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authorChuck Lever <chuck.lever@oracle.com>2009-12-03 15:58:56 -0500
committerTrond Myklebust <Trond.Myklebust@netapp.com>2009-12-03 15:58:56 -0500
commit206a134b4d8abf57cd34dffacf993869355b9aac (patch)
treeffe4724ce1957243de3eaa2e123b25c883c53412 /include
parentdd47f96c077b4516727e497e4b6fd47a06778c0a (diff)
SUNRPC: Check explicitly for tk_status == 0 in call_transmit_status()
The success case, where task->tk_status == 0, is by far the most frequent case in call_transmit_status(). The default: arm of the switch statement in call_transmit_status() handles the 0 case. default: was moved close to the top of the switch statement in call_transmit_status() under the theory that the compiler places object code for the earliest arms of a switch statement first, making the CPU do less work. The default: arm of a switch statement, however, is executed only after all the other cases have been checked. Even if the compiler rearranges the object code, the default: arm is the "last resort", meaning all of the other cases have been explicitly exhausted. That makes the current arrangement about as inefficient as it gets for the common case. To fix this, add an explicit check for zero before the switch statement. That forces the compiler to do the zero check first, no matter what optimizations it might try to do to the switch statement. Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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