[pve-devel] [PATCH manager v3] api: ceph: improve reporting of ceph OSD memory usage

[Stefan Hanreich]

Currently we are using the MemoryCurrent property of the OSD service
to determine the used memory of a Ceph OSD. This includes, among other
things, the memory used by buffers [1]. Since BlueFS uses buffered
I/O, this can lead to extremely high values shown in the UI.

Instead we are now reading the PSS value from the proc filesystem,
which should more accurately reflect the amount of memory currently
used by the Ceph OSD.

Aaron and I decided on PSS over RSS, since this should give a better
idea of used memory - particularly when using a large amount of OSDs
on one host, since the OSDs share some of the pages.

[1] https://www.kernel.org/doc/Documentation/cgroup-v1/memory.txt

Signed-off-by: Stefan Hanreich <s.hanreich at proxmox.com>
Tested-by: Aaron Lauterer <a.lauterer at proxmox.com>
---
Changes from v2:
* closing the file handle after using it
* improved error message when failing to open proc file
* add hint in the UI that we are using PSS
* mentioned Aaron's involvement in commit message

Changes from v1:
 * now returns 0 instead of null in case of stopped OSDs in order to
 preserve backwards compatibility

 PVE/API2/Ceph/OSD.pm            | 21 ++++++++++++++++-----
 www/manager6/ceph/OSDDetails.js |  2 +-
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/PVE/API2/Ceph/OSD.pm b/PVE/API2/Ceph/OSD.pm
index ded359904..389802971 100644
--- a/PVE/API2/Ceph/OSD.pm
+++ b/PVE/API2/Ceph/OSD.pm
@@ -687,13 +687,10 @@ __PACKAGE__->register_method ({

 	my $raw = '';
 	my $pid;
-	my $memory;
 	my $parser = sub {
 	    my $line = shift;
 	    if ($line =~ m/^MainPID=([0-9]*)$/) {
 		$pid = $1;
-	    } elsif ($line =~ m/^MemoryCurrent=([0-9]*|\[not set\])$/) {
-		$memory = $1 eq "[not set]" ? 0 : $1;
 	    }
 	};

@@ -702,12 +699,26 @@ __PACKAGE__->register_method ({
 	    'show',
 	    "ceph-osd\@${osdid}.service",
 	    '--property',
-	    'MainPID,MemoryCurrent',
+	    'MainPID',
 	];
 	run_command($cmd, errmsg => 'fetching OSD PID and memory usage failed', outfunc => $parser);

 	$pid = defined($pid) ? int($pid) : undef;
-	$memory = defined($memory) ? int($memory) : undef;
+
+	my $memory = 0;
+	if ($pid && $pid > 0) {
+	    open (my $SMAPS, '<', "/proc/$pid/smaps_rollup")
+		or die "failed to read PSS memory-stat from process - $!\n";
+
+	    while (my $line = <$SMAPS>) {
+		if ($line =~ m/^Pss:\s+([0-9]+) kB$/) {
+		    $memory = $1 * 1024;
+		    last;
+		}
+	    }
+
+	    close $SMAPS;
+	}

 	my $data = {
 	    osd => {
diff --git a/www/manager6/ceph/OSDDetails.js b/www/manager6/ceph/OSDDetails.js
index f0765d4fe..3b1c1d9c0 100644
--- a/www/manager6/ceph/OSDDetails.js
+++ b/www/manager6/ceph/OSDDetails.js
@@ -148,7 +148,7 @@ Ext.define('PVE.CephOsdDetails', {
 				{
 				    xtype: 'text',
 				    name: 'mem_usage',
-				    text: gettext('Memory usage'),
+				    text: gettext('Memory usage (PSS)'),
 				    renderer: Proxmox.Utils.render_size,
 				},
 				{
--
2.39.2