Avi Kivity 6b747f4673 database: avoid creating thread in make_directory_for_column_family() ...

make_directory_for_column_family() is used in a parallel_for_each() in
parse_system_tables(). Because parallel_for_each does not preempt
in the initial execution of its input function, and because each thread
allocates 128k for the stack, we end up allocating many hundreds of
megabytes if there are many tables.

This happens early during boot and will only cause problems if
there are 5,000 tables per gigabyte of shard memory, and unlikely
combination that will probably fail later, but still it is better to
avoid unnecessary large allocations.

This was developed in order to fix #6003, until it was discovered that
c020b4e5e2 ("logalloc: increase capacity of _regions vector
outside reclaim lock") is the real fix.

Message-Id: <20200313093603.1366502-1-avi@scylladb.com>

2020-03-13 13:46:45 +02:00

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