linux-kernel - Re: Possible bug in 2.6.34 slub

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Message-ID: <AANLkTilLq-hn59CBcLnOsnT37ZizQR6MrZX6btKPhfpb@mail.gmail.com>
Date:	Tue, 1 Jun 2010 21:17:40 +0200
From:	Giangiacomo Mariotti <gg.mariotti@...il.com>
To:	Bill Davidsen <davidsen@....com>
Cc:	Randy Dunlap <rdunlap@...otime.net>, linux-kernel@...r.kernel.org
Subject: Re: Possible bug in 2.6.34 slub

On Tue, Jun 1, 2010 at 5:22 AM, Bill Davidsen <davidsen@....com> wrote:
> Randy Dunlap wrote:
>>
>> On Tue, 1 Jun 2010 01:39:43 +0200 Giangiacomo Mariotti wrote:
>>
>>> Hi, I've recently noticed this line on the dmesg output(kernel 2.6.34):
>>> [    0.000000] SLUB: Genslabs=14, HWalign=64, Order=0-3, MinObjects=0,
>>> CPUs=16, Nodes=1
>>>
>>> My cpu is an I7 920, so it has 4 cores and there's hyperthreading
>>> enabled, so there are 8 logical cpus. Is this a bug?
>>
>>
>> No, it's just some boot/init time information.
>>
> I would consider it a bug to claim CPUs=xx when xx is something other than
> the number of cores or the number of SMT threads supported by the processor.
> Of course if /proc/cpuinfo shows four siblings per core or something
> exciting, then it's right and you have a CPU you can sell to gizmodo and
> tell them a drunk left on the bar.
>
So....is it a bug or not?

The point is, I guess(didn't actually look at the code), if that's
just the count of MAX number of cpus supported, which is a config time
 define and then the actual count gets refined afterwards by slub
too(because I know that the rest of the kernel knows I've got 4
cores/8 logical cpus) or not. Is that it? If this is not the case(that
is, it's not a static define used as a MAX value), then I can't see
what kind of boot/init time info it is. If it's a boot-time info, it
just means it's a _wrong_ boot-time info.

-- 
Giangiacomo
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