mpc880 linux-2.6.32 slow running processes

Heiko Schocher <hs@denx.de> wrote on 2011/01/21 07:53:02:
> Hello Joakim,
>
> Joakim Tjernlund wrote:
> >> Sent by: linuxppc-dev-bounces+joakim.tjernlund=transmode.se@lists.ozlabs.org
> >>
> >> Rafael Beims <rbeims@gmail.com> wrote on 2011/01/10 17:35:38:
> >>>> Once you have tested it and it works, please send a patch to remove the 8xx workaround.
> >>>> Make sure Scott is cc:ed
> >>>>
> >>>>
> >>> I tested linux-2.6.33 on my ppc880 board today, and even without the
> >>> slowdown.patch applied, the board runs processes with good
> >>> performance.
> >>> It really seems that the problem is solved from linux-2.6.33 on.
> >>>
> >>> I'm not sure what you mean by sending a patch to remove the
> >>> workaround. The only thing that I did in the 2.6.32 version was to
> >>> apply the slowdown.patch attached in the message from Michael.
> >>>
> >>> Could you clarify please?
> >> Yes, this part in arch/powerpc/mm/pgtable.c:
> >> #ifdef CONFIG_8xx
> >>          /* On 8xx, cache control instructions (particularly
> >>           * "dcbst" from flush_dcache_icache) fault as write
> >>           * operation if there is an unpopulated TLB entry
> >>           * for the address in question. To workaround that,
> >>           * we invalidate the TLB here, thus avoiding dcbst
> >>           * misbehaviour.
> >>           */
> >>          /* 8xx doesn't care about PID, size or ind args */
> >>          _tlbil_va(addr, 0, 0, 0);
> >> #endif /* CONFIG_8xx */
> >>
> >> Should be removed in >= 2.6.33 kernels.
> >> My 8xx TLB work fixes this problem more efficiently.
> >
> > Can you test these 2 patches on recent 2.6 linux:
> >>From 9024200169bf86b4f34cb3b1ebf68e0056237bc0 Mon Sep 17 00:00:00 2001
> > From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
> > Date: Tue, 11 Jan 2011 13:43:42 +0100
> > Subject: [PATCH 1/2] powerpc: Move 8xx invalidation of non present TLBs
> [...]
> > and
> >
> >>From 0ef93601290a75b087495dddeee6062a870f1dc6 Mon Sep 17 00:00:00 2001
> > From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
> > Date: Tue, 11 Jan 2011 13:55:22 +0100
> > Subject: [PATCH 2/2] powerpc: Remove 8xx redundant dcbst workaround.
>
> Tested this on a board similliar to the mainline tqm8xx board with
> lmbench:
>
> -bash-3.2# cat /proc/cpuinfo
> processor       : 0
> cpu             : 8xx
> clock           : 80.000000MHz
> revision        : 0.0 (pvr 0050 0000)
> bogomips        : 10.00
> timebase        : 5000000
> platform        : KUP4K
> model           : KUP4K
> Memory          : 96 MB
> -bash-3.2#
>
> -bash-3.2# cat /proc/version
> Linux version 2.6.34-00064-g3e81b6b (hs@pollux.denx.de) (gcc version 4.2.2) #89 Thu Jan 20 08:39:52 CET 2011
> -bash-3.2#
>
> (First run of lmbench without your 2 patches, the two other runs with it)

Thanks,

From a quick look, the only thing that really stands out is Prot Fault below:

> File & VM system latencies in microseconds - smaller is better
> -------------------------------------------------------------------------------
> Host                 OS   0K File      10K File     Mmap    Prot   Page   100fd
>                         Create Delete Create Delete Latency Fault  Fault  selct
> --------- ------------- ------ ------ ------ ------ ------- ----- ------- -----
> kup4k     Linux 2.6.34-  16.7K  10.3K  90.9K  13.7K   22.6K  27.1    43.4 117.9
> kup4k     Linux 2.6.34-  16.9K  15.6K 100.0K  16.1K   22.7K 9.590    39.8 119.2
> kup4k     Linux 2.6.34-  16.7K  13.5K 100.0K  15.9K   22.8K 9.306    39.8 119.6

Anyhow, nothing broke so I am happy with the results.

On top of those 2 patches I came up with this cleanup patch too:

From 920c236b290ee00d84506369e3898126c78215e8 Mon Sep 17 00:00:00 2001
From: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Date: Tue, 18 Jan 2011 09:50:09 +0100
Subject: [PATCH 3/3] powerpc: Use symbolic constants in 8xx TLB asm

Use the PTE #defines where possible instead of
hardcoded constants.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
---
 arch/powerpc/kernel/head_8xx.S |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

--
1.7.3.4