Hi, I am working on something I have called "batched discard support" for Ext3 and Ext4 filesystems. Traditional discard support for filesystems like Ext4 has been implemented the way that whenever the file is unlinked the disk-space that the file was using is trimmed (discarded) by sb_issue_discard() to let the device know that this portion of disk is no longer in use by the filesystem and can be safely used for wear-leveling. However, this approach comes with very noticeable performance loss on most of SSD devices and LUN's I have the opportunity to test it on. The fact is, that bigger discard ranges are more efficient than smaller ones, so it make sense try to batch the ranges together wherever it is possible. I have introduced new filesystem independent ioctl (FITRIM) which can be used to send the "trim this portion of filesystem" command down to the filesystem which (if implemented) discards all free extents in that range. The implementation for Ext3 and Ext4 is complete and you can see it here: http://www.spinics.net/lists/linux-ext4/msg21050.html Why I am sending it here to linux-fsdevel is because I am introducing new fs independent ioctl and new member of super_operations (trim_fs) and we would like let you know about this approach (which any filesystem can take advantage from) and we would like your comment on this patch before we send it upstream. Thanks! -Lukas [PATCH] 9c8c3a5 Add ioctl FITRIM fs/ioctl.c | 39 +++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 8 ++++++++ 2 files changed, 47 insertions(+), 0 deletions(-) -- 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
