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Date: Tue, 10 Nov 2009 18:31:51 -0800 From: ebiederm@...ssion.com (Eric W. Biederman) To: Andi Kleen <andi@...stfloor.org> Cc: Arnd Bergmann <arnd@...db.de>, Arjan van de Ven <arjan@...radead.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 22/23] sysctl arm: Remove binary sysctl support Andi Kleen <andi@...stfloor.org> writes: >> Can you name one binary sysctl value that gets accessed more >> than a few times during the execution of a vaguely common >> application? We're talking about microseconds for typically >> write-once or read-once settings. > > For example shell scripts tend to execute programs quite a lot. > >> The question is just how many sysctl values you regard as both >> common and performance critical. > > Very little, I suspect in fact it's only one. I just took a second look, attempting to figure out how much startup overhead my sysctl used. I failed because I don't have a user space old enough that it calls sysctl. I had to go back all of the way to glibc-2.4 to find a version of nptl that calls sysctl at startup. glibc-2.5 on i386 uses uname and all other architectures uses either assumes smp is true or false without performing a system call. I don't believe an inuse version of glibc exists that uses sysctl except the ioperm implementation on arm. So I can't see how being a little slower will impact anyone. Eric -- 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/
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