From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47992AA8.6040804@sgi.com> Date: Thu, 24 Jan 2008 16:17:44 -0800 From: Mike Travis MIME-Version: 1.0 Subject: Re: [PATCH 0/3] percpu: Optimize percpu accesses References: <20080123044924.508382000@sgi.com> <20080124224613.GA24855@elte.hu> In-Reply-To: <20080124224613.GA24855@elte.hu> Content-Type: multipart/mixed; boundary="------------030401050506050503060209" Sender: owner-linux-mm@kvack.org Return-Path: To: Ingo Molnar Cc: Andrew Morton , Andi Kleen , Christoph Lameter , jeremy@goop.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: This is a multi-part message in MIME format. --------------030401050506050503060209 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Ingo Molnar wrote: > * travis@sgi.com wrote: > >> This patchset provides the following: >> >> * Generic: Percpu infrastructure to rebase the per cpu area to zero >> >> This provides for the capability of accessing the percpu variables >> using a local register instead of having to go through a table >> on node 0 to find the cpu-specific offsets. It also would allow >> atomic operations on percpu variables to reduce required locking. >> >> * x86_64: Fold pda into per cpu area >> >> Declare the pda as a per cpu variable. This will move the pda >> area to an address accessible by the x86_64 per cpu macros. >> Subtraction of __per_cpu_start will make the offset based from >> the beginning of the per cpu area. Since %gs is pointing to the >> pda, it will then also point to the per cpu variables and can be >> accessed thusly: >> >> %gs:[&per_cpu_xxxx - __per_cpu_start] >> >> * x86_64: Rebase per cpu variables to zero >> >> Take advantage of the zero-based per cpu area provided above. Then >> we can directly use the x86_32 percpu operations. x86_32 offsets >> %fs by __per_cpu_start. x86_64 has %gs pointing directly to the >> pda and the per cpu area thereby allowing access to the pda with >> the x86_64 pda operations and access to the per cpu variables >> using x86_32 percpu operations. > > tried it on x86.git and 1/3 did not build and 2/3 causes a boot hang > with the attached .config. > > Ingo > The build error was fixed with the note I sent to you yesterday with a "fixup" patch for changes in -mm but not in x86.git (attached). I'll try out your config next. Thanks, Mike --------------030401050506050503060209 Content-Type: text/plain; name="zero-based-x86.git-fix" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="zero-based-x86.git-fix" Subject: x86: fixes conflict between -mm and x86.git Ingo - you can apply this to x86.git after the other zero-based changes to fix a build problem. Thanks, Mike Signed-off-by: Mike Travis --- kernel/module.c | 3 --- 1 file changed, 3 deletions(-) --- a/kernel/module.c +++ b/kernel/module.c @@ -341,9 +341,6 @@ static inline unsigned int block_size(in return val; } -/* Created by linker magic */ -extern char __per_cpu_start[], __per_cpu_end[]; - static void *percpu_modalloc(unsigned long size, unsigned long align, const char *name) { --------------030401050506050503060209-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org