RE: [PATCH v3 3/5] treewide: use get_random_u32() when possible

David Laight
2022-10-07T09:15:12Z

From: Christophe Leroy
> Sent: 06 October 2022 18:43
...
> But taking into account that sp must remain 16 bytes aligned, would it
> be better to do something like ?
>
> sp -= prandom_u32_max(PAGE_SIZE >> 4) << 4;

That makes me think...
If prandom_u32_max() is passed a (constant) power of 2 it doesn't
need to do the multiply, it can just do a shift right.

Doesn't it also always get a 32bit random value?
So actually get_random_u32() & PAGE_MASK & ~0xf is faster!

When PAGE_SIZE is 4k, PAGE_SIZE >> 4 is 256 so it could use:
get_ramdom_u8() << 4

You also seem to have removed prandom_u32() in favour of
get_random_u32() but have added more prandom_xxxx() functions.

David

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