linux-kernel - Re: [PATCH 2/3] mm: separate memory allocation and actual work in alloc_vmap

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Date:   Wed, 17 Apr 2019 15:27:56 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Roman Gushchin <guro@...com>
Cc:     Roman Gushchin <guroan@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH 2/3] mm: separate memory allocation and actual work in
 alloc_vmap_area()

On 3/1/19 5:48 PM, Roman Gushchin wrote:
> On Fri, Mar 01, 2019 at 03:43:19PM +0100, Vlastimil Babka wrote:
>> On 2/25/19 9:30 PM, Roman Gushchin wrote:
>>> alloc_vmap_area() is allocating memory for the vmap_area, and
>>> performing the actual lookup of the vm area and vmap_area
>>> initialization.
>>>
>>> This prevents us from using a pre-allocated memory for the map_area
>>> structure, which can be used in some cases to minimize the number
>>> of required memory allocations.
>>
>> Hmm, but that doesn't happen here or in the later patch, right? The only
>> caller of init_vmap_area() is alloc_vmap_area(). What am I missing?
> 
> So initially the patch was a part of a bigger patchset, which
> tried to minimize the number of separate allocations during vmalloc(),
> e.g. by inlining vm_struct->pages into vm_struct for small areas.
> 
> I temporarily dropped the rest of the patchset for some rework,
> but decided to leave this patch, because it looks like a nice refactoring
> in any case, and also it has been already reviewed and acked by Matthew
> and Johannes.

OK then,

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> Thank you for looking into it!
>