thanks! i open the debug_bluefs to 10, but did not see the
"_should_compact_log" log when fio is writing the rbd...so how /offen
will BlueFS::sync_metadata() be called?
2017-08-29 21:19 GMT+08:00 Sage Weil <sweil@xxxxxxxxxx>:
> On Tue, 29 Aug 2017, zengran zhang wrote:
>> hi Sage,
>> I want to ask when will the bluefs log be compacted? I only sure
>> it will be compacted when umount the bluefs...
>> I see the log be compact when rocksdb call Dir.Fsync(), but want to
>> know how to trigger this...
>
> There is a heuristic for when it gets "too big":
>
> bool BlueFS::_should_compact_log()
> {
> uint64_t current = log_writer->file->fnode.size;
> uint64_t expected = _estimate_log_size();
> float ratio = (float)current / (float)expected;
> dout(10) << __func__ << " current 0x" << std::hex << current
> << " expected " << expected << std::dec
> << " ratio " << ratio
> << (new_log ? " (async compaction in progress)" : "")
> << dendl;
> if (new_log ||
> current < cct->_conf->bluefs_log_compact_min_size ||
> ratio < cct->_conf->bluefs_log_compact_min_ratio) {
> return false;
> }
> return true;
> }
>
> and the estimate for the (compacted) size is
>
> uint64_t BlueFS::_estimate_log_size()
> {
> int avg_dir_size = 40; // fixme
> int avg_file_size = 12;
> uint64_t size = 4096 * 2;
> size += file_map.size() * (1 + sizeof(bluefs_fnode_t));
> for (auto& p : block_all)
> size += p.num_intervals() * (1 + 1 + sizeof(uint64_t) * 2);
> size += dir_map.size() + (1 + avg_dir_size);
> size += file_map.size() * (1 + avg_dir_size + avg_file_size);
> return ROUND_UP_TO(size, super.block_size);
> }
>
> The default min_ratio is 5... so we compact when it's ~5x bigger than it
> needs to be.
>
> sage
>
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