linux-kernel - Re: [PATCH 0/5] mm/vma: make more mmap logic userland testable

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Message-ID: <68dd91e4-b9c3-413c-b284-f43636e7ffba@lucifer.local>
Date: Thu, 5 Dec 2024 07:03:08 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Wei Yang <richard.weiyang@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
        Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] mm/vma: make more mmap logic userland testable

On Wed, Dec 04, 2024 at 11:56:32PM +0000, Wei Yang wrote:
> On Tue, Dec 03, 2024 at 06:05:07PM +0000, Lorenzo Stoakes wrote:
> >This series carries on the work the work started in previous series and
>                         ^^^      ^^^
>
> Duplicated?

Thanks yes, but trivial enough that I'm not sure it's worth a
correction. Will fix if need to respin.

>
> >continued in commit 52956b0d7fb9 ("mm: isolate mmap internal logic to
> >mm/vma.c"), moving the remainder of memory mapping implementation details
> >logic into mm/vma.c allowing the bulk of the mapping logic to be unit
> >tested.
> >
> >It is highly useful to do so, as this means we can both fundamentally test
> >this core logic, and introduce regression tests to ensure any issues
> >previously resolved do not recur.
> >
> >Vitally, this includes the do_brk_flags() function, meaning we have both
> >core means of userland mapping memory now testable.
> >
> >Performance testing was performed after this change given the brk() system
> >call's sensitivity to change, and no performance regression was observed.
>
> May I ask what performance test is done?

mmtests brk1, brk2 (will-it-scale)

You'd not really expect an impact based on relocation of this code, but
with brk it's always worth checking...

>
>
> --
> Wei Yang
> Help you, Help me