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Subject: Re: [PATCH] mm: don't show nr_indirectly_reclaimable in /proc/vmstat
References: <20180425191422.9159-1-guro@fb.com>
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From: Vlastimil Babka <vbabka@suse.cz>
Message-ID: <da797c29-129c-1591-bb85-79817dafd912@suse.cz>
Date: Mon, 30 Apr 2018 17:30:17 +0200
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To: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@kernel.org>, Roman Gushchin <guro@fb.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, kernel-team@fb.com, Matthew Wilcox <willy@infradead.org>, Andrew Morton <akpm@linux-foundation.org>, Alexander Viro <viro@zeniv.linux.org.uk>, Johannes Weiner <hannes@cmpxchg.org>

On 04/27/2018 08:41 PM, David Rientjes wrote:
> On Fri, 27 Apr 2018, Vlastimil Babka wrote:
> 
>> It was in the original thread, see e.g.
>> <08524819-14ef-81d0-fa90-d7af13c6b9d5@suse.cz>
>>
>> However it will take some time to get that in mainline, and meanwhile
>> the current implementation does prevent a DOS. So I doubt it can be
>> fully reverted - as a compromise I just didn't want the counter to
>> become ABI. TBH though, other people at LSF/MM didn't seem concerned
>> that /proc/vmstat is an ABI that we can't change (i.e. counters have
>> been presumably removed in the past already).
>>
> 
> What prevents this from being a simple atomic_t that gets added to in 
> __d_alloc(), subtracted from in __d_free_external_name(), and read in 
> si_mem_available() and __vm_enough_memory()?

The counter is already in mainline, so I think it's easier to simply
just stop printing it now than trying to replace its implementation with
one that can cause cache ping pongs.