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'. diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index f4cc8a1aaeb4..d19e0fa34c1a 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -868,6 +868,9 @@ xfs_init_new_inode( flags |= XFS_ILOG_DEV; break; case S_IFREG: + if (xfs_has_realtime(ip->i_mount)) + ip->i_diflags |= XFS_DIFLAG_REALTIME; + fallthrough; case S_IFDIR: if (pip && (pip->i_diflags & XFS_DIFLAG_ANY)) xfs_inode_inherit_flags(ip, pip); Thanks a lot. Best Regards Wang Yugui (wangyugui@xxxxxxxxxxxx) 2022/08/30
