linux-kernel - Re: [PATCH v2 0/3] vmalloc enhancements

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Message-ID: <20190212184724.GA18339@cmpxchg.org>
Date:   Tue, 12 Feb 2019 13:47:24 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Roman Gushchin <guroan@...il.com>
Cc:     linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>,
        kernel-team@...com, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Roman Gushchin <guro@...com>
Subject: Re: [PATCH v2 0/3] vmalloc enhancements

On Tue, Feb 12, 2019 at 09:56:45AM -0800, Roman Gushchin wrote:
> The patchset contains few changes to the vmalloc code, which are
> leading to some performance gains and code simplification.
> 
> Also, it exports a number of pages, used by vmalloc(),
> in /proc/meminfo.
> 
> Patch (1) removes some redundancy on __vunmap().
> Patch (2) separates memory allocation and data initialization
>   in alloc_vmap_area()
> Patch (3) adds vmalloc counter to /proc/meminfo.
> 
> v2->v1:
>   - rebased on top of current mm tree
>   - switch from atomic to percpu vmalloc page counter

I don't understand what prompted this change to percpu counters.

All writers already write vmap_area_lock and vmap_area_list, so it's
not really saving much. The for_each_possible_cpu() for /proc/meminfo
on the other hand is troublesome.