Can anyone provide suggestions on benchmarking safety management system?

In answer to your second question, I would probably seek objective data with which to measure the results of the safety management system, such as lost time accident frequency or fatalities covering both employees and contractors.  Those could be benchmarked with at least a measure of consistency and objectivity across organisations in the same/similar industry. 

As to your first question, performance starting with earnings before interest and tax might help in ensuring inter-organisation consistency ignoring differences arising from financial capital structure. 

Dear Sir I am very happy to see your question. It is very relevant now days for all industry specially productive link manufacturing industry. It has direct relationship between safety management system and performance of units.It means better safety management must be higher performance causing high productivity. PCG,CLI

I very agreed with you Paresh Chandra Ghosh. Thanks for your idea.

Thank you Dr please consult shell safety benchmark manual it will be clear to you what ideal safety bench mark is required to improve productivity,safety and health. Remember health is wealth good health can only produce. thank you with kind regards . PCG.CLI

While event data may help indicate the performance of a SMS system with respect to high frequency low consequence events it will not help with low frequency high consequence events which the major hazard industries have to deal with. We need to be confident that the SMS is fit for purpose and is being complied with. The former comes from ensuring that it follows a respected SMS standard and the latter from planned monitoring. 

Most organisations are taking an integrated approach to management as it is the same common structures and processes that determine all aspects of an organisation's performance. A universal management system standard is the simplest and most effective solution and provides full advice. Download a free copy now of MSS 1000:2014 (top of list) via http://www.thecqi.org/Community/Special-Interest-Groups-SIGs/Integrated-Management-Group/Research-and-reports/ 

Dear Dato Dr. Mohamad Nasir Saludin These links could help you.

They talk about OHS performance and how to evaluate it. They mention, among others, the safety management system

Article Assessment of occupational health and safety performance eva...

Article A novel tool for evaluating occupational health and safety p...

Article Development of a Preliminary Model for Evaluating Occupation...