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IRIX Base Documentation 1998 November
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IRIX 6.5.2 Base Documentation November 1998.img
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catman
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thrash.z
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thrash
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1998-10-30
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67 lines
TTTTHHHHRRRRAAAASSSSHHHH((((1111)))) TTTTHHHHRRRRAAAASSSSHHHH((((1111))))
NNNNAAAAMMMMEEEE
thrash - thrash memory to explore paging behavior
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
tttthhhhrrrraaaasssshhhh [args]
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
_t_h_r_a_s_h will allocate a region of its virtual memory of a size given by
its arguments, and either randomly or sequentially access that memory in
order to explore the system paging behavior.
The amount of memory to thrash over is specified by a size flag followed
by an integer argument, whose units are determined by the particular size
flag used. The flag may be -m, for megabytes, -p, for pages; or -k for
kilobytes. An additional argument of -s implies sequential thrashing;
the default is random. Another optional argument, -n count, gives the
number of references to make before exiting; it defaults to 10000. An
optional argument -w followed by an integer time tells thrash to sleep
for ``time'' seconds after thrashing, but before exiting.
Once the memory is allocated, _t_h_r_a_s_h prints a message on stdout saying
how much it is using, and then proceeds to thrash over it.
UUUUSSSSAAAAGGGGEEEE
_t_h_r_a_s_h can be used, in conjunction with _c_v_u_s_a_g_e and _s_q_u_e_e_z_e to determine
the approximate available working memory on a system. To do so, run the
command:
_s_s_u_s_a_g_e _t_h_r_a_s_h -_m _4
which asks _t_h_r_a_s_h to use about 4 MB of memory. When the command
completes, the resource usage of _t_h_r_a_s_h is printed; the value labeled
majf gives the number of major page faults it took, that is the number of
faults that required a physical read. When run on a machine with a large
amount of physical memory, this value is the number of faults needed to
start the program, which is the minimum number for any run.
Then, as superuser, and in a separate window, run _s_q_u_e_e_z_e to lock down
varying amounts of memory, and rerun ``ssusage thrash -m 4". The major-
fault number will remain low at first, but as you squeeze out more and
more memory, it will rise. The amount of available memory reported by
_s_q_u_e_e_z_e at point at which _t_h_r_a_s_h begins to page-fault tells you the
combined working set of _t_h_r_a_s_h (~ 4MB), the kernel, and any other
applications you have running.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
ssusage(1), squeeze(1)
PPPPaaaaggggeeee 1111