linux-kernel - Re: [PATCH v5 4/4] mm/sparse: Optimize memmap allocation during sparse

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Date:   Fri, 29 Jun 2018 11:56:48 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     bhe@...hat.com, LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>, pagupta@...hat.com,
        Linux Memory Management List <linux-mm@...ck.org>,
        kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH v5 4/4] mm/sparse: Optimize memmap allocation during
 sparse_init()

On 06/29/2018 11:01 AM, Pavel Tatashin wrote:
> Correct: it should be incremented on every iteration of the loop. No matter if the entries contained valid data or NULLs. So we increment in three places:
> 
> if map_map[] has invalid entry, increment, continue
> if usemap_map[] has invalid entry, increment, continue
> at the end of the loop, everything was valid we increment it
> 
> This is done so nr_consumed_maps does not get out of sync with the
> current pnum. pnum does not equal to nr_consumed_maps, as there are
> may be holes in pnums, but there is one-to-one correlation.
Can this be made more clear in the code?