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From:   Roman Gushchin <guro@fb.com>
To:     Anshuman Khandual <anshuman.khandual@arm.com>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Kernel Team <Kernel-team@fb.com>,
        "Johannes Weiner" <hannes@cmpxchg.org>,
        Matthew Wilcox <willy@infradead.org>,
        Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH] mm: refactor __vunmap() to avoid duplicated call to
 find_vm_area()
Thread-Topic: [PATCH] mm: refactor __vunmap() to avoid duplicated call to
 find_vm_area()
Thread-Index: AQHVCq//khAEDBlALkSFD6zmmU+RfaZrl42AgADXXoA=
Date:   Wed, 15 May 2019 17:18:05 +0000
Message-ID: <20190515171800.GD9307@castle>
References: <20190514235111.2817276-1-guro@fb.com>
 <78d9b650-4b47-60c5-4212-601c1719dba5@arm.com>
In-Reply-To: <78d9b650-4b47-60c5-4212-601c1719dba5@arm.com>
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On Wed, May 15, 2019 at 09:57:11AM +0530, Anshuman Khandual wrote:
>=20
>=20
> On 05/15/2019 05:21 AM, Roman Gushchin wrote:
> > __vunmap() calls find_vm_area() twice without an obvious reason:
> > first directly to get the area pointer, second indirectly by calling
> > vm_remove_mappings()->remove_vm_area(), which is again searching
> > for the area.
> >=20
> > To remove this redundancy, let's split remove_vm_area() into
> > __remove_vm_area(struct vmap_area *), which performs the actual area
> > removal, and remove_vm_area(const void *addr) wrapper, which can
> > be used everywhere, where it has been used before. Let's pass
> > a pointer to the vm_area instead of vm_struct to vm_remove_mappings(),
> > so it can pass it to __remove_vm_area() and avoid the redundant area
> > lookup.
> >=20
> > On my test setup, I've got 5-10% speed up on vfree()'ing 1000000
> > of 4-pages vmalloc blocks.
>=20
> Though results from  1000000 single page vmalloc blocks remain inconclusi=
ve,
> 4-page based vmalloc block's result shows improvement in the range of 5-1=
0%.

So you can confirm my numbers? Great, thank you!