Changing kernel configuration options related to the SquashFS decompression

Hello, While working on the change proposal https://fedoraproject.org/wiki/Changes/OptimizeSquashFS I discovered that several kernel configuration options are set sub-optimally in Fedora. In RHEL 8, the optimal configuration is used. If we set those options to match RHEL 8, a performance improvement could be achieved while reading the SquashFS filesystem. Below you can see an excerpt from the configuration help: Set in RHEL 8: SQUASHFS_FILE_DIRECT       Directly decompress file data into the page cache.       Doing so can significantly improve performance because       it eliminates a memcpy and it also removes the lock contention       on the single buffer. SQUASHFS_DECOMP_MULTI_PERCPU       By default Squashfs uses a single decompressor but it gives       poor performance on parallel I/O workloads when using multiple CPU       machines due to waiting on decompressor availability.       This decompressor implementation uses a maximum of one       decompressor per core.  It uses percpu variables to ensure       decompression is load-balanced across the cores. Set in Fedora: SQUASHFS_DECOMP_SINGLE       Traditionally Squashfs has used single-threaded decompression.       Only one block (data or metadata) can be decompressed at any       one time.  This limits CPU and memory usage to a minimum. SQUASHFS_FILE_CACHE       Decompress file data into an intermediate buffer and then       memcopy it into the page cache. The SquashFS filesystem is used on installation medium. So making the change I propose should improve the user experience during installation. It should also improve the user experience while booting from Fedora Live image. Kind regards, -- Bohdan Khomutskyi Software engineer Red Hat