linux-kernel - Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 20 Feb 2007 21:48:59 +0300
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Josef Sipek <jsipek@....cs.sunysb.edu>
Cc:	bert hubert <bert.hubert@...herlabs.nl>,
	Andi Kleen <andi@...stfloor.org>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: all syscalls initially taking 4usec on a P4? Re: nonblocking UDPv4 recvfrom() taking 4usec @ 3GHz?

On Tue, Feb 20, 2007 at 01:42:42PM -0500, Josef Sipek (jsipek@....cs.sunysb.edu) wrote:
> A better thing would be to use getuid - it turns into just a return with a
> memory dereference). I ran it on my 3.06GHz P4 (HT, but only UP kernel),
> PREEMPT, HZ=1000...
> 
> 3.290196 0.470588 0.402614 0.396078 0.393464 0.396078 0.386928 0.386928 0.386928 0.386928
> 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928
> 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928
> 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928 0.386928

I got following.

delta for syscall: 9112 cycles = 2.977778 us
delta for syscall: 1224 cycles = 0.400000 us
delta for syscall: 1071 cycles = 0.350000 us
delta for syscall: 1054 cycles = 0.344444 us
delta for syscall: 1054 cycles = 0.344444 us

Likely first overhead related to cache population or gamma-ray radiation.
If it happens only one (it does in my test), then everything is ok I
think. Bert, how frequently you get that long recvfrom()?

-- 
	Evgeniy Polyakov
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/