From: Andy Lutomirski <luto@amacapital.net>
To: Michal Hocko <mhocko@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>, X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
Borislav Petkov <bp@alien8.de>, Nadav Amit <nadav.amit@gmail.com>,
Kees Cook <keescook@chromium.org>,
Brian Gerst <brgerst@gmail.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Josh Poimboeuf <jpoimboe@redhat.com>, Jann Horn <jann@thejh.net>,
Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [PATCH v2 06/13] fork: Add generic vmalloced stack support
Date: Mon, 20 Jun 2016 09:13:55 -0700 [thread overview]
Message-ID: <CALCETrV3M0a4Xyro21Rz8gpkq1b8PnFUZm_NPnBr0BBO8HS6ug@mail.gmail.com> (raw)
In-Reply-To: <20160620133614.GE9892@dhcp22.suse.cz>
On Mon, Jun 20, 2016 at 6:36 AM, Michal Hocko <mhocko@kernel.org> wrote:
> On Fri 17-06-16 13:00:42, Andy Lutomirski wrote:
>> If CONFIG_VMAP_STACK is selected, kernel stacks are allocated with
>> vmalloc_node.
>
> I like this! It also reduces demand for higher order (order-2) pages
> considerably which is a great plus on its own. I would be little bit
> worried about the performance because vmalloc wasn't the fastest one
> AFAIR. Have you tried to measure that?
It seems to add about 1.5µs to pthread_create+join on my laptop. (On
an unmodified, stripped-down kernel, it took about 7µs before. On a
Fedora system, the baseline is much worse.) I think that most of the
overhead is because vmalloc allocates one page at a time, which means
that it won't use a higher order page even if one is sitting on a
freelist.
I can imagine better integration with the page allocator in which
higher order pages are used if readily available. Similarly, vfree
could free pages that happen to be aligned and consecutive as a unit
to avoid the overhead of merging them back together one at a time.
But I'm not planning on doing any of this myself any time soon. I
just want to get the code working and merged.
--Andy
next prev parent reply other threads:[~2016-06-20 16:13 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-17 20:00 [PATCH v2 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:30 ` Borislav Petkov
2016-06-18 10:29 ` Andy Lutomirski
2016-06-18 10:29 ` Andy Lutomirski
2016-06-18 10:37 ` Borislav Petkov
2016-06-18 10:37 ` Borislav Petkov
2016-06-17 20:00 ` [PATCH v2 04/13] mm: Track NR_KERNEL_STACK in KiB instead of number of stacks Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-20 13:16 ` Michal Hocko
2016-06-20 13:16 ` Michal Hocko
2016-06-17 20:00 ` [PATCH v2 05/13] mm: Move memcg stack accounting to account_kernel_stack Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:55 ` Josh Poimboeuf
2016-06-17 22:18 ` Andy Lutomirski
2016-06-20 13:02 ` Michal Hocko
2016-06-20 13:02 ` Michal Hocko
2016-06-20 16:05 ` Andy Lutomirski
2016-06-20 16:05 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 06/13] fork: Add generic vmalloced stack support Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:57 ` Josh Poimboeuf
2016-06-17 20:57 ` Josh Poimboeuf
2016-06-17 22:18 ` Andy Lutomirski
2016-06-17 22:18 ` Andy Lutomirski
2016-06-20 13:36 ` Michal Hocko
2016-06-20 13:36 ` Michal Hocko
2016-06-20 16:13 ` Andy Lutomirski [this message]
2016-06-20 16:13 ` Andy Lutomirski
2016-06-21 8:46 ` Michal Hocko
2016-06-21 17:01 ` Andy Lutomirski
2016-06-21 17:01 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 12/13] x86/mm/64: Enable vmapped stacks Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
2016-06-17 20:00 ` [PATCH v2 13/13] x86/mm: Improve stack-overflow #PF handling Andy Lutomirski
2016-06-17 20:00 ` Andy Lutomirski
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