migration: faster savevm_state_handler_insert()

[PATCH v2 0/2] migration: faster savevm_state_handler_insert()

Scott Cheloha posted 2 patches 4 years, 6 months ago

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git fetch https://github.com/patchew-project/qemu tags/patchew/20191017205953.13122-1-cheloha@linux.vnet.ibm.com

Maintainers: Juan Quintela <quintela@redhat.com>, "Dr. David Alan Gilbert" <dgilbert@redhat.com>

migration/savevm.c | 35 ++++++++++++++++++++++++++++++-----
1 file changed, 30 insertions(+), 5 deletions(-)

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[PATCH v2 0/2] migration: faster savevm_state_handler_insert()

Posted by Scott Cheloha 4 years, 6 months ago

The savevm_state.handlers queue of SaveStateEntry objects is a
priority queue with an O(n) insertion cost.  This is makes startup
extremely slow when a VM has many such objects to register.  For
instance, a ppc64 VM with a large (8T+) maxmem needs to register tens
of thousands of SaveStateEntry handlers: startup for these VMs is
glacial.

If we track insertion points within the priority queue we can make
savevm_state_handler_insert() a constant-time operation with little
change to the module's code.  Startup times for VMs with many handlers
are dramatically improved as a result.

Changes since v1:
  * Split patch 1 into 2 patches.

Scott Cheloha (2):
  migration: add savevm_state_handler_remove()
  migration: savevm_state_handler_insert: constant-time element
    insertion

 migration/savevm.c | 35 ++++++++++++++++++++++++++++++-----
 1 file changed, 30 insertions(+), 5 deletions(-)

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2.23.0