SaaS-based application performance monitoring start-up New Relic, which has already raised $34.5 million in venture capital, has gotten a whopping $80 million in mezzanine financing to move into native mobile applications, open an office in Europe, add staff and prepare to IPO.

The handsome sum, which gives it a total of $115 million and a reported valuation of $750 million, comes largely from Insight Venture Partners and T Rowe Price, marking the first time since Twitter that the pair has funded a start-up together.

Other participants include Dragoneer Investment Group, Passport Ventures and the company's existing investors Allen & Company, Benchmark Capital, Trinity Ventures and Tenaya Capital.

New Relic says it saw 200% year-over-year revenue growth including 18 quarters of consecutive growth from playing in the data center and cloud markets monitoring deployed web applications implemented in Ruby, Java, .NET or PHP.

It also doubled its customer base, pushing the number to 35,000 active customer accounts in five years, adding over 1,200 paying customers in the December quarter.

It's supposed to be the industry's largest installed base for an application performance management solution. It does 85 billion metrics a day and a million app instances are sent to New Relic at any given time.

The money will help New Relic increase its enterprise footprint.

It says its widgetry has been adopted by thousands of companies worldwide, including significant deployments with ESPN, Nike and Sony. Collaboration, e-commerce, gaming and social media businesses such as Comcast, E*Trade, eHarmony, GitHub, Groupon, Mashable, MercadoLibre and Zumba also use New Relic to lower the costs of maintaining and optimizing business-critical software applications.

The company figures it's looking at a $20 billion market and that - with its unspoken "grander plans" beyond application performance management - it can be as "just as important as VMware or Salesforce.com.

New Relic CEO Lew Cirne sold Wily Technology, which monitored on-premise Java apps, to CA in 2006 for $375 million and started New Relic in 2008. In November, CA sued New Relic for patent infringement seeking "undisclosed damages" and an injunction to prevent misuse of its IP.

The three patents allegedly infringed were part of the Wily acquisition. CA said in a statement that it "will not allow its patents to be infringed, especially by those who have already profited by selling to us the very patents in question."