lib/test_vmalloc: switch to prandom_u32()

A get_random_bytes() function can cause a high contention if it is called
across CPUs simultaneously.  Because it shares one lock per all CPUs:

<snip>
   class name     con-bounces  contentions   waittime-min   waittime-max waittime-total   waittime-avg    acq-bounces   acquisitions   holdtime-min   holdtime-max holdtime-total   holdtime-avg
   &crng->lock:   663145       665886        0.05           8.85         261966.66        0.39            7188152       13731279       0.04           11.89        2181582.30       0.16
   -----------
   &crng->lock    307835       [<00000000acba59cd>] _extract_crng+0x48/0x90
   &crng->lock    358051       [<00000000f0075abc>] _crng_backtrack_protect+0x32/0x90
   -----------
   &crng->lock    234241       [<00000000f0075abc>] _crng_backtrack_protect+0x32/0x90
   &crng->lock    431645       [<00000000acba59cd>] _extract_crng+0x48/0x90
<snip>

Switch from the get_random_bytes() to prandom_u32() that does not have any
internal contention when a random value is needed for the tests.

The reason is to minimize CPU cycles introduced by the test-suite itself
from the vmalloc performance metrics.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: Oleksiy Avramchenko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions