From: Pasha Tatashin <pasha.tatashin@soleen.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: David Stevens <stevensd@google.com>,
Pasha Tatashin <pasha.tatashin@soleen.com>,
Linus Walleij <linus.walleij@linaro.org>,
Will Deacon <willdeacon@google.com>,
Quentin Perret <qperret@google.com>,
Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@kernel.org>, Xin Li <xin@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@kernel.org>,
Lorenzo Stoakes <ljs@kernel.org>,
"Liam R. Howlett" <Liam.Howlett@oracle.com>,
Vlastimil Babka <vbabka@kernel.org>,
Mike Rapoport <rppt@kernel.org>,
Suren Baghdasaryan <surenb@google.com>,
Michal Hocko <mhocko@suse.com>,
Uladzislau Rezki <urezki@gmail.com>, Kees Cook <kees@kernel.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 00/13] Dynamic Kernel Stacks
Date: Fri, 24 Apr 2026 21:35:20 +0000 [thread overview]
Message-ID: <aevhw9xqz1pWA2Ow@plex> (raw)
In-Reply-To: <da9321ad-4198-494e-b9fa-30d69bd29be3@intel.com>
On 04-24 12:41, Dave Hansen wrote:
> On 4/24/26 12:14, David Stevens wrote:
> > The question is then: is this approach something that is fundamentally
> > untenable in the kernel
>
> Yes. Fundamentally untenable.
>
> Not allowing stack faults has been a wonderful simplification. It's one
> of those things that just plain makes the kernel easier to maintain.
> Saving low single digits of system memory is not exactly making me eager
> to go back to the harder-to-maintain days.
>
> I seriously doubt that this 1% is the lowest hanging fruit for memory
> bloat on these systems. ;)
This true until, in a fleet of millions of machines, you encounter a
one-in-a-billion chance of a stack overflow. You are then forced to
double the statically allocated kernel stacks on every machine, paying a
memory tax even though 99.999..% of threads never exceed 4K. This
overhead accumulates to petabytes of wasted capacity.
Pasha
next prev parent reply other threads:[~2026-04-24 21:35 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-24 19:14 [PATCH v2 00/13] Dynamic Kernel Stacks David Stevens
2026-04-24 19:14 ` [PATCH v2 01/13] fork: Remove assumption that vm_area->nr_pages equals to THREAD_SIZE David Stevens
2026-04-24 19:14 ` [PATCH v2 02/13] fork: Don't assume fully populated stack during reuse David Stevens
2026-04-24 19:14 ` [PATCH v2 03/13] fork: Move vm_stack to the beginning of the stack David Stevens
2026-04-24 19:14 ` [PATCH v2 04/13] fork: separate vmap stack allocation and free calls David Stevens
2026-04-24 19:14 ` [PATCH v2 05/13] mm/vmalloc: Add a get_vm_area_node() and vmap_pages_range() public functions David Stevens
2026-04-24 19:14 ` [PATCH v2 06/13] fork: Move vmap stack freeing to work queue David Stevens
2026-04-24 19:14 ` [PATCH v2 07/13] fork: Dynamic Kernel Stacks David Stevens
2026-04-24 19:14 ` [PATCH v2 08/13] task_stack.h: Add stack_not_used() support for dynamic stack David Stevens
2026-04-24 19:14 ` [PATCH v2 09/13] fork: Dynamic Kernel Stack accounting David Stevens
2026-04-24 19:14 ` [PATCH v2 10/13] fork: Store task pointer in unpopulated stack ptes David Stevens
2026-04-24 19:14 ` [PATCH v2 11/13] x86/entry/fred: encode frame pointer on entry David Stevens
2026-04-24 19:14 ` [PATCH v2 12/13] x86: Add support for dynamic kernel stacks via FRED David Stevens
2026-04-24 19:14 ` [PATCH v2 13/13] x86: Add support for dynamic kernel stacks via IST David Stevens
2026-04-24 19:41 ` [PATCH v2 00/13] Dynamic Kernel Stacks Dave Hansen
2026-04-24 21:35 ` Pasha Tatashin [this message]
2026-04-24 22:21 ` Dave Hansen
2026-04-24 22:49 ` David Stevens
2026-04-24 22:26 ` David Laight
2026-04-24 23:06 ` Pasha Tatashin
2026-04-25 9:19 ` H. Peter Anvin
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