From: Michael Ellerman <mpe@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Nicholas Piggin <npiggin@gmail.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK
Date: Thu, 24 Jan 2019 12:06:45 +1100 [thread overview]
Message-ID: <87y37ax3ru.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <2e700e1c-5bd9-652e-b535-68a89dd703a1@c-s.fr>
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> Le 12/01/2019 à 10:55, Christophe Leroy a écrit :
>> The purpose of this serie is to activate CONFIG_THREAD_INFO_IN_TASK which
>> moves the thread_info into task_struct.
>>
>> Moving thread_info into task_struct has the following advantages:
>> - It protects thread_info from corruption in the case of stack
>> overflows.
>> - Its address is harder to determine if stack addresses are
>> leaked, making a number of attacks more difficult.
>
> I ran null_syscall and context_switch benchmark selftests and the result
> is surprising. There is slight degradation in context_switch and a
> significant one on null_syscall:
>
> Without the serie:
>
> ~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp
> 55542
> 55562
> 55564
> 55562
> 55568
> ...
>
> ~# ./null_syscall
> 2546.71 ns 336.17 cycles
>
>
> With the serie:
>
> ~# chrt -f 98 ./context_switch --no-altivec --no-vector --no-fp
> 55138
> 55142
> 55152
> 55144
> 55142
>
> ~# ./null_syscall
> 3479.54 ns 459.30 cycles
>
> So 0,8% less context switches per second and 37% more time for one syscall ?
>
> Any idea ?
What platform is that on?
On 64-bit we have to turn one mtmsrd into two and that's obviously a
slow down. But I don't see that you've done anything similar in 32-bit
code.
I assume it's patch 8 that causes the slow down?
cheers
next prev parent reply other threads:[~2019-01-24 1:06 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-12 9:55 [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 01/10] powerpc/irq: use memblock functions returning virtual address Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 02/10] book3s/64: avoid circular header inclusion in mmu-hash.h Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 03/10] powerpc: Only use task_struct 'cpu' field on SMP Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 04/10] powerpc: Prepare for moving thread_info into task_struct Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 05/10] powerpc: Activate CONFIG_THREAD_INFO_IN_TASK Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 06/10] powerpc: regain entire stack space Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 07/10] powerpc: 'current_set' is now a table of task_struct pointers Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 08/10] powerpc/32: Remove CURRENT_THREAD_INFO and rename TI_CPU Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 09/10] powerpc/64: Remove CURRENT_THREAD_INFO Christophe Leroy
2019-01-12 9:55 ` [PATCH v13 10/10] powerpc: clean stack pointers naming Christophe Leroy
2019-01-19 10:23 ` [PATCH v13 00/10] powerpc: Switch to CONFIG_THREAD_INFO_IN_TASK Michael Ellerman
2019-01-19 17:21 ` LEROY Christophe
2019-01-23 23:10 ` Michael Ellerman
2019-01-22 19:42 ` Christophe Leroy
2019-01-24 0:59 ` Michael Ellerman
2019-01-24 15:08 ` Christophe Leroy
2019-01-23 10:04 ` Christophe Leroy
2019-01-24 1:06 ` Michael Ellerman [this message]
2019-01-24 9:43 ` Christophe Leroy
2019-01-24 15:01 ` Christophe Leroy
2019-01-24 15:58 ` Christophe Leroy
2019-01-25 7:00 ` Gabriel Paubert
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87y37ax3ru.fsf@concordia.ellerman.id.au \
--to=mpe@ellerman.id.au \
--cc=benh@kernel.crashing.org \
--cc=christophe.leroy@c-s.fr \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=npiggin@gmail.com \
--cc=paulus@samba.org \
--cc=rppt@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).