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Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request

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  Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for  ZONE_MOVABLE request Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2017-08-28 02:30 +0200
    Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for  ZONE_MOVABLE request Vlastimil Babka <vbabka@suse.cz> - 2017-08-28 08:50 +0200
      Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for  ZONE_MOVABLE request Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2017-08-29 02:40 +0200
        Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for  ZONE_MOVABLE request Vlastimil Babka <vbabka@suse.cz> - 2017-08-29 09:10 +0200

#1720953 — Re: [PATCH] mm/page_alloc: don't reserve ZONE_HIGHMEM for ZONE_MOVABLE request

On Fri, Aug 25, 2017 at 09:56:10AM +0200, Vlastimil Babka wrote:
> On 08/25/2017 02:20 AM, Joonsoo Kim wrote:
> > On Thu, Aug 24, 2017 at 11:41:58AM +0200, Vlastimil Babka wrote:
> > 
> > Hmm, this is already pointed by Minchan and I have answered that.
> > 
> > lkml.kernel.org/r/<20170421013243.GA13966@js1304-desktop>
> > 
> > If you have a better idea, please let me know.
> 
> My idea is that size of sysctl_lowmem_reserve_ratio is ZONE_NORMAL+1 and
> it has no entries for zones > NORMAL. The
> setup_per_zone_lowmem_reserve() is adjusted to only set
> lower_zone->lowmem_reserve[j] for idx <= ZONE_NORMAL.
> 
> I can't imagine somebody would want override the ratio for HIGHMEM or
> MOVABLE
> (where it has no effect anyway) so the simplest thing is not to expose
> it at all.

Seems reasonable. However, if there is a user who checks
sysctl_lowmem_reserve_ratio entry for HIGHMEM and change it, suggested
interface will cause a problem since it doesn't expose ratio for
HIGHMEM. Am I missing something?

Thanks.


> 
> > Thanks.
> > 
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

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#1721054

+CC linux-api

On 08/28/2017 02:28 AM, Joonsoo Kim wrote:
> On Fri, Aug 25, 2017 at 09:56:10AM +0200, Vlastimil Babka wrote:
>> On 08/25/2017 02:20 AM, Joonsoo Kim wrote:
>>> On Thu, Aug 24, 2017 at 11:41:58AM +0200, Vlastimil Babka wrote:
>>>
>>> Hmm, this is already pointed by Minchan and I have answered that.
>>>
>>> lkml.kernel.org/r/<20170421013243.GA13966@js1304-desktop>
>>>
>>> If you have a better idea, please let me know.
>>
>> My idea is that size of sysctl_lowmem_reserve_ratio is ZONE_NORMAL+1 and
>> it has no entries for zones > NORMAL. The
>> setup_per_zone_lowmem_reserve() is adjusted to only set
>> lower_zone->lowmem_reserve[j] for idx <= ZONE_NORMAL.
>>
>> I can't imagine somebody would want override the ratio for HIGHMEM or
>> MOVABLE
>> (where it has no effect anyway) so the simplest thing is not to expose
>> it at all.
> 
> Seems reasonable. However, if there is a user who checks
> sysctl_lowmem_reserve_ratio entry for HIGHMEM and change it, suggested
> interface will cause a problem since it doesn't expose ratio for
> HIGHMEM. Am I missing something?

As you explained, it makes little sense to change it for HIGHMEM which
only affects MOVABLE allocations. Also I doubt there are many systems
with both HIGHMEM (implies 32bit) *and* MOVABLE (implies NUMA, memory
hotplug...) zones. So I would just remove it, and if somebody will
really miss it, we can always add it back. In any case, please CC
linux-api on the next version.

> Thanks.
> 
> 
>>
>>> Thanks.
>>>
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org.  For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

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#1722085

On Mon, Aug 28, 2017 at 08:45:07AM +0200, Vlastimil Babka wrote:
> +CC linux-api
> 
> On 08/28/2017 02:28 AM, Joonsoo Kim wrote:
> > On Fri, Aug 25, 2017 at 09:56:10AM +0200, Vlastimil Babka wrote:
> >> On 08/25/2017 02:20 AM, Joonsoo Kim wrote:
> >>> On Thu, Aug 24, 2017 at 11:41:58AM +0200, Vlastimil Babka wrote:
> >>>
> >>> Hmm, this is already pointed by Minchan and I have answered that.
> >>>
> >>> lkml.kernel.org/r/<20170421013243.GA13966@js1304-desktop>
> >>>
> >>> If you have a better idea, please let me know.
> >>
> >> My idea is that size of sysctl_lowmem_reserve_ratio is ZONE_NORMAL+1 and
> >> it has no entries for zones > NORMAL. The
> >> setup_per_zone_lowmem_reserve() is adjusted to only set
> >> lower_zone->lowmem_reserve[j] for idx <= ZONE_NORMAL.
> >>
> >> I can't imagine somebody would want override the ratio for HIGHMEM or
> >> MOVABLE
> >> (where it has no effect anyway) so the simplest thing is not to expose
> >> it at all.
> > 
> > Seems reasonable. However, if there is a user who checks
> > sysctl_lowmem_reserve_ratio entry for HIGHMEM and change it, suggested
> > interface will cause a problem since it doesn't expose ratio for
> > HIGHMEM. Am I missing something?
> 
> As you explained, it makes little sense to change it for HIGHMEM which
> only affects MOVABLE allocations. Also I doubt there are many systems
> with both HIGHMEM (implies 32bit) *and* MOVABLE (implies NUMA, memory
> hotplug...) zones. So I would just remove it, and if somebody will
> really miss it, we can always add it back. In any case, please CC
> linux-api on the next version.

If we will accept a change that potentially breaks the user, I think
that making zero as a special value for sysctl_lowmem_reserve_ratio
is better solution. How about this way?

Thanks.

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#1722191

On 08/29/2017 02:36 AM, Joonsoo Kim wrote:
> On Mon, Aug 28, 2017 at 08:45:07AM +0200, Vlastimil Babka wrote:
>> +CC linux-api
>>
>> On 08/28/2017 02:28 AM, Joonsoo Kim wrote:
>>> On Fri, Aug 25, 2017 at 09:56:10AM +0200, Vlastimil Babka wrote:
>>>
>>> Seems reasonable. However, if there is a user who checks
>>> sysctl_lowmem_reserve_ratio entry for HIGHMEM and change it, suggested
>>> interface will cause a problem since it doesn't expose ratio for
>>> HIGHMEM. Am I missing something?
>>
>> As you explained, it makes little sense to change it for HIGHMEM which
>> only affects MOVABLE allocations. Also I doubt there are many systems
>> with both HIGHMEM (implies 32bit) *and* MOVABLE (implies NUMA, memory
>> hotplug...) zones. So I would just remove it, and if somebody will
>> really miss it, we can always add it back. In any case, please CC
>> linux-api on the next version.
> 
> If we will accept a change that potentially breaks the user, I think
> that making zero as a special value for sysctl_lowmem_reserve_ratio
> is better solution. How about this way?

I'd prefer removal, but won't object to zero. Certainly much better than
UINT_MAX.

> Thanks.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-api" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

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