Re: [patch 1/4] memcg: use native word to represent dirtyable pages

[Greg Thelen]

Minchan Kim <minchan.kim@xxxxxxxxx> writes:

> On Mon, Nov 8, 2010 at 7:14 AM, Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
>> The memory cgroup dirty info calculation currently uses a signed
>> 64-bit type to represent the amount of dirtyable memory in pages.
>>
>> This can instead be changed to an unsigned word, which will allow the
>> formula to function correctly with up to 160G of LRU pages on a 32-bit
Is is really 160G of LRU pages?  On 32-bit machine we use a 32 bit
unsigned page number.  With a 4KiB page size, I think that maps 16TiB
(1<<(32+12)) bytes.  Or is there some other limit?
>> system, assuming 4k pages. ÂThat should be plenty even when taking
>> racy folding of the per-cpu counters into account.
>>
>> This fixes a compilation error on 32-bit systems as this code tries to
>> do 64-bit division.
>>
>> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
>> Reported-by: Dave Young <hidave.darkstar@xxxxxxxxx>
> Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Reviewed-by: Greg Thelen <gthelen@xxxxxxxxxx>
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