Date: Fri, 16 Oct 1998 12:48:29 +0100 (MET) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: Etienne.Debruin@KryptoKom.DE (Etienne de Bruin) Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: timing a device driver Message-ID: <199810161148.MAA00773@labinfo.iet.unipi.it> In-Reply-To: <199810161022.MAA00614@borg.kryptokom.de> from "Etienne de Bruin" at Oct 16, 98 12:22:04 pm
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> i would like to time my device driver from within the kernel.
> so, what functions exist for me to be able to time, in miliseconds,
> how long a chunk of code takes.
a method that i find nice and cheap if you have a pentium is to use the
CPU cycle counter, accessible as follows:
u_long ticks_used, event_count;
...
quad_t ticks;
ticks = rdtsc();
... interesting code ...
ticks_used += (u_long)(rdtsc() - ticks) ;
event_count++;
i generally declare the two variables as SYSCTL variables
SYSCTL_INT(_net_link_ether, OID_AUTO, bdgint, CTLFLAG_RW,
&ticks_used,0,"");
so you can read/set them using sysctl
cheers
luigi
-----------------------------+--------------------------------------
Luigi Rizzo | Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it | Universita' di Pisa
tel: +39-50-568533 | via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522 | http://www.iet.unipi.it/~luigi/
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