From: Christophe Leroy <christophe.leroy@csgroup.eu>
To: Christoph Hellwig <hch@lst.de>,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Michael Ellerman <mpe@ellerman.id.au>,
the arch/x86 maintainers <x86@kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Kees Cook <keescook@chromium.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 10/10] powerpc: remove address space overrides using set_fs()
Date: Thu, 3 Sep 2020 09:27:04 +0200 [thread overview]
Message-ID: <e6afe576-c3b2-81af-b042-e5930a8fd4c8@csgroup.eu> (raw)
In-Reply-To: <20200903071144.GA19247@lst.de>
Le 03/09/2020 à 09:11, Christoph Hellwig a écrit :
> On Wed, Sep 02, 2020 at 11:02:22AM -0700, Linus Torvalds wrote:
>> I don't see why this change would make any difference.
>
> Me neither, but while looking at a different project I did spot places
> that actually do an access_ok with len 0, that's why I wanted him to
> try.
>
> That being said: Christophe are these number stables? Do you get
> similar numbers with multiple runs?
Yes the numbers are similar with multiple runs and multiple reboots.
>
>> And btw, why do the 32-bit and 64-bit checks even differ? It's not
>> like the extra (single) instruction should even matter. I think the
>> main reason is that the simpler 64-bit case could stay as a macro
>> (because it only uses "addr" and "size" once), but honestly, that
>> "simplification" doesn't help when you then need to have that #ifdef
>> for the 32-bit case and an inline function anyway.
>
> I'll have to leave that to the powerpc folks. The intent was to not
> change the behavior (and I even fucked that up for the the size == 0
> case).
>
>> However, I suspect a bigger reason for the actual performance
>> degradation would be the patch that makes things use "write_iter()"
>> for writing, even when a simpler "write()" exists.
>
> Except that we do not actually have such a patch. For normal user
> writes we only use ->write_iter if ->write is not present. But what
> shows up in the profile is that /dev/zero only has a read_iter op and
> not a normal read. I've added a patch below that implements a normal
> read which might help a tad with this workload, but should not be part
> of a regression.
>
> Also Christophe: can you bisect which patch starts this? Is it really
> this last patch in the series?
5.9-rc2: 91.5MB/s
Patch 1: 74.9MB/s
Patch 2: 97.9MB/s
Patch 3: 97.7MB/s
Patch 4 to 9: 97.9MB/s
Patch 10: 85.3MB/s
Patch 11: 75.4MB/s
See my other mail, when removing CONFIG_STACKPROTECTOR, I get a stable
99.8MB/s throughput.
Christophe
next prev parent reply other threads:[~2020-09-03 7:27 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-27 15:00 remove the last set_fs() in common code, and remove it for x86 and powerpc v2 Christoph Hellwig
2020-08-27 15:00 ` [PATCH 01/10] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-08-27 15:58 ` David Laight
2020-08-29 9:23 ` 'Christoph Hellwig'
[not found] ` <20200901064849.GI4299@shao2-debian>
2020-09-01 7:08 ` [fs] ef30fb3c60: kernel write not supported for file /sys/kernel/softlockup_panic Christoph Hellwig
2020-08-27 15:00 ` [PATCH 02/10] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-08-27 15:00 ` [PATCH 03/10] uaccess: add infrastructure for kernel builds with set_fs() Christoph Hellwig
2020-08-27 15:00 ` [PATCH 04/10] test_bitmap: skip user bitmap tests for !CONFIG_SET_FS Christoph Hellwig
2020-08-27 15:00 ` [PATCH 05/10] lkdtm: disable set_fs-based " Christoph Hellwig
2020-08-27 18:06 ` Linus Torvalds
2020-08-29 9:24 ` Christoph Hellwig
2020-09-01 18:52 ` Kees Cook
2020-09-01 18:57 ` Kees Cook
2020-09-02 8:09 ` Christoph Hellwig
2020-08-27 15:00 ` [PATCH 06/10] x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h Christoph Hellwig
2020-08-27 15:00 ` [PATCH 07/10] x86: make TASK_SIZE_MAX usable from assembly code Christoph Hellwig
2020-08-27 15:00 ` [PATCH 08/10] x86: remove address space overrides using set_fs() Christoph Hellwig
2020-08-27 18:15 ` Linus Torvalds
2020-08-29 9:25 ` Christoph Hellwig
2020-08-27 15:00 ` [PATCH 09/10] powerpc: use non-set_fs based maccess routines Christoph Hellwig
2020-08-27 15:00 ` [PATCH 10/10] powerpc: remove address space overrides using set_fs() Christoph Hellwig
2020-09-02 6:15 ` Christophe Leroy
2020-09-02 12:36 ` Christoph Hellwig
2020-09-02 13:13 ` David Laight
2020-09-02 13:24 ` Christophe Leroy
2020-09-02 13:51 ` David Laight
2020-09-02 14:12 ` Christophe Leroy
2020-09-02 15:02 ` David Laight
2020-09-02 15:17 ` Christophe Leroy
2020-09-02 18:02 ` Linus Torvalds
2020-09-03 7:11 ` Christoph Hellwig
2020-09-03 7:27 ` Christophe Leroy [this message]
2020-09-03 8:55 ` Christophe Leroy
2020-09-03 7:20 ` Christophe Leroy
2020-08-27 15:31 ` remove the last set_fs() in common code, and remove it for x86 and powerpc v2 Christoph Hellwig
2020-09-01 17:13 ` Christophe Leroy
2020-09-01 17:25 ` Al Viro
2020-09-01 17:42 ` Matthew Wilcox
2020-09-01 18:39 ` Christophe Leroy
2020-09-01 19:01 ` Christophe Leroy
2020-09-02 8:10 ` Christoph Hellwig
2020-10-27 9:29 ` [PATCH 02/10] fs: don't allow splice read/write without explicit ops David Howells
2020-10-27 9:51 ` David Howells
2020-10-27 9:54 ` Christoph Hellwig
2020-10-27 10:38 ` David Howells
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