On Mon, 17 Dec 2012 13:12:35 -0500
Johannes Weiner <han...@cmpxchg.org> wrote:
> Reclaim pressure balance between anon and file pages is calculated
> through a tuple of numerators and a shared denominator.
>
> Exceptional cases that want to force-scan anon or file pages configure
> the numerators and denominator such that one list is preferred, which
> is not necessarily the most obvious way:
>
> fraction[0] = 1;
> fraction[1] = 0;
> denominator = 1;
> goto out;
>
> Make this easier by making the force-scan cases explicit and use the
> fractionals only in case they are calculated from reclaim history.
>
> And bring the variable declarations/definitions in order.
>
> ...
>
> + u64 fraction[2], uninitialized_var(denominator);
Using uninitialized_var() puts Linus into rant mode. Unkindly, IMO:
uninitialized_var() is documentarily useful and reduces bloat. There is
a move afoot to replace it with
int foo = 0; /* gcc */
To avoid getting ranted at we can do
--- a/mm/vmscan.c~mm-vmscan-clean-up-get_scan_count-fix
+++ a/mm/vmscan.c
@@ -1658,7 +1658,8 @@ static void get_scan_count(struct lruvec
unsigned long *nr)
{
struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat;
- u64 fraction[2], uninitialized_var(denominator);
+ u64 fraction[2];
+ u64 denominator = 0;
struct zone *zone = lruvec_zone(lruvec);
unsigned long anon_prio, file_prio;
enum scan_balance scan_balance;
_
Which bloats the text by six bytes, but will force a nice div-by-zero
if we ever hit that can't-happen path.
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