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From: Denys Vlasenko <vda.linux@googlemail.com>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [patch 7/8] Immediate Values - Documentation
Date: Thu, 20 Sep 2007 11:46:57 +0100	[thread overview]
Message-ID: <200709201146.57334.vda.linux@googlemail.com> (raw)
In-Reply-To: <20070827160214.252315593@polymtl.ca>

On Monday 27 August 2007 16:59, Mathieu Desnoyers wrote:
> +We can therefore affirm that adding 2 markers to getppid, on a system with high
> +memory pressure, would have a performance hit of at least 6.0% on the system
> +call time, all within the uncertainty limits of these tests. The same applies to
> +other kernel code paths. The smaller those code paths are, the highest the
> +impact ratio will be.

Immediates make code bigger, right?
What will happen on a system with high *icache* pressure?
There a lot of inline happy and/or C++ folks out there
in the userland, they routinely have programs in tens of megabytes range.

getppid is one of the lightest syscalls out there.
What kind of speedup do you see on a real-world test
(two processes exchaging data through pipes, for example)?

> +Therefore, not only is it interesting to use the immediate values to dynamically
> +activate dormant code such as the markers, but I think it should also be
> +considered as a replacement for many of the "read mostly" static variables.

What effect that will have on "size vmlinux" on AMD64?
--
vda

  reply	other threads:[~2007-09-20 10:47 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-08-27 15:59 [patch 0/8] Immediate Values Mathieu Desnoyers
2007-08-27 15:59 ` [patch 1/8] Immediate Values - Global Modules List and Module Mutex Mathieu Desnoyers
2007-08-27 15:59 ` [patch 2/8] Immediate Values - Architecture Independent Code Mathieu Desnoyers
2007-08-27 15:59 ` [patch 3/8] Immediate Values - Kconfig menu in EMBEDDED Mathieu Desnoyers
2007-08-27 15:59 ` [patch 4/8] Immediate Values - Move Kprobes i386 restore_interrupt to kdebug.h Mathieu Desnoyers
2007-08-27 15:59 ` [patch 5/8] Immediate Values - i386 Optimization Mathieu Desnoyers
2007-08-27 15:59 ` [patch 6/8] Immediate Values - Powerpc Optimization Mathieu Desnoyers
2007-08-27 15:59 ` [patch 7/8] Immediate Values - Documentation Mathieu Desnoyers
2007-09-20 10:46   ` Denys Vlasenko [this message]
2007-09-21 13:31     ` Mathieu Desnoyers
2007-09-21 15:51       ` Denys Vlasenko
2007-08-27 15:59 ` [patch 8/8] Scheduler Profiling - Use Immediate Values Mathieu Desnoyers
  -- strict thread matches above, loose matches on Subject: below --
2007-11-13 18:58 [patch 0/8] Immediate Values (now with merged x86 support) Mathieu Desnoyers
2007-11-13 18:58 ` [patch 7/8] Immediate Values - Documentation Mathieu Desnoyers
2007-08-20 20:23 [patch 0/8] Immediate Values Mathieu Desnoyers
2007-08-20 20:24 ` [patch 7/8] Immediate Values - Documentation Mathieu Desnoyers
2007-08-12 15:07 [patch 0/8] Immediate Values Mathieu Desnoyers
2007-08-12 15:07 ` [patch 7/8] Immediate Values - Documentation Mathieu Desnoyers

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