Commit c3466952 authored by Johannes Weiner's avatar Johannes Weiner Committed by Peter Zijlstra

psi: Fix a division error in psi poll()

The psi window size is a u64 an can be up to 10 seconds right now,
which exceeds the lower 32 bits of the variable. We currently use
div_u64 for it, which is meant only for 32-bit divisors. The result is
garbage pressure sampling values and even potential div0 crashes.

Use div64_u64.
Signed-off-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarSuren Baghdasaryan <surenb@google.com>
Cc: Jingfeng Xie <xiejingfeng@linux.alibaba.com>
Link: https://lkml.kernel.org/r/20191203183524.41378-3-hannes@cmpxchg.org
parent 3dfbe25c
...@@ -482,7 +482,7 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value) ...@@ -482,7 +482,7 @@ static u64 window_update(struct psi_window *win, u64 now, u64 value)
u32 remaining; u32 remaining;
remaining = win->size - elapsed; remaining = win->size - elapsed;
growth += div_u64(win->prev_growth * remaining, win->size); growth += div64_u64(win->prev_growth * remaining, win->size);
} }
return growth; return growth;
......
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