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Date: Tue, 26 Jul 2005 15:45:44 -0400
From: Florin Malita <fmalita@gmail.com>
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To: cutaway@bellsouth.net
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Subject: Re: kernel 2.6 speed
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cutaway@bellsouth.net wrote:
> Anything time stamping things it processes many of will call some sort of
> time function pretty often.  Could happen frequently with certain classes of
> applications.

Right, but if the timestamp granularity is coarse and there's no 
blocking call in between it makes no sense to invoke 
gettimeofday()/time() repeatedly. I was referring to the kind of app 
that abuses them just because somebody is too lazy to reuse the previous 
value - calling gettimeofday() in 10 sequential printf() statements for eg.

There are legitimate scenarios of course, but this doesn't seem to be 
one of them:

15:22:38.825562 kill(2419, SIGRTMIN)    = 0
15:22:38.825748 gettimeofday({1122405758, 825765}, NULL) = 0
15:22:38.825801 gettimeofday({1122405758, 825812}, NULL) = 0
15:22:38.825845 gettimeofday({1122405758, 825856}, NULL) = 0
15:22:38.825888 gettimeofday({1122405758, 825899}, NULL) = 0
15:22:38.825931 time(NULL)              = 1122405758
15:22:38.825968 gettimeofday({1122405758, 825984}, NULL) = 0
15:22:38.826012 gettimeofday({1122405758, 826022}, NULL) = 0
15:22:38.826062 time(NULL)              = 1122405758
15:22:38.826099 time(NULL)              = 1122405758
15:22:38.826142 time(NULL)              = 1122405758
...

Here's another cute one, just in case you thought calling getpid() once 
should be enough ;)

15:31:15.376157 gettimeofday({1122406275, 376177}, NULL) = 0
15:31:15.376206 getpid()                = 2494
15:31:15.376238 getpid()                = 2494
15:31:15.376264 getpid()                = 2494
15:31:15.376291 getpid()                = 2494
15:31:15.376318 getpid()                = 2494
15:31:15.376344 getpid()                = 2494
15:31:15.376371 getpid()                = 2494
15:31:23.723801 getpid()                = 2494
15:31:23.723845 getpid()                = 2494
15:31:23.723873 getpid()                = 2494
15:31:23.723900 getpid()                = 2494
15:31:23.723927 getpid()                = 2494
15:31:23.723954 getpid()                = 2494
15:31:23.723984 getpid()                = 2494
15:31:23.724011 getpid()                = 2494
15:31:23.724038 getpid()                = 2494
15:31:23.724065 getpid()                = 2494
15:31:23.724091 getpid()                = 2494
15:31:23.724118 getpid()                = 2494
15:31:23.724145 getpid()                = 2494
15:31:23.724171 getpid()                = 2494
15:31:23.724198 getpid()                = 2494
15:31:23.724225 getpid()                = 2494
15:31:24.687109 getpid()                = 2494
15:31:24.687159 getpid()                = 2494
15:31:24.687197 getpid()                = 2494
15:31:24.687247 getpid()                = 2494
15:31:24.687283 getpid()                = 2494
15:31:24.687324 getpid()                = 2494
15:31:24.687364 getpid()                = 2494
15:31:24.687402 getpid()                = 2494
15:31:24.687442 getpid()                = 2494
15:31:24.687477 getpid()                = 2494
15:31:24.687512 getpid()                = 2494
15:31:24.687547 getpid()                = 2494
15:31:24.687583 getpid()                = 2494
15:31:24.687662 semop(32769, 0x430e2e0c, 1) = 0

My point: "real world" apps do stupid things.