From: Andrew Morton <akpm@linux-foundation.org>
To: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>, Shaohua Li <shli@fb.com>,
linux-mm@kvack.org, linux-kernel <linux-kernel@vger.kernel.org>,
kernel-team@fb.com
Subject: Re: [PATCH] proc: revert /proc/<pid>/maps [stack:TID] annotation
Date: Tue, 19 Jan 2016 21:27:45 -0800 [thread overview]
Message-ID: <20160119212745.eee310f5.akpm@linux-foundation.org> (raw)
In-Reply-To: <CAAHN_R2CFYsSSU_Qr-_cE+9-=OqDOa88annh9uA1TymuJncL8A@mail.gmail.com>
On Wed, 20 Jan 2016 08:47:39 +0530 Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com> wrote:
> On 20 January 2016 at 03:44, Andrew Morton <akpm@linux-foundation.org> wrote:
> > Any thoughts on the obvious back-compatibility concerns? ie, why did
> > Siddhesh implement this in the first place? My bad for not ensuring
> > that the changelog told us this.
> >
> > https://lkml.org/lkml/2012/1/14/25 has more info:
> >
> > : Memory mmaped by glibc for a thread stack currently shows up as a
> > : simple anonymous map, which makes it difficult to differentiate between
> > : memory usage of the thread on stack and other dynamic allocation.
> > : Since glibc already uses MAP_STACK to request this mapping, the
> > : attached patch uses this flag to add additional VM_STACK_FLAGS to the
> > : resulting vma so that the mapping is treated as a stack and not any
> > : regular anonymous mapping. Also, one may use vm_flags to decide if a
> > : vma is a stack.
> >
> > But even that doesn't really tell us what the actual *value* of the
> > patch is to end-users.
>
> The end users needed a way to identify thread stacks programmatically
> and there wasn't a way to do that. I'm afraid I no longer remember
> (or have access to the resources that would aid my memory since I
> changed employers) the details of their requirement. However, I did
> do this on my own time because I thought it was an interesting project
> for me and nobody really gave any feedback then as to its utility, so
> as far as I am concerned you could roll back the main thread maps
> information since the information is available in the thread-specific
> files.
OK, thanks. I was thinking of queueing this for 4.6 to let it bake in
-next for a cycle, but quadratic performance is bad and nobody will
test such an obscure feature in -next so maybe I'll jam it into 4.5 and we
wait and see.
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next prev parent reply other threads:[~2016-01-20 5:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-19 18:02 [PATCH] proc: revert /proc/<pid>/maps [stack:TID] annotation Johannes Weiner
2016-01-19 22:14 ` Andrew Morton
2016-01-19 23:30 ` Kirill A. Shutemov
2016-01-20 3:21 ` Siddhesh Poyarekar
2016-01-19 23:38 ` Johannes Weiner
2016-01-20 3:17 ` Siddhesh Poyarekar
2016-01-20 5:27 ` Andrew Morton [this message]
2016-01-21 10:49 ` [PATCH] proc: add missing 'mm' variable in nommu is_stack() Arnd Bergmann
-- strict thread matches above, loose matches on Subject: below --
2016-01-25 21:30 [PATCH] proc: revert /proc/<pid>/maps [stack:TID] annotation Colin Cross
2016-01-25 23:14 ` Kirill A. Shutemov
2016-01-25 23:53 ` Colin Cross
2016-01-28 10:25 ` Kirill A. Shutemov
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