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: Tue, 22 Mar 2005 14:58:15 -0300 [thread overview]
Message-ID: <20050322175815.GB7846@logos.cnet> (raw)
In-Reply-To: <f4f476b5e54e9f005dd28082bd5f16fe@embeddededge.com>
On Tue, Mar 22, 2005 at 03:57:08PM -0500, Dan Malek wrote:
>
> On Mar 22, 2005, at 8:04 AM, Marcelo Tosatti wrote:
>
> >I'm quite puzzled. Why v2.6 calls the "tlbie" instruction 100-or-so
> >less times than v2.4 ?
That was rather a _factor_ of "100-or-so" less.
> Oh my ... I'm more worried about the high number of TLB misses
> in 2.6 compared to 2.4. That's really bad.
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 ?
> How did you instrument the tlbie measurement?
By a counter at the end of _tlbie function, similar to other counters which
you suggested.
> It could be that 2.4 used lots more 'tlbia' which were replaced by tlbie in 2.6.
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.
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):
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
#ifdef CONFIG_ALTIVEC
asm volatile (
BEGIN_FTR_SECTION
"dssall;\n"
#ifndef CONFIG_POWER4
"sync;\n" /* G4 needs a sync here, G5 apparently not */
#endif
END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
: : );
#endif /* CONFIG_ALTIVEC */
tsk->thread.pgdir = next->pgd;
/* No need to flush userspace segments if the mm doesnt change */
if (prev == next) <--------------
return; <--------------
/* Setup new userspace context */
get_mmu_context(next);
set_context(next->context, next->pgd);
}
I'm about to disable it and retry.
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.
I'll continue tracking it down - any help is appreciated.
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.
How can I reproduce it again? Guillaume, what kernel version are you using?
next prev parent reply other threads:[~2005-03-22 22:25 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 [this message]
2005-03-22 22:53 ` Dan Malek
2005-03-23 10:25 ` Marcelo Tosatti
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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