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Message-ID: <20091018232918.GA7385@Krystal> Date: Sun, 18 Oct 2009 19:29:18 -0400 From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Cc: linux-kernel@...r.kernel.org Subject: Kernel RCU: shrink the size of the struct rcu_head Hi Paul, I noticed that you already discussed the possibility of shrinking the struct rcu_head by removing the function pointer. (http://kernel.org/pub/linux/kernel/people/paulmck/rcutodo.html) The ideas brought in so far require having per-callback lists, which involves a bit of management overhead and don't permit keeping the call_rcu() in cpu order. You might want to look into the Userspace RCU urcu-defer.c implementation, where I perform pointer encoding to compact the usual case, expected to be the same callback passed as parameter multiple times in a row to call_rcu(). This is very typical with multiple free() calls for different data structures next to each other. This typically keeps the size of the information to encode per callback down to a minimum: the size of a single pointer. It would be good to trace the kernel usage of call_rcu() to see if my assumption holds. I just thought I should tell you before you start looking at this issue further. Thanks, Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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