Hi I have a concern with how NetBSD FUSE hande nodes TTL and FORGET. When we create/mkdir/mknod/lookup a node, we get a TTL for it (this is the entry_valid field in struct fuse_entry_out). The kernel should not lookup the node again until the TTL expires. This means that once the TTL is expired, the kernel must do a lookup, again, and therefore that the previously obtained node should not be used. That suggests a FUSE FORGET can be sent for it as soon as (the kernel does not reference it AND TTL is expired). For now, NetBSD is lazy about the FUSE FORGET. It is sent when it reaches the vnode limit and needs to make room. This means there are a lot of stale nodes that remain in the kernel and in glusterfs, consuming memory. I can switch to a behavior where the FUSE FORGET are sent aggressively as soon as (kernel reference drops to 0 and TTL is expired), but this will cause a lot of useless FUSE messages, with an impact on the performance front. To make it clear, here is what we have with lazy FORGET policy: LOOKUP a INACTIVE a (ttl expires) LOOKUP a INACTIVE a (ttl expires) LOOKUP a ... And here is what I get wth aggressive FORGET policy LOOKUP a INACTIVE a (ttl expires) FORGET a <- extra useless FORGET LOOKUP a INACTIVE a (ttl expires) FORGET a <- extra useless FORGET LOOKUP a ... What do you think is the best approach? How does the Linux kernel handles the situation? -- Emmanuel Dreyfus http://hcpnet.free.fr/pubz manu@xxxxxxxxxx
