From: Marcelo Tosatti <marcelo.tosatti@cyclades•com>
To: Dan Malek <dan@embeddededge•com>
Cc: "Smith, Craig" <craig.d.smith@siemens•com>,
paulus@samba•org,
linux-ppc-embedded <linuxppc-embedded@ozlabs•org>
Subject: Re: Linux 2.6.x on 8xx status
Date: Wed, 23 Mar 2005 07:25:01 -0300 [thread overview]
Message-ID: <20050323102501.GF7846@logos.cnet> (raw)
In-Reply-To: <ab78e7b7625e4293bf29fded17f589c2@embeddededge.com>
On Tue, Mar 22, 2005 at 05:53:40PM -0500, Dan Malek wrote:
>
> On Mar 22, 2005, at 12:58 PM, Marcelo Tosatti wrote:
>
> >Newbie question: What prevents the initial kernel map (tuple of 8Mbyte
> >I/D-TLB entries)
> >and the IMMR 8Mbyte D-TLB entry from getting unmapped by translation
> >pressure,
> >in case CONFIG_PIN_TLB is disabled ?
>
> Nothing. In fact, they are likely invalidated shortly after the kernel
> page tables are set up. This was only done to ensure we could get the
> kernel initialized without taking page faults.
OK.
> >By a counter at the end of _tlbie function, similar to other counters
> >which
> >you suggested.
>
> OK.
>
> >Dont think thats the case given that v2.4 calls tlbia through
> >flush_tlb_mm() at exit_mmap()
> >only. And at vmalloc_free which shouldnt be called at all.
>
> Hmmm ... Then, the 2.6 looks to be much less efficient with the MMU
> resources than 2.4 was. This is going to affect everyone, it's just
> easier
> to measure on this processor.
Many codepaths are longer (eg. but the difference
>
> >I just noticed this conditional at switch_mm() (v2.6), which _can_
> >partly
> >explain the reduced tlbie's (its just a guess for now, though):
>
> What is your guess? I don't know how this would reduce the number
> of tlbie instructions, since stealing a context (as part of
> get_context())
> will simply whack the whole TLB with a tlbia. On 8xx, both instructions
> could be simply implemented as macros.
You misunderstood: get_mmu_context() _wont_ be called if the mm structures
are the same.
v2.4 didnt had this optimization.
> >Spent part of the day reading the MMU section of 860 manual, I think I
> >have kind
> >of a clue how things are supposed to work at the lowlevel now.
>
> :-)
>
> >PS: I can't reproduce the invalid TLB crash anymore. i.e. even by
> >removing
> >the _tlbie() at update_mmu_cache() everything is working as expected.
>
> Well, that's interesting. It's likely to only happen on an 860 variant
> that
> has the large TLB.
For what reasoning?
> >How can I reproduce it again? Guillaume, what kernel version are you
> >using?
>
> It used to happen on early 2.6 versions as soon as you entered user
> space programs.
Will let you know of any findings...
next prev parent reply other threads:[~2005-03-23 15:19 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-21 11:59 Linux 2.6.x on 8xx status Smith, Craig
2004-09-21 11:53 ` Pantelis Antoniou
2004-09-21 16:54 ` Dan Malek
2004-09-21 17:03 ` Dan Malek
2004-09-22 11:09 ` Sam Song
2004-10-15 15:49 ` Marcelo Tosatti
2004-10-16 2:13 ` Marcelo Tosatti
2004-10-16 9:08 ` Sam Song
2004-10-18 5:59 ` Pantelis Antoniou
2004-10-18 6:22 ` Sam Song
2004-10-18 3:10 ` Dan Malek
2005-02-10 15:04 ` Marcelo Tosatti
2005-02-10 19:26 ` Dan Malek
2005-02-10 17:06 ` Marcelo Tosatti
2005-02-10 17:08 ` Marcelo Tosatti
2005-03-21 21:45 ` Guillaume Autran
2005-03-21 21:53 ` Robert P. J. Day
2005-03-22 13:04 ` Marcelo Tosatti
2005-03-22 20:57 ` Dan Malek
2005-03-22 17:58 ` Marcelo Tosatti
2005-03-22 22:53 ` Dan Malek
2005-03-23 10:25 ` Marcelo Tosatti [this message]
2005-03-23 16:12 ` Dan Malek
2005-03-23 16:05 ` Marcelo Tosatti
2005-03-24 14:05 ` Pantelis Antoniou
2005-03-23 14:06 ` Guillaume Autran
2005-02-11 3:42 ` Dan Malek
2005-02-21 21:12 ` Armin Schindler
2005-02-21 23:45 ` Guillaume Autran
2005-02-15 9:39 ` Reading of RTC robin
-- strict thread matches above, loose matches on Subject: below --
2005-02-22 11:20 Linux 2.6.x on 8xx status Joakim Tjernlund
2004-10-25 15:00 Sam Song
2004-09-17 13:57 Smith, Craig
2004-09-17 13:50 ` Pantelis Antoniou
[not found] <20040916201505.E723B2BDB2@ozlabs.org>
2004-09-17 10:06 ` Song Sam
2004-09-17 9:55 ` Pantelis Antoniou
2004-09-18 20:11 ` Song Sam
2004-09-20 6:02 ` Pantelis Antoniou
2004-09-20 11:47 ` Song Sam
2004-09-20 17:49 ` Tom Rini
2004-09-20 18:02 ` Robert P. J. Day
2004-09-20 18:17 ` Tom Rini
2004-09-21 1:38 ` Song Sam
2004-09-21 6:12 ` Pantelis Antoniou
2004-09-21 10:35 ` Song Sam
2004-09-21 10:41 ` Pantelis Antoniou
2004-10-15 15:47 ` Marcelo Tosatti
2004-09-16 18:56 Smith, Craig
2004-09-16 20:07 ` Dan Malek
2004-09-17 5:43 ` Pantelis Antoniou
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