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The CIO layer processes hardware events that indicate that a channel path has become available by performing a scan of available subchannels using the Store Subchannel (STSCH) instruction. Performing too many STSCH instructions in a tight loop can cause high Hypervisor overhead which can negatively impact the performance of the virtual machine as a whole. This patch reduces the number of STSCH instructions performed while processing a resource accessibility event and while varying a CHPID online. In both cases, Linux first performs a STSCH instruction on each unused subchannel to see if the subchannel has become available. If the STSCH instruction indicates that the subchannel is available, a full evaluation of this subchannel is scheduled. Since the full evaluation includes performing a STSCH instruction, the initial STSCH is unnecessary and can be removed. Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com> Reviewed-by: Sebastian Ott <sebott@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> |
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| Makefile | ||