mon, Nov 13, 2017 at 06:45:01PM +0000, Roman Gushchin wrote:
> >> Or, at least, some total counter, e.g. how much memory is consumed
> >> by hugetlb pages?
> > 
> > I'm not a big fan of the verbose breakdown for every huge page size.
> > As others have pointed out such detail exists elswhere.
> > 
> > But I do think we should have a summary counter for memory consumed by
> > hugetlb that lets you know how much is missing from MemTotal. This can
> > be large parts of overall memory, and right now /proc/meminfo will
> > give the impression we are leaking those pages.
> > 
> > Maybe a simple summary counter for everything set aside by the hugetlb
> > subsystem - default and non-default page sizes, whether they're used
> > or only reserved etc.?
> > 
> > Hugetlb 12345 kB
> 
> I would prefer this approach.  The 'trick' is coming up with a name or
> description that is not confusing.  Unfortunately, we have to leave the
> existing entries.  So, this new entry will be greater than or equal to
> HugePages_Total. :(  I guess Hugetlb is as good of a name as any?

Yes, I like this approach too, and Hugetlb (in kB) sounds reasonable.
I'll post a new patch soon.

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