>> Hi Sage,
>> Recently I tracked some single op, and found that the bufferlist::rebuild_aligned will cost some time that a litte longer.
>> The whole subop spend 7ms,and the pwritev spend 1.2ms, but the
>> rebuild_aligned cost 1.1ms.the test’s object length is 1M, Using
>> rados put. I think the bufferlist rebuild and align should not cost so much time. The os environment have vm.swappiness = 0 and have tcmalloc. Is this normal?
>>
>> 2016-10-14 11:50:48.131103 queue_transactions existing
>> 0x7f8900c302c0
>> osr(134.62s3 0x7f88ff458160)
>> 2016-10-14 11:50:48.132477 queue_transactions (writeahead) 3234
>> [Transaction(0x7f8907736000),Transaction(0x7f89077361c0)]
>>>> cost 1.1ms FileJournal::prepare_entry => bufferlist::
>>>> rebuild_aligned
>
>why do you think 1.1ms is cost from rebuild... there exists a lot of things. rebuild of course is a problem we need to resolve. but it won't be problem in hdd case since it's just memory copy.
i printed the timestamp on the path, and found the most time of 1.1ms spend in bufferlist::rebuild_aligned...
the 1M data of pwritev is write to page cache not on disk, maybe it let bufferlist aligned seem somewhat expensive...
>> 2016-10-14 11:50:48.133583 _journaled_ahead 0x7f88ff586ba0 seq 3234 osr(134.62s3 0x7f88ff458160) [Transaction(0x7f8907736000),Transaction(0x7f89077361c0)]
>> 2016-10-14 11:50:48.133620 queue_op 0x7f88ff586ba0 seq 3234 osr(134.62s3 0x7f88ff458160) 1051330 bytes (queue has 1 ops and 1051330 bytes)
>> 2016-10-14 11:50:48.133630 queueing ondisk 0x7f8903ab77c0
>> 2016-10-14 11:50:48.133654 _do_op 0x7f88ff586ba0 seq 3234
>> osr(134.62s3 0x7f88ff458160)/0x7f88ff458160 start
>> 2016-10-14 11:50:48.133669 _do_transaction on 0x7f8907736000
>> 2016-10-14 11:50:48.133685 remove
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#298
>> 2016-10-14 11:50:48.133754 lfn_unlink: clearing omap on
>> 3#134:461e3a1c:::testfile_4M:head#298 in cid 134.62s3_head
>> 2016-10-14 11:50:48.134526 remove
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#298 = 0
>> 2016-10-14 11:50:48.134557 _omap_setkeys
>> 134.62s3_head/3#134:46000000::::head#
>> 2016-10-14 11:50:48.134705 _omap_setkeys
>> 134.62s3_head/3#134:46000000::::head# = 0
>> 2016-10-14 11:50:48.134716 _do_transaction on 0x7f89077361c0
>> 2016-10-14 11:50:48.134723 _collection_move_rename
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#29a from
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#
>> 2016-10-14 11:50:48.134736 _set_replay_guard 3234.1.0 START
>> 2016-10-14 11:50:48.135859 _set_replay_guard 3234.1.0 done
>> 2016-10-14 11:50:48.136130 lfn_unlink: clearing omap on
>> 3#134:461e3a1c:::testfile_4M:head# in cid 134.62s3_head
>> 2016-10-14 11:50:48.136305 _close_replay_guard 3234.1.0
>> 2016-10-14 11:50:48.137023 _close_replay_guard 3234.1.0 done
>> 2016-10-14 11:50:48.137039 _collection_move_rename
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#29a from
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head# = 0
>> 2016-10-14 11:50:48.137057 write
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head# 0~1048576
>>>> cost 1.2ms pwritev
>> 2016-10-14 11:50:48.138255 write
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head# 0~1048576 = 1048576
>> 2016-10-14 11:50:48.138291 setattrs
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#
>> 2016-10-14 11:50:48.138313 setattrs
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head# = 0
>> 2016-10-14 11:50:48.138330 fgetattrs 70 getting 'hinfo_key'
>> 2016-10-14 11:50:48.138337 setattrs
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#
>> 2016-10-14 11:50:48.138357 setattrs
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head# = 0
>> 2016-10-14 11:50:48.138371 fgetattrs 70 getting '_'
>> 2016-10-14 11:50:48.138376 fgetattrs 70 getting 'snapset'
>> 2016-10-14 11:50:48.138381 fgetattrs 70 getting 'hinfo_key'
>> 2016-10-14 11:50:48.138386 setattrs
>> 134.62s3_head/3#134:461e3a1c:::testfile_4M:head#
>> 2016-10-14 11:50:48.138409 _do_op 0x7f88ff586ba0 seq 3234 r = 0,
>> finisher 0x7f8909398680 0
>> 2016-10-14 11:50:48.138420 _finish_op 0x7f88ff586ba0 seq 3234
>> osr(134.62s3 0x7f88ff458160)/0x7f88ff458160 lat 0.007306
>>
>> Than you, best regards
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