Crash recovery, again

There’s one stage in InnoDB crash recovery where it reads log file, you know, this one:

InnoDB: Doing recovery: scanned up to log sequence number 354164119040
InnoDB: Doing recovery: scanned up to log sequence number 354169361920

On a machine with bigger logs it will start spending nearly 100% CPU somewhere in recv_scan_log_recs. Guess what it does…. -fno-inline builds to the rescue:

#0  mem_block_get_len at ./include/mem0mem.ic:86
#1  mem_heap_get_size at ./include/mem0mem.ic:591
#2  recv_scan_log_recs at log/log0recv.c:2727

And:

samples  %        symbol name
8467     72.9222  mem_heap_get_size
291       2.5062  recv_add_to_hash_table
95        0.8182  mem_block_get_len

To speak in layman’s terms, InnoDB does SUM(LENGTH(allocation)) on its relatively wide memory (tens, hundreds of thousands of entries) arena, FOR EVERY LOG SEGMENT, to make sure it didn’t run out of available 32GBs. Hehehe, lame.

As for now, I’ll just killed the check and have my recovery much much faster – finished in 3 minutes, what it wasn’t able to do in 30 before.

P.S. This is different from what I wrote before (and magic Yasufumi’s patch)
P.P.S. Now I got to learn to reuse LOG_DUMMY table during the recovery process, as it is next low hanging fruit there…

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