From: Haren Myneni <haren@linux•vnet.ibm.com>
To: Michael Neuling <mikey@neuling•org>
Cc: linuxppc-dev@lists•ozlabs.org, anton@au1•ibm.com, paulus@samba•org
Subject: Re: [PATCH 0/6] powerpc: SMT priority (PPR) save and restore
Date: Thu, 01 Nov 2012 18:20:17 -0700 [thread overview]
Message-ID: <50931FD1.6040905@linux.vnet.ibm.com> (raw)
In-Reply-To: <25370.1351730689@neuling.org>
On 10/31/2012 05:44 PM, Michael Neuling wrote:
> Haren Myneni <haren@linux•vnet.ibm.com> wrote:
>
>> [PATCH 0/6] powerpc: SMT priority (PPR) save and restore
>>
>> On P7 systems, users can define SMT priority levels 2,3 and 4 for
>> processes so that some can run higher priority than the other ones.
>> In the current kernel, the default priority is set to 4 which prohibits
>> processes for using higher priority. Also the kernel boosts the priority to
>> 4 during exceptions without saving the user defined priorities when
>> the task enters the kernel. So we will be loosing the process PPR value
>> and can not be restored it back when the task exits the kernel.
>>
>> This patchset implements saving and restore the user defined PPR value
>> for all tasks.
>>
>> With null_syscall testcase (http://ozlabs.org/~anton/junkcode/null_syscall.c),
>> this feature takes around extra 10 CPU cycles on average for 25 samples.
>
> Haren,
>
> This version doesn't do PPR save/restore over syscall, so is this above
> statement still true? null_syscall shouldn't be effected at all, right?
>
> Mikey
>
Mikey,
Yes this version does not save/ restore for syscall entries. But we set
default priority 3 for each syscall exit - set HMT_MEDIUM_LOW for
normal return, and set 3 in thread.ppr so that this value will be set
for fast return path.
So I was using null_syscall test case to find out the performance
overhead with this patch-set.
Thanks
Haren
>>
>> Haren Myneni (6):
>> powerpc: Move branch instruction from ACCOUNT_CPU_USER_ENTRY to caller
>> powerpc: Define CPU_FTR_HAS_PPR
>> powerpc: Increase exceptions arrays in paca struct to save PPR
>> powerpc: Define ppr in thread_struct
>> powerpc: Macros for saving/restore PPR
>> powerpc: Implement PPR save/restore
>>
>> arch/powerpc/include/asm/cputable.h | 6 ++-
>> arch/powerpc/include/asm/exception-64s.h | 45 ++++++++++++++++++++++++++----
>> arch/powerpc/include/asm/paca.h | 6 ++--
>> arch/powerpc/include/asm/ppc_asm.h | 27 ++++++++++++++++-
>> arch/powerpc/include/asm/processor.h | 6 ++++
>> arch/powerpc/include/asm/reg.h | 1 +
>> arch/powerpc/kernel/asm-offsets.c | 1 +
>> arch/powerpc/kernel/entry_64.S | 6 +++-
>> arch/powerpc/kernel/exceptions-64e.S | 3 +-
>> arch/powerpc/kernel/exceptions-64s.S | 15 +++++----
>> arch/powerpc/kernel/process.c | 2 +
>> 11 files changed, 96 insertions(+), 22 deletions(-)
>>
>>
>>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists•ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
next prev parent reply other threads:[~2012-11-02 1:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-31 6:49 [PATCH 0/6] powerpc: SMT priority (PPR) save and restore Haren Myneni
2012-11-01 0:44 ` Michael Neuling
2012-11-02 1:20 ` Haren Myneni [this message]
-- strict thread matches above, loose matches on Subject: below --
2012-12-07 7:44 Haren Myneni
2012-09-09 11:32 Haren Myneni
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