[Devel] Re: [PATCH 02/11] memcg: Reclaim when more than one page needed.

[Glauber Costa]

On 06/27/2012 11:48 PM, David Rientjes wrote:
> On Wed, 27 Jun 2012, Glauber Costa wrote:
> 
>>> @@ -2206,7 +2214,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup
>>> *memcg, gfp_t gfp_mask,
>>>>  	 * unlikely to succeed so close to the limit, and we fall back
>>>>  	 * to regular pages anyway in case of failure.
>>>>  	 */
>>>> -	if (nr_pages == 1 && ret)
>>>> +	if (nr_pages <= NR_PAGES_TO_RETRY && ret)
>>>>  		return CHARGE_RETRY;
>>
>> Changed to costly order.
>>
> 
> 1 << PAGE_ALLOC_COSTLY_ORDER was the suggestion.

That is what I meant - to the costly order suggestion - , should have
been more explicit.

>> One more thing. The original version of this patch included
>> a cond_resched() here, that was also removed. From my re-reading
>> of the code in page_alloc.c and vmscan.c now, I tend to think
>> this is indeed not needed, since any cond_resched()s that might
>> be needed to ensure the safety of the code will be properly
>> inserted by the reclaim code itself, so there is no need for us
>> to include any when we signal that a retry is needed.
>>
> 
> For __GFP_WAIT, that sounds like a safe guarantee.
>