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Now, when we mount ext4 filesystem with '-o discard' option, we have to issue all the discard commands for the blocks to be deallocated and wait for the completion of the commands on the commit complete phase. Because this procedure might involve a lot of sequential combinations of issuing discard commands and waiting for that, the delay of this procedure might be too much long, even to 17.0s in our test, and it results in long commit delay and fsync() performance degradation. To reduce this kind of delay, instead of adding callback for each extent and handling all of them in a sequential manner on commit phase, we instead add a separate list of extents to free to the superblock and then process this list at once after transaction commits so that we can issue all the discard commands in a parallel manner like XFS filesystem. Finally, we could enhance the discard command handling performance. The result was such that 17.0s delay of a single commit in the worst case has been enhanced to 4.8s. Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Tested-by: Hobin Woo <hobin.woo@samsung.com> Tested-by: Kitae Lee <kitae87.lee@samsung.com> Reviewed-by: Jan Kara <jack@suse.cz>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.