Re: Rik van Riel's VM patch

[Rik van Riel <riel@conectiva.com.br>]

On Sun, 3 Sep 2000, Alan Cox wrote:

> > Yes, it kicks butt and it finally (just about) removes the final
> > Linux kernel showstopper for recent kernels. ;-)
> 
> Things like random memory corruption from dropping dirty bits,
> and some of the others are far more serious showstoppers alas

Indeed, there are 4 major issues left in the VM area:

1) system hangs under load with 0 lowmem free (but still
   some high memory free)

   [not much details on this one yet]

2) dirty bits can get lost, try_to_swap_out() and other
   places have a race with the hardware

   [from mm/vmscan.c, line 60 has a race with the /hardware/]
     55         if (pte_young(pte)) {
     56                 /*
     57                  * Transfer the "accessed" bit from the page
     58                  * tables to the global page map.
     59                  */
     60                 set_pte(page_table, pte_mkold(pte));
     61                 SetPageReferenced(page);
     62                 goto out_failed;
     63         }

3) it appears something can corrupt page->count or delete a
   page from the cache while the page is locked

   [tripped up by my VM patch?]

4) the innd data corruption bug

   [anybody?]

regards,

Rik
--
"What you're running that piece of shit Gnome?!?!"
       -- Miguel de Icaza, UKUUG 2000

http://www.conectiva.com/		http://www.surriel.com/

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