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  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:	Wed, 11 Nov 2009 14:13:13 +0000 (GMT)
From:	"Maciej W. Rozycki" <macro@...ux-mips.org>
To:	Ralf Baechle <ralf@...ux-mips.org>
cc:	Wu Zhangjin <wuzhangjin@...il.com>,
	David Daney <ddaney@...iumnetworks.com>,
	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
	zhangfx@...ote.com, zhouqg@...il.com, rostedt@...dmis.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Nicholas Mc Guire <der.herr@...r.at>,
	Richard Sandiford <rdsandiford@...glemail.com>,
	Patrik Kluba <kpajko79@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michal Simek <monstr@...str.eu>
Subject: Re: [PATCH v7 04/17] tracing: add static function tracer support
 for MIPS

On Wed, 11 Nov 2009, Ralf Baechle wrote:

> 32-bit with -mlong-call:
> 
> 	lui	$25, %hi(foo)
> 	addiu	$25, %lo(foo)
> 	jalr	$25
[...]
> It's time that we get a -G optimization that works for the kernel; it would
> allow to cut down the -mlong-calls calling sequence to just:
> 
> 	lw/ld	$25, offset($gp)
> 	jalr	$25

 Actually this may be no faster than the above.  The load produces its 
result late and the jump needs its data early, so unless a bypass has been 
implemented in the pipeline, it may well stall for the extra cycle (that's 
the reason for the load-delay slot in the original MIPS I ISA after all).

 Of course there is still the benefit of a reduced cache footprint, but 
the extra load may have to evict a cache line and flush the benefit down 
the drain.  I don't mean it's not to be considered, but it's not at all 
immediately obvious it would be a win.

  Maciej
--
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/

Powered by blists - more mailing lists