Bug 70511
| Summary: | [libc] When fread(3)ing with buffering turned off, many syscalls invoked. | ||
|---|---|---|---|
| Product: | Base System | Reporter: | Dan Ponte <dcp1990> |
| Component: | kern | Assignee: | freebsd-bugs (Nobody) <bugs> |
| Status: | Open --- | ||
| Severity: | Affects Only Me | CC: | bdrewery, uau |
| Priority: | Normal | ||
| Version: | 5.2.1-RELEASE | ||
| Hardware: | Any | ||
| OS: | Any | ||
For bugs matching the following criteria: Status: In Progress Changed: (is less than) 2014-06-01 Reset to default assignee and clear in-progress tags. Mail being skipped |
When calling fread and buffering turned off, a read() syscall is made for each byte. With large limits, this may take a while and is very inefficient. Fix: Change __srefill() in stdio to read blocks at a time, instead of one byte. How-To-Repeat: In python, enter the following command: t=file('bigfile', 'r', 0).read(10000000) , replacing 'bigfile' with a large file. Notice how it takes a while to run. Now, start Python with truss and enter the same, and notice the flood of read() syscalls.