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SubjectRe: [PATCH] mm/vmscan: restore zone_reclaim_mode ABI
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On 6/29/20 4:30 PM, Baoquan He wrote:
>> The only way I can plausibly think of "cleaning up" the RECLAIM_ZONE bit
>> would be to raise our confidence that it is truly unused. That takes
>> time, and probably a warning if we see it being set. If we don't run
>> into anybody setting it or depending on it being set in a few years, we
>> can remove it.
> So adding the old bit back for compatibility looks good, thanks.
>
> Then we have to be very careful when adding and reviewing new
> interface introducing, should not leave one which might be used
> in the future.
>
> In fact, RECLAIM_ZONE is not completely useless. At least, when the old
> bit 0 is set, it may enter into node_reclaim() in get_page_from_freelist(),
> that makes it like a switch.
>
> get_page_from_freelist {
>
> ...
> if (node_reclaim_mode == 0 ||
> !zone_allows_reclaim(ac->preferred_zoneref->zone, zone))
> continue;
> ...
> }

Oh, that's a very good point. There are a couple of those around. Let
me circle back and update the documentation and the variable name. I'll
send out another version.

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