libhrtime, Version 0.6.1
High-Resolution Process Timing for the Linux Kernel
Copyright (C) 2000, Nick Rasmussen nick@jive.org
Location: http://www.paradyn.org/projects/legacy/libhrtime/
This patch adds very low-overhead access to high-resolution process virtual time and, optionally, high-resolution virutalized user and system time. The timers are based on the CPU timestamp counter and can be read at memory access speeds. Low overhead access to high-resolution process time is critical many profiling and benchmarking applications.
While other systems have offered access to high-resolution process time, they have required access through a system call interface.
Our approach uses an extra per-pid entry, /proc/PID/hrtime, that contains timing values; these values can be mmapped into a user's address space. For convienience, a library is also provided that performs the mmaping and timer querying work for you.
These routines work both for a process timing itself and a process timing another process.
The library interface to get high-resolution timing information is:
int get_hrtime_struct(pid_t pid, volatile struct hrtime_struct **dest);
Map the given timing page.
int free_hrtime_struct(volatile struct hrtime_struct *hr);
Unmap the given timing page.
void get_hrtime(volatile struct hrtime_struct *hr, hrtime_t *dest);
Get the total wall time in ticks.
void get_hrvtime(volatile struct hrtime_struct *hr, hrtime_t *dest);
Get the total virtual time in ticks
void get_hrutime(volatile struct hrtime_struct *hr, hrtime_t *dest);
Get the total virtualized user time in ticks (only if CONFIG_HRUSTIME was
enabled)
void get_hrstime(volatile struct hrtime_struct *hr, hrtime_t *dest);
Get the total virtualized system time in ticks (only if CONFIG_HRUSTIME was
enabled)
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Run some test cases to see what the cumulative slowdown (in cycles per syscall) when CONFIG_HRUSTIME is enabled.
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Compute the timestamp difference between multiple CPUs in SMP boxes, and do all hrtime (wall time) operations with reference to CPU 0.
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Add support for other architectures.
-
Figure out what to do with threaded programs.
This work was done for the Paradyn Parallel Performance Tools project at the University of Wisconsin (http://www.cs.wisc.edu/paradyn/) and was initially inspired by the vtimer patch by dadkins@mit.edu and bsong@supertech.lcs.mit.edu.
libhrtime and the hrtime kernel patches can be considered public domain.