Performace Counters in Sharepoint

Objects and Counters	Problem	Resolution Options
Processor
Processor - % Processor Time	Over 75-85% This shows processor usage over time. If this is consistently too high, you may find performance is adversely affected. Remember to count "Total" in multiprocessor systems. You can measure the utilization on each processor also, to ensure balanced performance between cores.	Upgrade processor Increase number of processors Add additional server(s)
Disk
Avg. Disk Queue Length	Gradually increasing, system not in a steady state and queue is backing up This shows the average number of both read and write requests that were queued for the selected disk during the sample interval. A bigger disk queue length may not be a problem as long as disk reads/writes are not suffering and the system is working in a steady state without expanding queuing.	Increase number or speed of disks Change array configuration to stripe Move some data to an alternative server
% Idle Time	Less than 90%	Increase number of disks Move data to an alternative disk or server
% Free Space	Less than 30%	Increase number of disks Move data to an alternative disk or server
Memory
Available Mbytes	Less than 2GB on a Web server. This shows how much physical memory is available for allocation. Insufficient memory leads to excessive use of the page file and an increase in the number of page faults per second.	Add memory. Note: SQL Server available memory will be low, by design, and does not always indicate a problem.
Cache Faults/sec	Greater than 1 This counter shows the rate at which faults occur when a page is sought in the file system cache and is not found.	Add memory Increase cache speed or size if possible Move data to an alternative disk or server
Pages/sec	Greater than 10 This counter shows the rate at which pages are read from or written to disk to resolve hard page faults. If this increases, it indicates system-wide performance problems.	Add memory
Paging File
% Used and % Used Peak	The server paging file, sometimes called the swap file, holds "virtual" memory addresses on disk. Page faults occur when a process has to stop and wait while required "virtual" resources are retrieved from disk into memory. These will be more frequent if the physical memory is inadequate.	Add memory
NIC
Total Bytes/sec	Over 40-50% of network capacity. This is the rate at which data is sent and received via the network interface card.	Investigate further by monitoring Bytes received/sec and Bytes Sent/sec. Reassess network interface card speed Check number, size, and usage of memory buffers
Process
Working Set	Greater than 80% of total memory. This counter indicates the current size (in bytes) of the working set for a given process. This memory is reserved for the process, even if it is not being used.	Add memory
% Processor Time	Over 75-85%.	Increase number of processors Redistribute workload to additional servers
ASP.NET
Application Pool Recycles	Several per day, causing intermittent slowness.	Make sure that you have not implemented settings that automatically recycle the application pool unnecessarily throughout the day.
Requests Queued	Hundreds or thousands of requests queued.	Implement additional Web servers The default maximum for this counter is 5,000, and you can change this setting in the Machine.config file
Request Wait Time	As the number of wait events increases, users will experience degraded page rendering performance.	Implement additional Web servers
Requests Rejected	Greater than 0	Implement additional Web servers

References:
http://technet.microsoft.com/en-us/library/ff758658.aspx