linux-kernel - Re: [PATCH] mm: don't show nr_indirectly

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Date:   Mon, 30 Apr 2018 17:30:17 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Michal Hocko <mhocko@...nel.org>, Roman Gushchin <guro@...com>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, kernel-team@...com,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] mm: don't show nr_indirectly_reclaimable in /proc/vmstat

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@...e.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.