linux-kernel - Re: [RFC 4/4] mm: show number of vmalloc pages in /proc/meminfo

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Message-ID: <20181214184244.GA5196@castle.DHCP.thefacebook.com>
Date:   Fri, 14 Dec 2018 18:42:50 +0000
From:   Roman Gushchin <guro@...com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     Roman Gushchin <guroan@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [RFC 4/4] mm: show number of vmalloc pages in /proc/meminfo

On Fri, Dec 14, 2018 at 10:29:04AM -0800, Matthew Wilcox wrote:
> On Fri, Dec 14, 2018 at 10:07:20AM -0800, Roman Gushchin wrote:
> > Vmalloc() is getting more and more used these days (kernel stacks,
> > bpf and percpu allocator are new top users), and the total %
> > of memory consumed by vmalloc() can be pretty significant
> > and changes dynamically.
> > 
> > /proc/meminfo is the best place to display this information:
> > its top goal is to show top consumers of the memory.
> > 
> > Since the VmallocUsed field in /proc/meminfo is not in use
> > for quite a long time (it has been defined to 0 by the
> > commit a5ad88ce8c7f ("mm: get rid of 'vmalloc_info' from
> > /proc/meminfo")), let's reuse it for showing the actual
> > physical memory consumption of vmalloc().
> 
> Do you see significant contention on nr_vmalloc_pages?  Also, if it's
> just an atomic_long_t, is it worth having an accessor for it?  And if
> it is worth having an accessor for it, then it can be static.

Not really, so I decided that per-cpu counter is an overkill
right now; but we can easily switch over once we'll notice any contention.
Will add static.

> 
> Also, I seem to be missing 3/4.
> 

Hm, https://lkml.org/lkml/2018/12/14/1048 ?

Thanks!