From: Ira Weiny <ira.weiny@intel.com>
To: mtk.manpages@gmail.com
Cc: linux-man@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-api@vger.kernel.org, linux-xfs@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org
Subject: Re: [PATCH] man/statx: Add STATX_ATTR_DAX
Date: Mon, 28 Sep 2020 09:42:00 -0700 [thread overview]
Message-ID: <20200928164200.GA459459@iweiny-DESK2.sc.intel.com> (raw)
In-Reply-To: <20200505002016.1085071-1-ira.weiny@intel.com>
On Mon, May 04, 2020 at 05:20:16PM -0700, 'Ira Weiny' wrote:
> From: Ira Weiny <ira.weiny@intel.com>
>
> Linux 5.8 is slated to have STATX_ATTR_DAX support.
>
> https://lore.kernel.org/lkml/20200428002142.404144-4-ira.weiny@intel.com/
> https://lore.kernel.org/lkml/20200504161352.GA13783@magnolia/
>
> Add the text to the statx man page.
>
> Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Have I sent this to the wrong list? Or perhaps I have missed a reply.
I don't see this applied to the man-pages project.[1] But perhaps I am looking
at the wrong place?
Thank you,
Ira
[1] git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
> ---
> man2/statx.2 | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/man2/statx.2 b/man2/statx.2
> index 2e90f07dbdbc..14c4ab78e7bd 100644
> --- a/man2/statx.2
> +++ b/man2/statx.2
> @@ -468,6 +468,30 @@ The file has fs-verity enabled.
> It cannot be written to, and all reads from it will be verified
> against a cryptographic hash that covers the
> entire file (e.g., via a Merkle tree).
> +.TP
> +.BR STATX_ATTR_DAX (since Linux 5.8)
> +The file is in the DAX (cpu direct access) state. DAX state attempts to
> +minimize software cache effects for both I/O and memory mappings of this file.
> +It requires a file system which has been configured to support DAX.
> +.PP
> +DAX generally assumes all accesses are via cpu load / store instructions which
> +can minimize overhead for small accesses, but may adversely affect cpu
> +utilization for large transfers.
> +.PP
> +File I/O is done directly to/from user-space buffers and memory mapped I/O may
> +be performed with direct memory mappings that bypass kernel page cache.
> +.PP
> +While the DAX property tends to result in data being transferred synchronously,
> +it does not give the same guarantees of O_SYNC where data and the necessary
> +metadata are transferred together.
> +.PP
> +A DAX file may support being mapped with the MAP_SYNC flag, which enables a
> +program to use CPU cache flush instructions to persist CPU store operations
> +without an explicit
> +.BR fsync(2).
> +See
> +.BR mmap(2)
> +for more information.
> .SH RETURN VALUE
> On success, zero is returned.
> On error, \-1 is returned, and
> --
> 2.25.1
>
next prev parent reply other threads:[~2020-09-28 16:48 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-05 0:20 [PATCH] man/statx: Add STATX_ATTR_DAX ira.weiny
2020-09-28 16:42 ` Ira Weiny [this message]
2020-09-29 8:38 ` Michael Kerrisk (man-pages)
2020-09-29 20:09 ` Ira Weiny
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