Re: Ceph MDS and hard links

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On Fri, Aug 3, 2018 at 8:53 PM Benjeman Meekhof <bmeekhof@xxxxxxxxx> wrote:
>
> Thanks, that's useful to know.  I've pasted the output you asked for
> below, thanks for taking a look.
>
> Here's the output of dump_mempools:
>
> {
>     "mempool": {
>         "by_pool": {
>             "bloom_filter": {
>                 "items": 4806709,
>                 "bytes": 4806709
>             },
>             "bluestore_alloc": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluestore_cache_data": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluestore_cache_onode": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluestore_cache_other": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluestore_fsck": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluestore_txc": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluestore_writing_deferred": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluestore_writing": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "bluefs": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "buffer_anon": {
>                 "items": 1303621,
>                 "bytes": 6643324694
>             },
>             "buffer_meta": {
>                 "items": 2397,
>                 "bytes": 153408
>             },
>             "osd": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "osd_mapbl": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "osd_pglog": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "osdmap": {
>                 "items": 8222,
>                 "bytes": 185840
>             },
>             "osdmap_mapping": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "pgmap": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "mds_co": {
>                 "items": 160660321,
>                 "bytes": 4080240182
>             },
>             "unittest_1": {
>                 "items": 0,
>                 "bytes": 0
>             },
>             "unittest_2": {
>                 "items": 0,
>                 "bytes": 0
>             }
>         },
>         "total": {
>             "items": 166781270,
>             "bytes": 10728710833
>         }
>     }
> }
>
> and heap_stats:
>
> MALLOC:    12418630040 (11843.3 MiB) Bytes in use by application
> MALLOC: +      1310720 (    1.2 MiB) Bytes in page heap freelist
> MALLOC: +    378986760 (  361.4 MiB) Bytes in central cache freelist
> MALLOC: +      4713472 (    4.5 MiB) Bytes in transfer cache freelist
> MALLOC: +     20722016 (   19.8 MiB) Bytes in thread cache freelists
> MALLOC: +     62652416 (   59.8 MiB) Bytes in malloc metadata
> MALLOC:   ------------
> MALLOC: =  12887015424 (12290.0 MiB) Actual memory used (physical + swap)
> MALLOC: +    309624832 (  295.3 MiB) Bytes released to OS (aka unmapped)
> MALLOC:   ------------
> MALLOC: =  13196640256 (12585.3 MiB) Virtual address space used
> MALLOC:
> MALLOC:         921411              Spans in use
> MALLOC:             20              Thread heaps in use
> MALLOC:           8192              Tcmalloc page size
>

mds does use 4GB memory for its cache, but there are 6GB memory used
by bufferlist. It seems like there is memory leak. Could you try
simple messenger (add "ms type = simple" to 'global' section of
ceph.conf)


> On Wed, Aug 1, 2018 at 10:31 PM, Yan, Zheng <ukernel@xxxxxxxxx> wrote:
> > On Thu, Aug 2, 2018 at 3:36 AM Benjeman Meekhof <bmeekhof@xxxxxxxxx> wrote:
> >>
> >> I've been encountering lately a much higher than expected memory usage
> >> on our MDS which doesn't align with the cache_memory limit even
> >> accounting for potential over-runs.  Our memory limit is 4GB but the
> >> MDS process is steadily at around 11GB used.
> >>
> >> Coincidentally we also have a new user heavily relying on hard links.
> >> This led me to the following (old) document which says "Hard links are
> >> also supported, although in their current implementation each link
> >> requires a small bit of MDS memory and so there is an implied limit
> >> based on your available memory. "
> >> (https://ceph.com/geen-categorie/cephfs-mds-status-discussion/)
> >>
> >> Is that statement still correct, could it potentially explain why our
> >> memory usage appears so high?  As far as I know this is a recent
> >> development and it does very closely correspond to a new user doing a
> >> lot of hardlinking.  Ceph Mimic 13.2.1, though we first saw the issue
> >> while still running 13.2.0.
> >>
> >
> > That statement is no longer correct.   what are output of  "ceph
> > daemon mds.x dump_mempools" and "ceph tell mds.x heap stats"?
> >
> >
> >> thanks,
> >> Ben
> >> _______________________________________________
> >> ceph-users mailing list
> >> ceph-users@xxxxxxxxxxxxxx
> >> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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