Hi, > On Tue, Aug 30, 2022 at 08:57:21AM +0800, Wang Yugui wrote: > > Hi, > > > > > On Mon, Aug 29, 2022 at 10:26:20AM +0800, Wang Yugui wrote: > > > > Hi, > > > > > > > > I saw some info about hybird xfs wih ssd/hdd by realtime subvol. > > > > > > > > Hybrid XFS―Using SSDs to Supercharge HDDs at Facebook > > > > https://www.usenix.org/conference/srecon19asia/presentation/shamasunder > > > > > > > > There are some questions about how to control the data to save into > > > > normal vol or realtime subvol firstly. > > > > > > > > 1, man xfsctl > > > > here is XFS_XFLAG_REALTIME in man xfsctl of xfsprogs 5.0 , > > > > but there is no XFS_XFLAG_REALTIME in xfsprogs 5.14/5.19. > > > > xfsctl(XFS_XFLAG_REALTIME) will be removed in the further? > > > > > > It's been a while since XFS uses FS_XFLAG features directly, so, what you're > > > specifically looking for is FS_XFLAG_REALTIME. xfsprogs today only has a > > > preprocessor define: > > > > > > #define XFS_XFLAG_REALTIME FS_XFLAG_REALTIME > > > > > > FS_XFLAG_REALTIME is part of the xfs realtime, unlikely it's going away without > > > the realtime filesystems going first, so, unlikely it's gonna happen. > > > > > > > > > > > 2, Is there some tool to do xfsctl(XFS_XFLAG_REALTIME)? > > > > > > You can use xfs_io's chattr command to add/remote the REALTIME attribute of a > > > file. > > > > > > > > > > > > > > 3, we build a xfs filesystem with 1G device and 1G rtdev device. and > > > > then we can save 2G data into this xfs filesystem. > > > > Sorry, I cheched again. > > This is a xfs filesystem with 2G device and 2G rtdev device > > > > > > Is there any tool/kernel option/kernel patch to control the data to save > > > > into normal vol or realtime subvol firstly? > > > > > > I didn't watch the talk you mentioned above, but when use an rt device, you > > > don't use the 'normal' one then the rt later, or vice-versa, the rt-device is > > > used to store data blocks for those files marked with the xattr above. For those > > > files you want to store in the realtime device, you should add the above xattr > > > to them. > > > > Although I still fail to check/set the attr by 'lsattr/chattr', but I > > can check the free space of 'normal' and realtime subvol now. > > > > # xfs_db -c sb -c p /dev/sdb8 |grep 'fdblocks\|frextents' > > typedef struct xfs_sb { > > ... > > uint64_t sb_fdblocks; /* free data blocks */ > > uint64_t sb_frextents; /* free realtime extents */ > > ... > > } > > > > And based the info from Carlos Maiolino > > > > FB were running a modified kernel that selected the rt dev based on > > the initial allocation size. Behaviour for them was predictable > > because they also controlled the application that was storing the > > data. See: > > > > https://lore.kernel.org/linux-xfs/20171128215527.2510350-1-rwareing@xxxxxx/ > > > > With a dirty patch below for test only , Now realtime subvol will be used > > as I expected, and that can be confirmed by > > #xfs_db -c sb -c p /dev/sdb8 |grep 'fdblocks\|frextents'. > > mkfs.xfs -d rtinherit=1... 'mkfs.xfs -d rtinherit=1' works very well. Thanks a lot. I noticed that 'reflink not supported with realtime devices' both in mkfs.xfs and in kernel/xfs(c14632ddac98 xfs: don't allow reflink + realtime filesystems). Is this a limit of current design? or we just disable reflink when realtime devices just for QoS/realtime? Best Regards Wang Yugui (wangyugui@xxxxxxxxxxxx) 2022/08/31
