PS 8.0.27: Wrong Free buffers value?

MySQL & MariaDB Percona Distribution for MySQL
#1

Hi all,

Quick question.

I’ve raised innodb_lru_scan_depth variable value up to 8192 (don’t ask why, experiments) to see how it can impact multithreaded dump import performance.

But since I started this import, and done this command:
mysql -e "show engine innodb status\G" | grep 'Free buffers'

I see next values:

Free buffers       136889
Free buffers       138022
Free buffers       137668
Free buffers       137161
Free buffers       137576
Free buffers       137258
Free buffers       137462
Free buffers       138242
Free buffers       137385
Free buffers       137131
Free buffers       137923
Free buffers       138432
Free buffers       137883
Free buffers       137830
Free buffers       137752
Free buffers       137879
Free buffers       137419
Free buffers       137561
Free buffers       137180
Free buffers       137457
Free buffers       138534
Free buffers       137592
Free buffers       138085
Free buffers       137498
Free buffers       137072
Free buffers       138296
Free buffers       137379
Free buffers       137319
Free buffers       137459
Free buffers       137787

What is wrong? From what I understand it should be equal maximum to innodb_lru_scan_depth value?

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#2

innodb_lru_scan_depth “… influences the algorithms and heuristics for the flush operation for the buffer pool. … It specifies, per buffer pool instance, how far down the buffer pool LRU page list the page cleaner thread scans looking for dirty pages to flush.”

“Free buffers” is the number of pages in your buffer pool that are free to hold new data. The two are not directly related.

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#3

Ah. Now clear. Sorry for such lame question.

Topic is closed.

1 Like