Re: high memory usage in osd_pglog

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Hi Kalle,

We are not using EC. The cluster is 15.2.5, it was upgraded from Mimic in
July. What is odd is the pg_logs report by a dump is much lower than we see
in osd mempool stats.

Regards,

Rob

On Thu, Nov 26, 2020 at 12:11 AM Kalle Happonen <kalle.happonen@xxxxxx>
wrote:

> Hi Robert,
> This sounds very much like a big problem we had 2 weeks back.
>
>
> https://lists.ceph.io/hyperkitty/list/ceph-users@xxxxxxx/thread/EWPPEMPAJQT6GGYSHM7GIM3BZWS2PSUY/
>
> Are you running EC? Which version are you running? It would fit our
> narrative if you use EC and recently updated to 14.2.11+
>
> For some reason this memory use started growing a day after we updated to
> 14.2.13. Another case I read was 14.2.11 I think. We don't know if the
> pg_logs hadn't really been used before, or if each entry size just grew
> much larger after the update for some reason. We don't see this in our
> replicated pools.
>
> We significantly reduced the default pg_log amount from 3000->500. If your
> cluster is still up and pgs are healthy, this should be doable online.
> Sadly we couldn't support the memory usage, and OSD processes started to
> get OOM killed. We had to trim these logs offline, which sadly affected our
> production.
>
> Cheers,
> Kalle
>
>
> ----- Original Message -----
> > From: "Robert Brooks" <robert.brooks@xxxxxxxxxx>
> > To: "ceph-users" <ceph-users@xxxxxxx>
> > Sent: Wednesday, 25 November, 2020 20:23:05
> > Subject:  high memory usage in osd_pglog
>
> > We are seeing very high osd_pglog usage in mempools for ceph osds. For
> > example...
> >
> >    "mempool": {
> >        "bloom_filter_bytes": 0,
> >        "bloom_filter_items": 0,
> >        "bluestore_alloc_bytes": 41857200,
> >        "bluestore_alloc_items": 523215,
> >        "bluestore_cache_data_bytes": 50876416,
> >        "bluestore_cache_data_items": 1326,
> >        "bluestore_cache_onode_bytes": 6814080,
> >        "bluestore_cache_onode_items": 13104,
> >        "bluestore_cache_other_bytes": 57793850,
> >        "bluestore_cache_other_items": 2599669,
> >        "bluestore_fsck_bytes": 0,
> >        "bluestore_fsck_items": 0,
> >        "bluestore_txc_bytes": 29904,
> >        "bluestore_txc_items": 42,
> >        "bluestore_writing_deferred_bytes": 733191,
> >        "bluestore_writing_deferred_items": 96,
> >        "bluestore_writing_bytes": 0,
> >        "bluestore_writing_items": 0,
> >        "bluefs_bytes": 101400,
> >        "bluefs_items": 1885,
> >        "buffer_anon_bytes": 21505818,
> >        "buffer_anon_items": 14949,
> >        "buffer_meta_bytes": 1161512,
> >        "buffer_meta_items": 13199,
> >        "osd_bytes": 1962920,
> >        "osd_items": 167,
> >        "osd_mapbl_bytes": 825079,
> >        "osd_mapbl_items": 17,
> >        "osd_pglog_bytes": 14099381936,
> >        "osd_pglog_items": 134285429,
> >        "osdmap_bytes": 734616,
> >        "osdmap_items": 26508,
> >        "osdmap_mapping_bytes": 0,
> >        "osdmap_mapping_items": 0,
> >        "pgmap_bytes": 0,
> >        "pgmap_items": 0,
> >        "mds_co_bytes": 0,
> >        "mds_co_items": 0,
> >        "unittest_1_bytes": 0,
> >        "unittest_1_items": 0,
> >        "unittest_2_bytes": 0,
> >        "unittest_2_items": 0
> >    },
> >
> > Where roughly 14g is required for pg_logs. Cluster has 106 OSD and 2432
> > placement groups.
> >
> > The pg log count for placement groups is much less than 134285429 logs.
> >
> > Top counts are...
> >
> > 1486 1.41c
> > 883 7.3
> > 834 7.f
> > 683 7.13
> > 669 7.a
> > 623 7.5
> > 565 7.8
> > 560 7.1c
> > 546 7.16
> > 544 7.19
> >
> > Summing these gives 21594 pg logs.
> >
> > Overall the performance of the cluster is poor, OSD memory usage is high
> > (20-30G resident), and with a moderate workload we are seeing iowait on
> OSD
> > hosts. The memory allocated to caches appears to be low, I believe
> because
> > osd_pglog is taking most of the available memory.
> >
> > Regards,
> >
> > Rob
> >
> > --
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