Linux-Fsdevel Archive on lore.kernel.org
help / color / mirror / Atom feed
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 10:55:52 +0200	[thread overview]
Message-ID: <0f042edf-f277-7637-9913-850cbb7bf3a4@csgroup.eu> (raw)
In-Reply-To: <20200903071144.GA19247@lst.de>



Le 03/09/2020 à 09:11, Christoph Hellwig a écrit :
> 
> 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.
> 

With that patch below, throughput is 113.5MB/s (instead of 99.9MB/s).
So a 14% improvement. That's not bad.

Christophe

> 
> ---
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index abd4ffdc8cdebc..1dc99ab158457a 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -726,6 +726,27 @@ static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter)
>   	return written;
>   }
>   
> +static ssize_t read_zero(struct file *file, char __user *buf,
> +			 size_t count, loff_t *ppos)
> +{
> +	size_t cleared = 0;
> +
> +	while (count) {
> +		size_t chunk = min_t(size_t, count, PAGE_SIZE);
> +
> +		if (clear_user(buf + cleared, chunk))
> +			return cleared ? cleared : -EFAULT;
> +		cleared += chunk;
> +		count -= chunk;
> +
> +		if (signal_pending(current))
> +			return cleared ? cleared : -ERESTARTSYS;
> +		cond_resched();
> +	}
> +
> +	return cleared;
> +}
> +
>   static int mmap_zero(struct file *file, struct vm_area_struct *vma)
>   {
>   #ifndef CONFIG_MMU
> @@ -921,6 +942,7 @@ static const struct file_operations zero_fops = {
>   	.llseek		= zero_lseek,
>   	.write		= write_zero,
>   	.read_iter	= read_iter_zero,
> +	.read		= read_zero,
>   	.write_iter	= write_iter_zero,
>   	.mmap		= mmap_zero,
>   	.get_unmapped_area = get_unmapped_area_zero,
> 

  parent reply	other threads:[~2020-09-03  8:56 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
2020-09-03  8:55             ` Christophe Leroy [this message]
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

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=0f042edf-f277-7637-9913-850cbb7bf3a4@csgroup.eu \
    --to=christophe.leroy@csgroup.eu \
    --cc=hch@lst.de \
    --cc=keescook@chromium.org \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linuxppc-dev@lists.ozlabs.org \
    --cc=mpe@ellerman.id.au \
    --cc=torvalds@linux-foundation.org \
    --cc=viro@zeniv.linux.org.uk \
    --cc=x86@kernel.org \
    --subject='Re: [PATCH 10/10] powerpc: remove address space overrides using set_fs()' \
    /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

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).