Messages in this thread | | | Date | Thu, 12 Mar 2015 09:52:07 +0000 | From | Al Viro <> | Subject | Re: [PATCH 2/9] inode: add IOP_NOTHASHED to avoid inode hash lock in evict |
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On Tue, Mar 10, 2015 at 03:45:17PM -0400, Josef Bacik wrote: > From: Dave Chinner <dchinner@redhat.com> > > Some filesystems don't use the VFS inode hash and fake the fact they > are hashed so that all the writeback code works correctly. However, > this means the evict() path still tries to remove the inode from the > hash, meaning that the inode_hash_lock() needs to be taken > unnecessarily. Hence under certain workloads the inode_hash_lock can > be contended even if the inode is never actually hashed. > > To avoid this, add an inode opflag to allow inode_hash_remove() to > avoid taking the hash lock on inodes have never actually been > hashed.
Why bother with flags, etc. when we could just do
static inline bool hlist_fake(struct hlist_node *h) { return h->pprev == &h->next; }
> - if (!inode_unhashed(inode)) > + if (!((inode->i_opflags & IOP_NOTHASHED) || inode_unhashed(inode)))
and turn this check into if (!inode_unhashed(inode) && !hlist_fake(&inode->i_hash))
instead?
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