2.4.0-test9-pre4: __alloc_pages(...) try_again:

[Roger Larsson <roger.larsson@norran.net>]

Hi,


Trying to find out why test9-pre4 freezes with mmap002
I added a counter for try_again loops.

... __alloc_pages(...)

        int direct_reclaim = 0;
        unsigned int gfp_mask = zonelist->gfp_mask;
        struct page * page = NULL;
+       int try_again_loops = 0;

- - -

+         printk("VM: sync kswapd (direct_reclaim: %d) try_again #
%d\n",
+                direct_reclaim, ++try_again_loops);
                        wakeup_kswapd(1);
                        goto try_again;


Result was surprising:
  direct_reclaim was 1.
  try_again_loops did never stop increasing (note: it is not static,
  and should restart from zero after each success)

Why does this happen?
a) kswapd did not succeed in freeing a suitable page?
b) __alloc_pages did not succeed in grabbing the page?

/RogerL

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