On Feb 9, 2012, at 2:58 PM, Myklebust, Trond wrote: > On Thu, 2012-02-09 at 19:48 +0000, Adamson, Dros wrote: >>> >>>> I do have an implementation that doesn't need to walk the deviceid list by allowing a shared rpc_iostats struct between multiple rpc_clients (in addition to the current rpc_iostats structure), but that required adding locking and reference counting -- all for printing stats (obviously not what we want). >>> >>> This might be more in line with what we want. Note that it should be >>> easy to clone an rpc_client and then replace its rpc_iostats struct. I >>> don't think that needs any extra locking. We're already ignoring locking >>> here between different rpc_tasks, so throwing in different rpc_clients >>> to the mix will make no difference. >> >> Yeah, that's easy enough and i guess we could ignore locking, but we are still left with the same problem: how is this supposed to account for different mount points using the same nfs_client? nfs_client only has one rpc_client member. I doubt we want to make a hash lookup on nfs_server to get the right rpc_client (which could all use the same underlying xprt). >> >> Maybe it's time to move these stats into fs/nfs/ where they really belong? We could get rid of the hack that overloads procnum with opnum from inside the compound for v4+ and finally only show a specific mount's RPC stats. > > Actually, how about just adding a callback into struct rpc_call_ops > that, if it is defined, would be called instead of rpc_count_iostats(). > If you then modify rpc_count_iostats() to take the 'stats' variable as a > parameter, you can simply have the new callback call rpc_count_iostats > with the right arguments. Yeah, that could work! On my walk home from the cafe (they always seem to help) I came up with a slightly different strategy: - remove the cl_metrics (struct rpc_iostats) member from rpc_clnt - add an *optional* rpc_iostats pointer to rpc_task (ignored if NULL) - allocate one rpc_iostats structure (really array of structs, but you know what I mean) per nfs_server structure - when setting up rpc_tasks in nfs-land, pass the correct rpc_iostats with this strategy we don't accumulate stats when they aren't ever used (like an rpc_client used for mount protocol). again, only NFS uses the rpc stats interface. I kind of like this better than a callback, but either way is fine with me. Which way would you prefer? -dros > > -- > Trond Myklebust > Linux NFS client maintainer > > NetApp > Trond.Myklebust@xxxxxxxxxx > www.netapp.com >
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