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Fix #5232

osd: slow peering due to pg log rewrites

Added by Stefan Priebe over 6 years ago. Updated about 6 years ago.

Status:
Resolved
Priority:
Urgent
Assignee:
Category:
OSD
Target version:
Start date:
06/02/2013
Due date:
% Done:

0%

Source:
other
Tags:
Backport:
Reviewed:
Affected Versions:
ceph-qa-suite:
Pull request ID:

Description

I noticed that since cuttlefish the osd recovery process is extremely slow. Also client I/o gets stalled to the recovering osd ending up in slow request log messages.

Things I noticed:
- recovering osd uses 100-200% CPU until recovered
- nearly no disk I/o from that osd
- under bobtail I had much lower CPU usage and high disk I/o (which makes sense)
- recovering from a simple osd restart (getting changed objects since stop) is awful slow even my cluster was only degraded by 0.1% (24tb/3repl) took 10-20min
- I'm using xfs

This is a major blocker as recovering is nearly impossible.

Used version current upstream/cuttlefish

I've provided sage a gdb threads bt all.

Greets
Stefan

gdb.txt.gz (31.9 KB) Sage Weil, 06/02/2013 09:38 AM

ceph-osd.23.tar.gz (1.83 MB) Stefan Priebe, 06/02/2013 11:32 AM


Related issues

Related to Ceph - Bug #5238: osd: slow recovery (uselessly dirtying pg logs during peering) Resolved 06/03/2013

Associated revisions

Revision baa1c86e
Added by Samuel Just about 6 years ago

Merge remote-tracking branch 'upstream/wip-log-rewrite-sam'

Fixes: #5232
Reviewed-by: Sage Weil <>

History

#1 Updated by Sage Weil over 6 years ago

this thread?

No symbol table info available.
#1  0x00007fb90be5d1f5 in ?? () from /usr/lib/libleveldb.so.1
No symbol table info available.
#2  0x00007fb90be4781a in ?? () from /usr/lib/libleveldb.so.1
No symbol table info available.
#3  0x00007fb90be47c3d in ?? () from /usr/lib/libleveldb.so.1
No symbol table info available.
#4  0x000000000079a75a in LevelDBStore::LevelDBWholeSpaceIteratorImpl::seek_to_first(std::string const&) ()
No symbol table info available.
#5  0x0000000000798b1f in LevelDBStore::LevelDBTransactionImpl::rmkeys_by_prefix (this=0x2b4f02c0, prefix=...)
    at os/LevelDBStore.cc:141
        it = {<std::tr1::__shared_ptr<KeyValueDB::IteratorImpl, (__gnu_cxx::_Lock_policy)2>> = {_M_ptr = 0x36889740, 
            _M_refcount = {_M_pi = 0x31ab5b20}}, <No data fields>}
#6  0x000000000078a9f6 in DBObjectMap::clear_header (this=0x328ab00, header=
DWARF-2 expression error: DW_OP_reg operations must be used either alone or in conjuction with DW_OP_piece.
) at os/DBObjectMap.cc:1158
        keys = {_M_t = {
            _M_impl = {<std::allocator<std::_Rb_tree_node<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >> = {<__gnu_cxx::new_allocator<std::_Rb_tree_node<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >> = {<No data fields
>}, <No data fields>}, 
              _M_key_compare = {<std::binary_function<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool>> = {<No data fields>}, <No data fields>}, _M_header = {
                _M_color = 7894675, _M_parent = 0x7fb904ac73b8, _M_left = 0x7fb90be11fe0, _M_right = 0x0}, 
              _M_node_count = 13107200}}}
#7  0x000000000078af8a in DBObjectMap::_clear (this=0x328ab00, header=
DWARF-2 expression error: DW_OP_reg operations must be used either alone or in conjuction with DW_OP_piece.
) at os/DBObjectMap.cc:597
        parent = {<std::tr1::__shared_ptr<DBObjectMap::_Header, (__gnu_cxx::_Lock_policy)2>> = {_M_ptr = 0x3cb0780, _M_refcount = {
              _M_pi = 0x2e08da00}}, <No data fields>}
        __PRETTY_FUNCTION__ = "int DBObjectMap::_clear(std::tr1::shared_ptr<DBObjectMap::_Header>, std::tr1::shared_ptr<KeyValueDB::TransactionImpl>)" 
#8  0x000000000078b63c in DBObjectMap::clear (this=0x328ab00, hoid=<value optimized out>, spos=<value optimized out>)
    at os/DBObjectMap.cc:583
        t = {<std::tr1::__shared_ptr<KeyValueDB::TransactionImpl, (__gnu_cxx::_Lock_policy)2>> = {_M_ptr = 0x2b4f02c0, 
            _M_refcount = {_M_pi = 0x369a6e80}}, <No data fields>}
        header = {<std::tr1::__shared_ptr<DBObjectMap::_Header, (__gnu_cxx::_Lock_policy)2>> = {_M_ptr = 0x3cb0780, _M_refcount = {
              _M_pi = 0x2e08da00}}, <No data fields>}
        __PRETTY_FUNCTION__ = "virtual int DBObjectMap::clear(const hobject_t&, const SequencerPosition*)" 
        r = <value optimized out>
#9  0x000000000073a0a6 in FileStore::lfn_unlink (this=0x31be000, cid=
DWARF-2 expression error: DW_OP_reg operations must be used either alone or in conjuction with DW_OP_piece.
) at os/FileStore.cc:350
        path = {<std::tr1::__shared_ptr<CollectionIndex::Path, (__gnu_cxx::_Lock_policy)2>> = {_M_ptr = 0x32e05920, _M_refcount = {
              _M_pi = 0x31ab5ac0}}, <No data fields>}
        exist = 1
        st = {st_dev = 64770, st_ino = 1610612898, st_nlink = 1, st_mode = 33188, st_uid = 0, st_gid = 0, __pad0 = 0, st_rdev = 0, 
          st_size = 4194304, st_blksize = 4096, st_blocks = 8200, st_atim = {tv_sec = 1369771413, tv_nsec = 196604128}, st_mtim = {
            tv_sec = 1370120522, tv_nsec = 795389833}, st_ctim = {tv_sec = 1370120522, tv_nsec = 795389833}, __unused = {0, 0, 0}}
        index = {<std::tr1::__shared_ptr<CollectionIndex, (__gnu_cxx::_Lock_policy)2>> = {_M_ptr = 0x3b873c0, _M_refcount = {
              _M_pi = 0x29fa4120}}, <No data fields>}
        r = 0
        __PRETTY_FUNCTION__ = "int FileStore::lfn_unlink(coll_t, const hobject_t&, const SequencerPosition&)" 
        __func__ = "lfn_unlink" 
#10 0x000000000073a334 in FileStore::_remove (this=0x31be000, cid=
DWARF-2 expression error: DW_OP_reg operations must be used either alone or in conjuction with DW_OP_piece.
) at os/FileStore.cc:2882
        r = <value optimized out>
#11 0x0000000000765ef1 in FileStore::_do_transaction (this=<value optimized out>, t=<value optimized out>, 
    op_seq=<value optimized out>, trans_num=<value optimized out>) at os/FileStore.cc:2408
        cid = {static META_COLL = {static META_COLL = <same as static member of an already seen type>, str = {
              static npos = 18446744073709551615, 
              _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, 
                _M_p = 0x3197258 "meta"}}}, str = {static npos = 18446744073709551615, 
            _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, 
              _M_p = 0x2fa64a38 "4.de0_head"}}}
        oid = {oid = {name = {static npos = 18446744073709551615, 
              _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, 
                _M_p = 0x2a116c48 "rbd_data.57f6766b8b4567.", '0' <repeats 14 times>, "17"}}}, snap = {
            val = 18446744073709551614}, hash = 252288480, max = false, pool = 4, nspace = {static npos = 18446744073709551615, 
            _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, 
              _M_p = 0xc80398 ""}}, key = {static npos = 18446744073709551615, 
            _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>}, 
              _M_p = 0xc80398 ""}}}
        op = <value optimized out>
        r = <value optimized out>
        i = {p = {bl = 0x35163620, ls = 0x35163620, off = 98, p = {_M_node = 0x31be3920}, p_off = 98}, sobject_encoding = false, 
          pool_override = -1, use_pool_override = false, replica = false, _tolerate_collection_add_enoent = false}
        spos = {seq = 174858271, trans = 0, op = 0}
        __PRETTY_FUNCTION__ = "unsigned int FileStore::_do_transaction(ObjectStore::Transaction&, uint64_t, int)" 
#12 0x0000000000769af1 in FileStore::_do_transactions (this=0x31be000, tls=..., op_seq=174858271, handle=0x7fb904ac8ce0)
    at os/FileStore.cc:2151
        r = 201801232
        trans_num = 0
#13 0x0000000000769d74 in FileStore::_do_op (this=0x31be000, osr=0x2a2ff900, handle=...) at os/FileStore.cc:1985
        o = 0x2ae2f7d0
        r = <value optimized out>
#14 0x0000000000847f91 in ThreadPool::worker (this=0x31bea08, wt=<value optimized out>) at common/WorkQueue.cc:119
        tp_handle = {cct = 0x31a2000, hb = 0x42ff450, grace = 60, suicide_grace = 180}
        item = 0x2a2ff900
        wq = 0x31beb90
        ss = <incomplete type>
        hb = 0x42ff450

it's removing an rbd data object, but stuck in the leveldb iterator?

#2 Updated by Sage Weil over 6 years ago

stefan: can you also do

ceph --admin-daemon /var/run/ceph/ceph-osd.NNN.asok config set debug_ms 1
ceph --admin-daemon /var/run/ceph/ceph-osd.NNN.asok config set debug_osd 20
ceph --admin-daemon /var/run/ceph/ceph-osd.NNN.asok config set debug_filestore 20

to capture some logging when the osd is eating cpu?

thanks!

#3 Updated by Stefan Priebe over 6 years ago

Attached you'll find a log with debugging enabled in betweek and two new gdb thread all traces.

#4 Updated by Stefan Priebe over 6 years ago

May be a hint or just luck i could reduce the effect and time to recover by lowering osd op threads to 2 (default) instead of 4 i had normally.

But there are still slow requests.

#5 Updated by Sage Weil over 6 years ago

  • Status changed from New to Verified

This looks to me like a lot of time is being spent in leveldb clearing and rewriting the pglog. This is probably just due to a naive PG::write_log()...?

#6 Updated by Sage Weil over 6 years ago

even so, it seems like a lot of time is spent just in the removal phase.. perhaps there is something not quite right with the removal of old keys?

#7 Updated by Sage Weil over 6 years ago

Stefan, are there any non-default options for in your ceph.conf that might affect pg log size? How many pgs do you have per osd?

#8 Updated by Stefan Priebe over 6 years ago

No config changes except the minimum right now. Before I just had changed the osd op thread count.

4096 pgs 24 osds 6 hosts replication level 3

#9 Updated by Stefan Priebe over 6 years ago

Should I post the config?

#10 Updated by Sage Weil over 6 years ago

  • Subject changed from Osd hangs I/o gets stalled while recovering to osd: slow peering due to pg log rewrites

#11 Updated by Ian Colle over 6 years ago

  • Status changed from Verified to In Progress
  • Assignee set to Samuel Just

#12 Updated by Samuel Just over 6 years ago

  • Tracker changed from Bug to Fix
  • Target version set to v0.66

#13 Updated by Sage Weil over 6 years ago

  • translation missing: en.field_story_points set to 3.00

#14 Updated by Stefan Priebe over 6 years ago

This one misses cuttlefish for backport?

#15 Updated by Samuel Just about 6 years ago

  • Status changed from In Progress to Resolved

#16 Updated by Samuel Just about 6 years ago

This won't get backported. Some mitigating patches did go into cuttlefish. Also, there is wip_cuttlefish_compact_on_startup. fridudad_ on irc tried it, and it appeared to work (peering went quickly). Not sure how long it will take to compact leveldb on an OSD backing a radosgw workload. It also hasn't been tested much. (You need osd_compact_leveldb_on_mount to actually cause compaction on osd startup with that branch.)

#17 Updated by Stefan Priebe about 6 years ago

I'm fridudad ;-) Peering works fine but recovery does not. In my initial text of this tracker i also mentioned recovery as the main problem and not peering. Should i open a new report?

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