On 25/06/15 22:18, Daniel Kiper wrote:
> On Thu, Jun 25, 2015 at 06:11:01PM +0100, David Vrabel wrote:
>> Now that we track the total number of pages (included hotplugged
>> regions), it is easy to determine if more memory needs to be
>> hotplugged.
>>
>> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
>> ---
>> drivers/xen/balloon.c | 16 +++++++++++++---
>> 1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
>> index 960ac79..dd41da8 100644
>> --- a/drivers/xen/balloon.c
>> +++ b/drivers/xen/balloon.c
>> @@ -241,12 +241,22 @@ static void release_memory_resource(struct resource *resource)
>> * bit set). Real size of added memory is established at page onlining stage.
>> */
>>
>> -static enum bp_state reserve_additional_memory(long credit)
>> +static enum bp_state reserve_additional_memory(void)
>> {
>> + long credit;
>> struct resource *resource;
>> int nid, rc;
>> unsigned long balloon_hotplug;
>>
>> + credit = balloon_stats.target_pages - balloon_stats.total_pages;
>> +
>> + /*
>> + * Already hotplugged enough pages? Wait for them to be
>> + * onlined.
>> + */
>
> Comment is wrong or at least misleading. Both values does not depend on onlining.
If we get here and credit <=0 then the balloon is empty and we have
already hotplugged enough sections to reach target. We need to wait for
userspace to online the sections that already exist.
>> + if (credit <= 0)
>> + return BP_EAGAIN;
>
> Not BP_EAGAIN for sure. It should be BP_DONE but then balloon_process() will go
> into loop until memory is onlined at least up to balloon_stats.target_pages.
> BP_ECANCELED does work but it is misleading because it is not an error. So, maybe
> we should introduce BP_STOP (or something like that) which works like BP_ECANCELED
> and is not BP_ECANCELED.
We don't want to spin while waiting for userspace to online a new
section so BP_EAGAIN is correct here as it causes the balloon process to
be rescheduled at a later time.
David
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