DragonFlyBSD

As I came from FreeBSD I already faced ccache a little over ZFS. When ccache is almost full it starts freeing space, and when it does so (on ZFS) it stucks in zio->* state for a long time perusing disk.

HAMMER2 behaves very bad in this case too: * we have free mem (like 600Mb); * ccache hangs in chnmem state; * disk is idle; * writes are heavily penalized, disk is slow; * console is full of:

Dec 18 22:16:25 kernel: Warning: cache_resolve: ncp '4cfd2287d50b992cca713202e76553-14712.manifest.rm..474328.XXXXXX' was unlinked
Dec 18 22:16:25 kernel: kern_rename: retry due to gen on: "4cfd2287d50b992cca713202e76553-14712.manifest.rm..474328.XXXXXX" -> "4cfd2287d50b992cca713202e76553-14712.manifest.rm..474377.XXXXXX"
Dec 18 22:16:25 kernel: Warning: cache_resolve: ncp '1afbb983f96488451e95ae9de240a4-87227.o.rm..474856.XXXXXX' was unlinked
Dec 18 22:16:25 kernel: kern_rename: retry due to gen on: "1afbb983f96488451e95ae9de240a4-87227.o.rm..474856.XXXXXX" -> "1afbb983f96488451e95ae9de240a4-87227.o.rm..474352.XXXXXX"
Dec 18 22:16:34 kernel: Warning: cache_resolve: ncp '8dc566823e04be58a3e8dab71cba61-68692.o.rm..474856.XXXXXX' was unlinked
Dec 18 22:16:34 kernel: kern_rename: retry due to gen on: "8dc566823e04be58a3e8dab71cba61-68692.o.rm..474856.XXXXXX" -> "8dc566823e04be58a3e8dab71cba61-68692.o.rm..474352.XXXXXX"
Dec 18 22:16:42 kernel: [diagnostic] cache_lock_shared: blocked on 0xffffffe10a97e430 00000001 "8dc566823e04be58a3e8dab71cba61-68692.d.rm..474856.XXXXXX"
Dec 18 22:16:42 kernel: [diagnostic] cache_lock: blocked on 0xffffffe108d04120 00000001 "efc494c16cb3457c3e959e4e44e51e-3156639.o.rm..474328.XXXXXX"
Dec 18 22:16:42 kernel: [diagnostic] cache_lock_shared: unblocked 8dc566823e04be58a3e8dab71cba61-68692.d.rm..474856.XXXXXX after 0 secs
Dec 18 22:16:42 kernel: [diagnostic] cache_lock: unblocked efc494c16cb3457c3e959e4e44e51e-3156639.o.rm..474328.XXXXXX after 8 secs
Dec 18 22:16:42 kernel: Warning: cache_resolve: ncp 'efc494c16cb3457c3e959e4e44e51e-3156639.o.rm..474328.XXXXXX' was unlinked
Dec 18 22:16:42 kernel: kern_rename: retry due to gen on: "efc494c16cb3457c3e959e4e44e51e-3156639.o.rm..474328.XXXXXX" -> "efc494c16cb3457c3e959e4e44e51e-3156639.o.rm..474377.XXXXXX"
Dec 18 22:16:47 kernel: Warning: cache_resolve: ncp 'c4bd7d4813f22726c2b45f6c8b7053-25838.manifest.rm..474856.XXXXXX' was unlinked
Dec 18 22:16:47 kernel: kern_rename: retry due to gen on: "c4bd7d4813f22726c2b45f6c8b7053-25838.manifest.rm..474856.XXXXXX" -> "c4bd7d4813f22726c2b45f6c8b7053-25838.manifest.rm..474352.XXXXXX"
Dec 18 22:17:01 kernel: Warning: cache_resolve: ncp '0ce9bbd7190adeccf1db7e582ff7d4-12275.manifest.rm..474352.XXXXXX' was unlinked