[Xen-devel] [PATCH 0/7] oxenstored: improve transaction conflict handling

[Jonathan Davies <jonathan.davies@xxxxxxxxxx>]

This patch series makes a substantial improvement to oxenstored's transaction
handling.

The original design of oxenstored assumed that a transaction would only ever
span a small subtree. In practice this is rarely the case and means that other
xenstore traffic overlapping with a transaction can cause it to fail with
EAGAIN. This leads to significant performance problems with toolstack operations
when there is a certain level of xenstore traffic coming from other sources.

Instead, we observe that, although the transaction may span a large subtree, it
is very unlikely to read or write the same keys as other xenstore traffic. This
observation leads to an improved transaction conflict-handling algorithm in
which the transaction is replayed to check it is serializable. This approach is
superior in performance.

The sixth patch is the main one that changes the way transaction conflicts are
handled. The first five patches prepare the way by performing some refactoring
and addition of infrastructure that allows for transactions to be replayed. The
seventh patch adds some extra logging.

Jonathan Davies (7):
  oxenstored: refactor putting response on wire
  oxenstored: remove some unused parameters
  oxenstored: refactor request processing
  oxenstored: keep track of each transaction's operations
  oxenstored: move functions that process simple operations
  oxenstored: replay transaction upon conflict
  oxenstored: log request and response during transaction replay

 tools/ocaml/xenstored/Makefile        |    1 +
 tools/ocaml/xenstored/connection.ml   |    5 +-
 tools/ocaml/xenstored/define.ml       |    1 +
 tools/ocaml/xenstored/oxenstored.conf |    1 +
 tools/ocaml/xenstored/process.ml      |  344 +++++++++++++++++++++------------
 tools/ocaml/xenstored/transaction.ml  |   21 +-
 tools/ocaml/xenstored/xenstored.ml    |    1 +
 7 files changed, 239 insertions(+), 135 deletions(-)

-- 
1.7.10.4


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