[Lustre-discuss] Facing issues in applying zero copy patch on rhel6.

Tue Apr 8 03:26:55 PDT 2014

Hi Parinay,

Thanks for your help. I went through that link and it partly answers my 
first question.
I can see that the patch in the link you sent is for 
linux-2.6.32-279.14.1.el6(lustre-2.1.4), but this patch is not included 
in upstream released lustre-2.1.4.
So my next two questions still remain unanswered.

Thanks,
Aayush.

On 4/7/2014 8:48 PM, Parinay Kondekar wrote:
>
>
> On 7 April 2014 17:46, aayush agrawal <aayush.agrawal at calsoftinc.com 
> <mailto:aayush.agrawal at calsoftinc.com>> wrote:
>
>     Hi,
>
>     Following are few questions which still remain unanswered:
>
>      1. I am seeing that zero copy patch existed in lustre-2.1.2, In
>         lustre/kernel-patches/patches directory for rhel5. But it has
>         been removed in latest lustre 2.5.0. Is there any specific
>         reason to remove it?
>
> Little searching gave me this - 
> https://jira.hpdd.intel.com/browse/LU-535 / 
> http://review.whamcloud.com/#/c/1142/ .
>
>      1. If I am correct this code gets invoked from following location
>         from obdfilter(correct me if I am wrong):
>          1. lustre/obdfilter/filter_io_26.c line no:367  &
>             nbsp;                                                                                                                                                                    &
>             nbsp;&nb sp; <snip>
>
>                             /* I only set the page to be constant only
>     if it
>                              * is mapped to a contiguous underlying
>     disk block(s).
>                              * It will then make sure the
>     corresponding device
>                              * cache of raid5 will be overwritten by
>     this page.
>                              * - jay */
>                             if ((rw == OBD_BRW_WRITE) &&
>                                 (nblocks == blocks_per_page) &&
>     mapping_cap_page_constant_write(inode->i_mapping))
>     SetPageConstant(page);
>
>                         </snip>
>
>      1. I want to use this zero copy patch in latest lustre 2.5.0(With
>         kernel linux-2.6.32-358.18.1.el6). I could port patch to this
>         latest kernel. But it looks like obdfilter module has been
>         replaced in latest kernel which used to invoke zero copy
>         changes as mentioned in point 2. I think its ofd module with
>         which it got replaced(??). So latest lustre is not able to
>         invoke zero copy changes(for eg: setting/clearing PG_constant
>         etc.). Is there any different patch available for invoking
>         these zero copy changes?
>      2. Can you also suggest which newly added module in lustre-2.5.0
>         would require these changes?
>
>
>     Thanks,
>     Aayush
>
>
>     On 4/7/2014 4:50 PM, aayush agrawal wrote:
>>     Hi,
>>
>>     I got both the errors resolved. Looks like there was some issue
>>     with my lustre build process itself.
>>     So I think along with raid5-zerocopy-rhel6.patch,
>>     raid5-stats-rhel6.patch was the only additional patch required.
>>
>>     Thanks,
>>     Aayush
>>
>>     On 3/24/2014 8:40 PM, aayush agrawal wrote:
>>>     Hi,
>>>
>>>     I wanted to apply zero copy patch on rhel6 so I followed below
>>>     steps:
>>>
>>>      1. Downloaded lustre-2.1.2 and corresponding kernel
>>>         rpm(linux-2.6.32-220.17.1.el6). The OS I am using is CentOS 6.4.
>>>      2. Applied kernel patches from lustre source code to kernel.
>>>      3. Downloaded a zero copy patch for rhel6 from:
>>>         https://github.com/Xyratex/lustre-stable/blob/b_neo_1.4.0/lustre/kernel_patches/patches/raid5-zerocopy-rhel6.patch
>>>      4. Applied this patch to above kernel.
>>>      5. Then I tried to compile this kernel but it gives undefined
>>>         symbol errors for writes_zcopy and PageConstant.
>>>          1. For writes_zcopy I found another patch on the same git
>>>             hub link:
>>>             https://github.com/Xyratex/lustre-stable/blob/b_neo_1.4.0/lustre/kernel_patches/patches/raid5-stats-rhel6.patch.
>>>          2. For PageConstant I couldn't find any patch to rectify
>>>             this error. Even I do not see usage of
>>>             PG_Constant/SetPageConstant etc. in
>>>             raid5-zerocopy-rhel6.patch which I think is essential.
>>>      6. So my questions are:
>>>          1. I think few patches are missing here. As mentioned above
>>>             one of them would be raid5-stats-rhel6.patch please confirm.
>>>          2. if confirmed, still there has to be at least one patch
>>>             missing (to include PageConstant use). Are there any
>>>             other patches to be applied before I apply
>>>             raid5-stats-rhel6.patch and raid5-zerocopy-rhel6.patch.
>>>          3. I am seeing that this zero copy patch existed in
>>>             lustre-2.1.2, In lustre/kernel-patches/patches directory
>>>             for rhel5. But it has been removed in latest lustre
>>>             2.5.0. Is there any specific reason to remove it.
>>>
>>>     Thanks,
>>>     Aayush
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>
>
>
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