POSIX Thread Libraries
All results were obtained by running the benchmarks on a PC with a dual Pentium Pro Processor. The Pentium Pro Processor is a 32-bit processor with the RISC technology. This processor uses dynamic execution, a combination of improved branch prediction, speculative execution and data flow analysis. The clock speed of the computer was 200MHz, and it was equipped with 64MB of memory and a 2GB hard disk.
The tests were all performed ten times and the mean of the measurements was taken as the result for the test. This result is an indication of the performance of the function being evaluated. We have considered average values, because they are more representative of the performance the user can obtain from the machine. Other authors consider minimum values, because they are supposed to be free from the influence of the operating system and other users. The tests were taken with only one user on the machine. All tests compared the performance obtained for Solaris threads, Provenzano threads (PT), FSU_Pthreads (FSUT), PC threads (PCT), CLthreads (CLT) and LinuxThreads (LT). Threads created in Solaris are permanently bound to an LWP to take full advantage of the hardware platform used.
The numbers presented in Figure 5 are the results of the thread-management measurements. All values are given in microseconds, except for granularity of parallelism where values are given in number of iterations. In general, it can be seen that user-level packages are more efficient than kernel-level packages and Solaris threads, since the threads are created on top of the operating system and are invisible to the kernel; however, these libraries are not useful for multi-threaded applications running on multiprocessor systems. This is true for Provenzano threads and FSU_Pthreads, although PC threads present more time-consuming results. Results for granularity of parallelism are shown for kernel-level libraries (Solaris, CLthreads and LinuxThreads); user-level libraries cannot execute multiple threads in more than one processor. Figure 5 shows how Solaris can take better advantage of multiprocessor architecture. Comparing thread execution and granularity of parallelism results, we can see that context switching is more time-consuming for Linux threading (CLthreads and LinuxThreads) than for Solaris threading. LinuxThreads can take better advantage of multiprocessor systems than CLthreads can.
Figure 6 depicts the results of synchronization management measurements. PC threads (PCT) is less efficient, although it is a user-level library. Results show that Provenzano threads is the best user-level library evaluated, and LinuxThreads is a good kernel-level library for use in Linux machines.
Our objective was to evaluate and compare the performance of five POSIX thread libraries available for Linux and how they compared with other operating systems, such as Solaris. Results were concentrated in thread-management and synchronization-management measurements. Primary results show Provenzano threads to be the best user-level library, and LinuxThreads is a good kernel-level library. Moreover, results show that context switching is more time-consuming for Linux threading (CLthreads and LinuxThreads) than for Solaris threading.
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