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For tablespaces that do not reside on spinning storage, it does not make sense to attempt to write nearby pages when writing out dirty pages from the InnoDB buffer pool. It is actually detrimental to performance and to the life span of flash ROM storage. With this change, MariaDB will detect whether an InnoDB file resides on solid-state storage. The detection has been implemented for Linux and Microsoft Windows. For other systems, we will err on the safe side and assume that files reside on SSD. As part of this change, we will reduce the number of fstat() calls when opening data files on POSIX systems and slightly clean up some file I/O code. FIXME: os_is_sparse_file_supported() on POSIX works in a destructive manner. Thus, we can only invoke it when creating files, not when opening them. For diagnostics, we introduce the column ON_SSD to the table INFORMATION_SCHEMA.INNODB_TABLESPACES_SCRUBBING. The table INNODB_SYS_TABLESPACES might seem more appropriate, but its purpose is to reflect the contents of the InnoDB system table SYS_TABLESPACES, which we would like to remove at some point. On Microsoft Windows, querying StorageDeviceSeekPenaltyProperty sometimes returns ERROR_GEN_FAILURE instead of ERROR_INVALID_FUNCTION or ERROR_NOT_SUPPORTED. We will silently ignore also this error, and assume that the file does not reside on SSD. On Linux, the detection will be based on the files /sys/block/*/queue/rotational and /sys/block/*/dev. Especially for USB storage, it is possible that /sys/block/*/queue/rotational will wrongly report 1 instead of 0. fil_node_t::on_ssd: Whether the InnoDB data file resides on solid-state storage. fil_system_t::ssd: Collection of Linux block devices that reside on non-rotational storage. fil_system_t::create(): Detect ssd on Linux based on the contents of /sys/block/*/queue/rotational and /sys/block/*/dev. fil_system_t::is_ssd(dev_t): Determine if a Linux block device is non-rotational. Partitions will be identified with the containing block device by assuming that the least significant 4 bits of the minor number identify a partition, and that the "partition number" of the entire device is 0. |
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