Re: [linuxsh-dev] memory problem

[SUGIOKA T. <su...@it...>]

On Wed, 2002-10-30 at 00:52, SUGIOKA Toshinobu wrote:
> On my SH7750S (200MHz, 128MB) board, user land application
> causes segmentation fault and/or unaligned access randomly when
> very high memory load with swap on.

This is my fault. I'm trying Stuart Menefy's new TLB handling, and
my modification of kernel caused this problem. After reverting all,
there is no problem about this. I'm sorry for incorrect message.

By the way, I applied Stuart's TLB patch to 2.4 branch, but it does not work at all.
Missing some other part ? 

At 12:49 02/10/30 -0500, Paul Mundt <pau...@ti...> wrote:
>This looks like more of a problem of flush_page_to_ram() not doing its
>job. If we look at DaveM's cache/tlb flushing docs, we see the
>following:
>
>  flush_page_to_ram(struct page *page)
>
>        The physical page 'page' is about to be place into the
>        user address space of a process.  If it is possible for
>        stores done recently by the kernel into this physical
>        page, to not be visible to an arbitrary mapping in userspace,
>        you must flush this page from the D-cache.
>
>        If the D-cache is writeback in nature, the dirty data (if
>        any) for this physical page must be written back to main
>        memory before the cache lines are invalidated.
>
>This looks pretty straightforward in nature, and for this application, I
>think we'd be better off simply aliasing flush_page_to_ram() to
>flush_dcache_page(). At least it looks like it'll do the Right Thing(tm)
>more often then not that way (with potentially a few extra dcache
>flushes..).
>

This patch causes extra dcache flushes too much.

before 
   374 __copy_user_page                           4.4524
   480 schedule                                   0.4286
   488 net_send_packet                            1.1731
   592 __clear_user_page                         12.3333
   622 __flush_cache_page                         2.1597
  1227 statm_pgd_range                            2.7388
  1750 pss2001_insw                              13.6719
  5709 cpu_idle                                  35.6812
 26515 total                                      0.0214

after
   212 __flush_cache_page                         0.7361
   223 __copy_user_page                           2.6548
   226 __clear_user_page                          4.7083
   316 do_wp_page                                 0.4938
   614 pss2001_insw                               4.7969
   773 do_anonymous_page                          2.6840
  1058 flush_page_to_ram                          4.1328
  2085 filemap_nopage                             2.9616
  2645 do_no_page                                 7.5142
  2830 cpu_idle                                  17.6875
 16878 total                                      0.0136

Regards.

----
SUGIOKA Toshinobu