Linux Program Performance analysis tool Time+pstrace+grpof__linux

Http://www.cnblogs.com/me115/p/4605273.html

background

Developed a Redis data import tool using C + +
Import all table data from Oracle into Redis;
Not just data import, the original records in each Oracle, need to be processed by business logic,
and add an index (Redis collection);
When the tool is finished, performance is a bottleneck; optimization effect

2 Sample Data tests were used:
Sample Data a table 8,763 records;
Table B 940,279 Records;

Before optimization, a table is time-consuming 11.417s;
After optimization, a table takes 1.883s;

Gprof, Pstrace,time

Use the time tool to see how time-consuming each execution is, including user and system time;
Use Pstrace to print real-time operation, query process main system call, find the time consuming point;
Use the time-consuming summary of the GPROF statistics program to focus on optimizing the most time-consuming areas;
Use introduction:
1. All editing and connectivity options for g++ must be added-PG (the first day, because there is no-PG option at the junction, resulting in no statistical report);
2. After the execution of the program, this catalogue will produce gmon.out documents;
3.gprof Redistool gmou.out >, generate readable file, open the most time-consuming function of the focus of the study; optimization Process

Optimized before 11.417s:

Time./redistool im-a a.csv real    0m11.417s
user    0m6.035s
sys     0m4.782s (discovery of system calls is too long)

File Memory Mappings

The system call time is too long, mainly is the file reads and writes, the preliminary consideration is reads the file, invokes the API frequency too frequently;
Read the sample is a file fgets a row of reading, the use of file memory mapping mmap, you can directly manipulate the entire file memory fast; Log switch Advance

After improving the file reading and writing, found that the optimization effect is relatively limited (increased by about 2s); fgets is a C file read library function, compared to the system read (), is with the buffer, should not be too slow (people on the Web test, file memory mapping compared to fgets () can be faster than the previous order of magnitude, Feel the scene should be more special);

Then through the Pstrace tool found that log.dat open too many times, the original debug log switch is written to the back, resulting in the debug log will open the log file open ("Log.dat");
Put the log switch ahead; After the improvement, 3.53s

Time./redistool im a a.csv
real    0m3.530s
user    0m2.890s
sys     0m0.212s

vector space Pre-allocation

Subsequent through gprof analysis, a function of vector memory allocation more than a few times, and a number of replication times:
Improve the following line of code:

Vector <string> vsegment;

Use static vector variables and allocate memory in advance:

static vector <string> vsegment;
Vsegment.clear ();
static int ncount = 0;
if (0 = ncount)
{
    vsegment.reserve;
}
++ncount;

After optimization, upgrade to 2.286s

Real    0m2.286s
user    0m1.601s
sys     0m0.222s

Similarly, the member vectors in another class also use a pre-allocated space (in a constructor):

M_vtpipecmd.reserve (256);

After optimization, the promotion to 2.166s;

Real    0m2.166s
user    0m1.396s
sys     0m0.204s

function rewriting && inline

Continue executing the program, discovering that the Sqtoolstrsplitbych () function consumes too much, overwrites the entire function logic, and then inline the rewritten function:
After optimization, upgrade to 1.937s

Real    0m1.937s
user    0m1.301s
sys     0m0.186s

removing the debugger and optimizing the monitoring symbol

Finally, after removing debug and PG Debug symbols, the final effect is 1.883s;

Real    0m1.883s
user    0m1.239s
sys     0M0.191S

Meet production requirements

The last few steps appear to be the millisecond level of ascension, expanded to the full table data, the effect is very obvious;
After optimization, the production of a table is 152w, the import time is about 326s (~6 minutes);
Table B data 420w, import time is about 1103s (~18 minutes)

Posted by: Big CC | 28jun,2015
Blog: blog.me115.com [Subscribe]
Github: Big cc