[Bug 253742] New: ksysguardd: inefficient read loop

[Ortwin Glück]

https://bugs.kde.org/show_bug.cgi?id=253742

           Summary: ksysguardd: inefficient read loop
           Product: kde
           Version: 4.4
          Platform: Gentoo Packages
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: minor
          Priority: NOR
         Component: general
        AssignedTo: unassigned-bugs at kde.org
        ReportedBy: odi at odi.ch


Version:           4.4 (using KDE 4.4.5) 
OS:                Linux

ksysguardd.c uses an ineffient loop to read from a fd. This causes 1 syscall
per byte. Look at the following strace:
select(5, [0 4], NULL, NULL, NULL)      = 1 (in [0])
read(0, "c", 1)                         = 1
read(0, "p", 1)                         = 1
read(0, "u", 1)                         = 1
read(0, "/", 1)                         = 1
read(0, "c", 1)                         = 1
read(0, "p", 1)                         = 1
read(0, "u", 1)                         = 1
read(0, "3", 1)                         = 1
read(0, "/", 1)                         = 1
read(0, "w", 1)                         = 1
read(0, "a", 1)                         = 1
read(0, "i", 1)                         = 1
read(0, "t", 1)                         = 1
read(0, "?", 1)                         = 1
read(0, "\n", 1)                        = 1
write(1, "CPU 4 Wait Load\t0\t100\t%\n", 24) = 24
write(1, "ksysguardd> ", 12)            = 12

Reproducible: Always


Actual Results:  
231     static int readCommand( int fd, char* cmdBuf, size_t len )
232     {
233     unsigned int i;
234     char c;
235     for ( i = 0; i < len; ++i )
236     {
237     int result = read( fd, &c, 1 );
238     if (result < 0)
239     return -1; /* Error */
240     
241     if (result == 0) {
242     if (i == 0)
243     return -1; /* Connection lost */
244     
245     break; /* End of data */
246     }
247     
248     if (c == '\n')
249     break; /* End of line */
250     
251     cmdBuf[ i ] = c;
252     }
253     cmdBuf[i] = '\0';
254     
255     return i;
256     } 


Reads from a fd should be buffered.

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