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

[Jonathan Davies <jonathan.davies@xxxxxxxxxx>]

On Fri, Mar 18, 2016 at 10:33:35AM -0400, Konrad Rzeszutek Wilk wrote:
> On Thu, Mar 17, 2016 at 05:51:08PM +0000, Jonathan Davies wrote:
> > 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.
> 
> All the patches have quite the Reviewed-by list already so I would think
> these can go in now?
> 
> Thought oddly I didn't see any discussion on xen-devel for this?

Indeed; we did a lot of testing internally before these patches were posted.

Jonathan

> > 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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> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel

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