linux-kernel - RE: Regression in reading /proc/stat in the newer kernels with large SMP and NUMA configurations

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Fri, 14 Oct 2011 14:48:15 +0100
From:	"Oberman, Laurence (HAS GSE)" <Laurence.Oberman@...com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	"Seger, Mark" <mark.seger@...com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Cabaniols, Sebastien" <Sebastien.Cabaniols@...com>
Subject: RE: Regression in reading /proc/stat in the newer kernels with
 large SMP and NUMA configurations

Hi Eric,
I am preparing for that test. Need to stage a full RHEL6. I had only updated the kernel on an existing SLES10.
Standby and I will run the tests for you.

Thanks
Laurence

-----Original Message-----
From: Eric Dumazet [mailto:eric.dumazet@...il.com] 
Sent: Friday, October 14, 2011 9:47 AM
To: Seger, Mark
Cc: Oberman, Laurence (HAS GSE); linux-kernel@...r.kernel.org; Cabaniols, Sebastien
Subject: RE: Regression in reading /proc/stat in the newer kernels with large SMP and NUMA configurations

Le vendredi 14 octobre 2011 à 14:36 +0100, Seger, Mark a écrit :

> For me the easiest reproducer, which admittedly doesn't show any
> deeper analysis, is to just run "cat /proc/stat>/dev/null" in a loop
> and time it.

OK, but you already provided a global number.

We would like to check where in kernel cpu time is consumed.
Maybe something really obvious could pop out.

"perf" is provided in kernel sources, and really is a piece of cake.

cd tools/perf ; make 

2x4x2 means : Two sockets, 4 cores per physical package, 2 threads per
core.