Re: [dpdk-dev] [PATCH v3] Fix two compile issues with i686 platform

["Qiu, Michael" <michael.qiu@intel.com>]

On 2014/12/8 19:38, Neil Horman wrote:
> On Mon, Dec 08, 2014 at 03:37:19AM +0000, Qiu, Michael wrote:
>> On 12/8/2014 11:00 AM, Neil Horman wrote:
>>> On Mon, Dec 08, 2014 at 02:46:51AM +0000, Qiu, Michael wrote:
>>>> On 12/5/2014 11:25 PM, Neil Horman wrote:
>>>>> On Fri, Dec 05, 2014 at 03:02:33PM +0000, Bruce Richardson wrote:
>>>>>> On Fri, Dec 05, 2014 at 09:22:05AM -0500, Neil Horman wrote:
>>>>>>> On Fri, Dec 05, 2014 at 04:31:47PM +0800, Chao Zhu wrote:
>>>>>>>> On 2014/12/4 17:12, Michael Qiu wrote:
>>>>>>>>> lib/librte_eal/linuxapp/eal/eal_memory.c:324:4: error: comparison
>>>>>>>>> is always false due to limited range of data type [-Werror=type-limits]
>>>>>>>>>     || (hugepage_sz == RTE_PGSIZE_16G)) {
>>>>>>>>>     ^
>>>>>>>>> cc1: all warnings being treated as errors
>>>>>>>>>
>>>>>>>>> lib/librte_eal/linuxapp/eal/eal.c(461): error #2259: non-pointer
>>>>>>>>> conversion from "long long" to "void *" may lose significant bits
>>>>>>>>>    RTE_PTR_ALIGN_CEIL((uintptr_t)addr, RTE_PGSIZE_16M);
>>>>>>>>>
>>>>>>>>> This was introuduced by commit b77b5639:
>>>>>>>>>         mem: add huge page sizes for IBM Power
>>>>>>>>>
>>>>>>>>> The root cause is that size_t and uintptr_t are 32-bit in i686
>>>>>>>>> platform, but RTE_PGSIZE_16M and RTE_PGSIZE_16G are always 64-bit.
>>>>>>>>>
>>>>>>>>> Define RTE_PGSIZE_16G only in 64 bit platform to avoid
>>>>>>>>> this issue.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Michael Qiu <michael.qiu@intel.com>
>>>>>>>>> ---
>>>>>>>>>  v3 ---> v2
>>>>>>>>> 	Change RTE_PGSIZE_16G from ULL to UL
>>>>>>>>> 	to keep all entries consistent
>>>>>>>>>
>>>>>>>>>  V2 ---> v1
>>>>>>>>> 	Change two type entries to one, and
>>>>>>>>> 	leave RTE_PGSIZE_16G only valid for
>>>>>>>>> 	64-bit platform
>>>>>>>>>
>>>>>>> NACK, this is the wrong way to fix this problem.  Pagesizes are independent of
>>>>>>> architecutre.  While a system can't have a hugepage size that exceeds its
>>>>>>> virtual address limit, theres no need to do per-architecture special casing of
>>>>>>> page sizes here.  Instead of littering the code with ifdef RTE_ARCH_64
>>>>>>> everytime you want to check a page size, just convert the size_t to a uint64_t
>>>>>>> and you can allow all of the enumerated page types on all architecutres, and
>>>>>>> save yourself some ifdeffing in the process.
>>>>>>>
>>>>>>> Neil
>>>>>> While I get your point, I find it distasteful to use a uint64_t for memory sizes,
>>>>>> when there is the size_t type defined for that particular purpose.
>>>>>> However, I suppose that reducing the number of #ifdefs compared to using the
>>>>>> "correct" datatypes for objects is a more practical optino - however distastful
>>>>>> I find it.
>>>>> size_t isn't defined for memory sizes in the sense that we're using them here.
>>>>> size_t is meant to address the need for a type to describe object sizes on a
>>>>> particular system, and it itself is sized accordingly (32 bits on a 32 bit arch,
>>>>> 64 on 64), so that you can safely store a size that the system in question might
>>>>> maximally allocate/return.  In this situation we are describing memory sizes
>>>>> that might occur no a plurality of arches, and so size_t is inappropriate
>>>>> because it as a type is not sized for anything other than the arch it is being
>>>>> built for.  The pragmatic benefits of ennumerating page sizes in a single
>>>>> canonical location far outweigh the desire to use a misappropriated type to
>>>>> describe them.
>>>> Neil,
>>>>
>>>> This patch fix two compile issues, and we need to do *dpdk testing
>>>> affairs*,  if it is blocked in build stage, we can do *nothing* for testing.
>>>>
>>>> I've get you mind and your concern. But we should take care of changing
>>>> the type of "hugepage_sz", because lots of places using it.
>>>>
>>>> Would you mind if we consider this as hot fix, and we can post a better
>>>> fix later(like in dpdk 2.0)? Otherwise all test cycle are blocked.
>>>>
>>> Honestly, no.  Because intels testing schedule shouldn't drive the inclusion of
>>> upstream fixes.  Also, I'm not asking for a major redesign of anything, I'm
>>> asking for a proper fix for a very straightforward problem.  I've attached the
>>> proper fix below.
>>>
>>> Regards
>>> Neil
>> We test dpdk upstream now as 1,8 rc2 and rc3 released :)
>>
> Yes, I don't take issue with you testing dpdk, on the contrary, I appreciate it.
> What I take issue with is that you are asserting that the blockage of your
> testing is reason to ignore a proper fix an issue, rather than some substandard
> one.

Agree :)

>> I know that what you mean. but lots of please using "hugepage_sz" do you
>> confirm it will not affect other issue?
>>
> 5.  There are 5 placees that use hugepage_sz, as the patch below indicates.
> Thats no alot.
>
> Also, I take issue with the assertion that this patch creates no additional
> problems.  I'm sure it creates no additional problems that your patch wouldn't
> also create, arguably less.  If we were really being pragmatic here, I would
> point out that this problem was caused by the fact that support for an entire
> new architecture was integrated during the -rc phase of a release, which seems
> extreemely risky to me, and as such, the most appropriate thing to do would be
> to back support for ppc out until after the 1.8 release when it could be
> properly tested.  Instead we are slamming in hacked up fixes that throw arch
> specific ifdefs througout the code.
>
>> On other hand, we use 32 bit address in 32 bit platform for better
>> performance(some of places also use uintptr_t for address check and
>> alignment).
>>
> This has nothing to do with address bus size.

Actually, it does, this is one of what I'm fixed. But it also introduced
by support Power Arch.

Other places I have not check yet.

Anyway, I will verify your solution, and to see any potential issues.

Thanks
Michael
>> And it should not acceptable in 32 bit platform to use 64-bit platform
>> specification affairs(like RTE_PGSIZE_16G).
>>
> Ok, so add a single arch specific runtime check during hugepage mapping to exit
> on the 16G size use on 32 bit systems.  Thats a fair and reasonable thing to do,
> though I think the hugepage remap is already ifdeffed for 54 bit arches only.
>
> Neil
>
>