TLDR Tech / Practical
Linux kernel change causes excessive writes in PXC/Galera
An investigation into significant disk write activity on Percona XtraDB Cluster 8.0 systems running Debian 12 with Linux kernel 6.1 revealed a problem linked to the kernel's handling of large folios for mmapped Gcache files. This issue causes the system to track entire folios for mmapped updates instead of individual filesystem blocks, leading to substantial write amplification during the writeback of dirty data. Potential solutions include reducing the readahead size, using the EXT4 filesystem instead of XFS, or disabling Transparent Huge Pages.
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