[pve-devel] [PATCH pve-manager] 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.

We 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>
---
 PVE/API2/Ceph/OSD.pm | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/PVE/API2/Ceph/OSD.pm b/PVE/API2/Ceph/OSD.pm
index ded359904..5f7718b0a 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 +699,24 @@ __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 $memory;
+	if ($pid && $pid > 0) {
+	    open (my $SMAPS, '<', "/proc/$pid/smaps_rollup")
+		or die 'Could not open smaps_rollup for Ceph OSD';
+
+	    while (my $line = <$SMAPS>) {
+		if ($line =~ m/^Pss:\s+([0-9]+) kB$/) {
+		    $memory = $1 * 1024;
+		    last;
+		}
+	    }
+	}
 
 	my $data = {
 	    osd => {
-- 
2.39.2