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SubjectRe: [PATCH] mm: do not sleep in balance_pgdat if there's no i/o congestion
On 29.12.2012 08:25, Hillf Danton wrote:
> On Thu, Dec 27, 2012 at 11:42 PM, Zlatko Calusic
> <> wrote:
>> On 21.12.2012 12:51, Hillf Danton wrote:
>>> On Thu, Dec 20, 2012 at 7:25 AM, Zlatko Calusic <>
>>> wrote:
>>>> static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
>>>> int
>>>> *classzone_idx)
>>>> {
>>>> - int all_zones_ok;
>>>> + struct zone *unbalanced_zone;
>>> nit: less hunks if not erase that mark
>>> Hillf
>> This one left unanswered and forgotten because I didn't understand what you
>> meant. Could you elaborate?
> Sure, the patch looks simpler(and nicer) if we dont
> erase all_zones_ok.

Ah, yes. I gave it a good thought. But, when I introduced
unbalanced_zone it just didn't make much sense to me to have two
variables with very similar meaning. If I decided to keep all_zones_ok,
it would be either:

all_zones_ok = true
unbalanced_zone = NULL
(meaning: if no zone in unbalanced, then all zones must be ok)


all_zones_ok = false
unbalanced_zone = struct zone *
(meaning: if there's an unbalanced zone, then certainly not all zones
are ok)

So I decided to use only unbalanced_zone (because I had to!), and remove
all_zones_ok to avoid redundancy. I hope it makes sense.

If you check my latest (and still queued) optimization (mm: avoid
calling pgdat_balanced() needlessly), there again popped up a need for a
boolean, but I called it pgdat_is_balanced this time, just to match the
name of two other functions. It could've also been called all_zones_ok
if you prefer the name? Of course, I have no strong feelings about the
name, both are OK, so if you want me to redo the patch, just say.

Generally speaking, while I always attempt to make a smaller patch (less
hunks and less changes = easier to review), before that I'll always try
to make the code that results from the commit cleaner, simpler, more

For example, I'll always check that I don't mess with whitespace
needlessly, unless I think it's actually desirable, here's just one example:

"mm: avoid calling pgdat_balanced() needlessly" changes

} while (--sc.priority >= 0);

if (!pgdat_balanced(pgdat, order, *classzone_idx)) {


} while (--sc.priority >= 0);

if (!pgdat_is_balanced) {

because I find the latter more correct place for the label "out".

Thanks for the comment.

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