Obtain CPU usage in Windows NT/2000

The method for obtaining the CPU usage in Windows NT/2000 is different from that in Windows 9X. The "performance counter" is not used for obtaining the CPU usage in Windows NT/2000 ". Instead, it uses ntquerysysteminformation, an API function not publicly available in Ntdll. dll. For more information about its usage, see Article : How to obtain the system startup time in Windows NT/2000.

To calculate the CPU usage in Windows NT/2000, use the following formula:

Cpuusageinpercent = 100-(cputimen-CpuTimen-1-cputime0)/(systemtimen-SystemTimen-1-systemtime0)/numberofprocessors * 100

Here
CPU time is the idle time of the CPU (in milliseconds );
Systemtime is the system time (MS );
Numberofprocessors indicates the number of processors in the system;
0, 1, n indicates the number of samples (0 indicates the oldest sampling, 1 indicates the newest sampling, and N indicates the newest sampling );

The following describes the required parameter values for calling the ntquerysysteminformation function. First, obtain the number of processors. In the system_basic_information structure, there is a bkenumberprocessors Member, which is what we need.

# Define systembasicinformation 0

Typedef struct
{
DWORD dwunknown1;
Ulong ukemaximumincrement;
Ulong upagesize;
Ulong ummnumberofphysicalpages;
Ulong ummlowestphysicalpage;
Ulong ummhighestphysicalpage;
Ulong uallocationgranularity;
Pvoid plowestuseraddress;
Pvoid pmmhighestuseraddress;
Ulong ukeactiveprocessors;
Byte bkenumberprocessors;
Byte bunknown2;
Word wunknown3;
} System_basic_information;

Long status;
System_basic_information SBI;

Status = ntquerysysteminformation (systembasicinformation, & SBI, sizeof (SBI), 0 );

To implement multiple sampling, We need to query the cputime and systemtime values in a loop and store their old values in temporary variables. For how to get system time, see <a href = "http://www.vckbase.com/bbs/prime/viewprime_mng.asp? Id = 348 "> how to obtain the system startup time in Windows NT/2000 System </a>. The idle time of the CPU is stored in the liidletime Member of the system_performance_information structure.

# Define systemperformanceinformation 2

Typedef struct
{
Large_integer liidletime;
DWORD dwspare [76];
} System_performance_information;

Large_integer lioldidletime = {0, 0 };
Large_integer lioldsystemtime = {0, 0 };
System_performance_information SPI;

While (1 ){
Status = ntquerysysteminformation (systemtimeinformation, & STI, sizeof (STI), 0 );
Status = ntquerysysteminformation (systemperformanceinformation, & SPI, sizeof (SPI), 0 );

// Calculate the CPU usage here

Lioldidletime = SPI. liidletime;
Lioldsystemtime = STI. likesystemtime;

Sleep (1000 );
}