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Date: Mon, 9 Nov 2009 16:46:21 +0100 From: Andi Kleen <andi@...stfloor.org> To: Arnd Bergmann <arnd@...db.de> Cc: Andi Kleen <andi@...stfloor.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, Arjan van de Ven <arjan@...radead.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 22/23] sysctl arm: Remove binary sysctl support > 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. > > > in glibc-ports for the support of arm inb/outb. The only other > > > use in older glibc was checking to see if we ran on an SMP kernel. > > > > That older glibc is widely deployed. And it won't go away next year. > > So? Most users of old glibc are also using old kernels, and they How do you know? At least here it's quite common to use new kernels with old user land. > can still use the config option for the compatibility code. > There wouldn't even be a performance penalty over new glibc with > new kernels which already use procfs. When he drops the sysctl(2) API completely the old userland will be unhappy. > > I just think you should have two flavours of emulation layer: > > full and "common sysctls". This can be probably done with the same > > code and some strategic ifdefs. > > If it's just about code size, I totally wouldn't bother. Just put the > emulation code in loadable module and add a 'printk("Warning, %s is > using sysctl %s, wasting %d kb of kernel memory")' to it's module_init > function. That means non modular kernels can't support old userland. -Andi -- ak@...ux.intel.com -- Speaking for myself only. -- 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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