f682a398b2
The access cache is used during RCU-walk path lookups, so it is best to avoid locking if possible as taking a lock kills concurrency. The rbtree is not rcu-safe and cannot easily be made so. Instead we simply check the last (i.e. most recent) entry on the LRU list. If this doesn't match, then we return -ECHILD and retry in lock/refcount mode. This requires freeing the nfs_access_entry struct with rcu, and requires using rcu access primatives when adding entries to the lru, and when examining the last entry. Calling put_rpccred before kfree_rcu looks a bit odd, but as put_rpccred already provides rcu protection, we know that the cred will not actually be freed until the next grace period, so any concurrent access will be safe. This patch provides about 5% performance improvement on a stat-heavy synthetic work load with 4 threads on a 2-core CPU. Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com> |
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| .. | ||
| acpi | ||
| asm-generic | ||
| clocksource | ||
| crypto | ||
| drm | ||
| dt-bindings | ||
| keys | ||
| kvm | ||
| linux | ||
| math-emu | ||
| media | ||
| memory | ||
| misc | ||
| net | ||
| pcmcia | ||
| ras | ||
| rdma | ||
| rxrpc | ||
| scsi | ||
| sound | ||
| target | ||
| trace | ||
| uapi | ||
| video | ||
| xen | ||
| Kbuild | ||