I've become interested in this topic, as I'm also running MySQL with O_DIRECT and innodb_file_per_table. Out of curiosity, I immediately ran xfs_bmap on a moderately sized table space (34GB). It listed around 30000 fragments, on average one for every MB. I want to report what happened then: A flurry of activity started on both disks (root/swap lives on one of them, the data volume containing the MySQL files on another) and lasted for about two minutes. Afterwards, all memory previously allocated to the file cache has become free, and also everything XFS seems to keep buffered internally (I think it's called SReclaimable) was released. Swap usage increased only slightly. dmesg was silent during that time. This is a 2.6.32-358.2.1.el6.x86_64 kernel with xfsprogs 3.1.1 (CentOS 6.4). The machine has 64GB of RAM (2 NUMA nodes) and 24 (virtual) cores. Is this known behavior of xfs_bmap? -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
