[LU-12535] lov_page_index surprisingly slow

• Type: Improvement
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.13.0
• Assignee: Patrick Farrell (Inactive)
• Reporter: Patrick Farrell (Inactive)

Description

When doing readahead, we see an amazing amount of time (~5%) just looking up the page index from the lov layer.

 a
-   84.42%     0.34%  ior              [kernel.kallsyms]     [k] ll_readpage                a
   - 84.08% ll_readpage                                                                     a
      - 82.68% ll_io_read_page                                                              a
         + 68.53% ll_readahead.isra.27                                                      a
         - 14.14% cl_io_submit_rw                                                           a
            - 13.40% lov_io_submit                                                          a
               - 8.24% lov_page_index                                                       a
                    5.56% cl_page_at  

This never changes once a page is created, so we can just store it at the top layer.

Comments

[Peter Jones]

Landed for 2.13

[Gerrit Updater]

Oleg Drokin ([e-mail]) merged in patch https://review.whamcloud.com/35470/
Subject: LU-12535 lov: Move page index to top level
Project: fs/lustre-release
Branch: master
Current Patch Set:
Commit: 8d6d2914cf85be0508805cd5195163e1959652f4

[Patrick Farrell (Inactive)]

I thought this was due to a bug in another patch, but it seems to be, surprisingly, real.  Let's get it fixed...

[Gerrit Updater]

Patrick Farrell ([e-mail]) uploaded a new patch: https://review.whamcloud.com/35470
Subject: LU-12535 lov: Move page index to top level
Project: fs/lustre-release
Branch: master
Current Patch Set: 1
Commit: 17f9a3b0a8163c0adeac0c1e681302e24d84d9f1