Re: [RFC 1/3] /dev/low_mem_notify

[Rik van Riel <riel@redhat.com>]

On 01/17/2012 04:27 AM, Pekka Enberg wrote:
> On Tue, Jan 17, 2012 at 10:13 AM, Minchan Kim<minchan@kernel.org>  wrote:
>> +static unsigned int low_mem_notify_poll(struct file *file, poll_table *wait)
>> +{
>> +        unsigned int ret = 0;
>> +
>> +        poll_wait(file,&low_mem_wait, wait);
>> +
>> +        if (atomic_read(&nr_low_mem) != 0) {
>> +                ret = POLLIN;
>> +                atomic_set(&nr_low_mem, 0);
>> +        }
>> +
>> +        return ret;
>> +}
>
> Doesn't this mean that only one application will receive the notification?

One at a time, which could be a good thing since the last
thing we want to do when the system is under memory
pressure is create a thundering herd.

OTOH, we do need to ensure that programs take turns getting
the memory pressure notification.  I do not know whether
poll_wait automatically takes care of that...

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