Hi, On 09/08/2009 12:23 PM, Jens Axboe wrote:
From: Theodore Ts'o<tytso@xxxxxxx> Originally, MAX_WRITEBACK_PAGES was hard-coded to 1024 because of a concern of not holding I_SYNC for too long. (At least, that was the comment previously.) This doesn't make sense now because the only time we wait for I_SYNC is if we are calling sync or fsync, and in that case we need to write out all of the data anyway. Previously there may have been other code paths that waited on I_SYNC, but not any more. According to Christoph, the current writeback size is way too small, and XFS had a hack that bumped out nr_to_write to four times the value sent by the VM to be able to saturate medium-sized RAID arrays. This value was also problematic for ext4 as well, as it caused large files to be come interleaved on disk by in 8 megabyte chunks (we bumped up the nr_to_write by a factor of two). So, in this patch, we make the MAX_WRITEBACK_PAGES a tunable, max_writeback_mb, and set it to a default value of 128 megabytes. http://bugzilla.kernel.org/show_bug.cgi?id=13930 Signed-off-by: "Theodore Ts'o"<tytso@xxxxxxx> Signed-off-by: Jens Axboe<jens.axboe@xxxxxxxxxx>
Would be nice to update doc files like Documentation/sysctl/vm.txt Documentation/filesystems/proc.txt as well. -- Best Regards, Artem Bityutskiy (Артём Битюцкий) -- 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
