[meta-fsl-arm][PATCH] classes: use dd's option fsync instead of sync

[meta-fsl-arm][PATCH] classes: use dd's option fsync instead of sync

[Stefan Christ]

The shell command sync flushes all filesystem buffers in the system.  On
a bigger multiuser system there are multiple gigs of data sometimes in
the buffer which then are written out to disk at once.  It's better to
only flush the specific file with dd's option 'fsync'.

Signed-off-by: Stefan Christ <s.christ@phytec.de>
---
Hi,

I'm curious why the bbclass image_types_fsl.bbclass uses a double 'sync' to
burn the sdcard image. Is there a specific reason, why a single sync is not
sufficient to write the data to disk?

Furthermore calling sync will flush all filesystem buffers on the system. It
maybe a performance bottleneck because this may fill up the disk controller
capacity quickly.

Kind regards,
Stefan
---
 classes/image_types_fsl.bbclass | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/classes/image_types_fsl.bbclass b/classes/image_types_fsl.bbclass
index 75eca59..1ebcb06 100644
--- a/classes/image_types_fsl.bbclass
+++ b/classes/image_types_fsl.bbclass
@@ -178,8 +178,8 @@ generate_imx_sdcard () {
 	fi
 
 	# Burn Partition
-	dd if=${WORKDIR}/boot.img of=${SDCARD} conv=notrunc seek=1 bs=$(expr ${IMAGE_ROOTFS_ALIGNMENT} \* 1024) && sync && sync
-	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024) && sync && sync
+	dd if=${WORKDIR}/boot.img of=${SDCARD} conv=notrunc,fsync seek=1 bs=$(expr ${IMAGE_ROOTFS_ALIGNMENT} \* 1024)
+	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc,fsync seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024)
 }
 
 #
@@ -293,7 +293,7 @@ generate_mxs_sdcard () {
 
 	parted ${SDCARD} print
 
-	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024) && sync && sync
+	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc,fsync seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024)
 }
 
 IMAGE_CMD_sdcard () {
-- 
1.9.1

Re: [meta-fsl-arm][PATCH] classes: use dd's option fsync instead of sync

[Nikolay Dimitrov]

On 05/05/2015 11:40 AM, Stefan Christ wrote:
> The shell command sync flushes all filesystem buffers in the system.  On
> a bigger multiuser system there are multiple gigs of data sometimes in
> the buffer which then are written out to disk at once.  It's better to
> only flush the specific file with dd's option 'fsync'.
>
> Signed-off-by: Stefan Christ <s.christ@phytec.de>
> ---
> Hi,
>
> I'm curious why the bbclass image_types_fsl.bbclass uses a double 'sync' to
> burn the sdcard image. Is there a specific reason, why a single sync is not
> sufficient to write the data to disk?
>
> Furthermore calling sync will flush all filesystem buffers on the system. It
> maybe a performance bottleneck because this may fill up the disk controller
> capacity quickly.
>
> Kind regards,
> Stefan
> ---
>   classes/image_types_fsl.bbclass | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/classes/image_types_fsl.bbclass b/classes/image_types_fsl.bbclass
> index 75eca59..1ebcb06 100644
> --- a/classes/image_types_fsl.bbclass
> +++ b/classes/image_types_fsl.bbclass
> @@ -178,8 +178,8 @@ generate_imx_sdcard () {
>   	fi
>
>   	# Burn Partition
> -	dd if=${WORKDIR}/boot.img of=${SDCARD} conv=notrunc seek=1 bs=$(expr ${IMAGE_ROOTFS_ALIGNMENT} \* 1024) && sync && sync
> -	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024) && sync && sync
> +	dd if=${WORKDIR}/boot.img of=${SDCARD} conv=notrunc,fsync seek=1 bs=$(expr ${IMAGE_ROOTFS_ALIGNMENT} \* 1024)
> +	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc,fsync seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024)
>   }
>
>   #
> @@ -293,7 +293,7 @@ generate_mxs_sdcard () {
>
>   	parted ${SDCARD} print
>
> -	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024) && sync && sync
> +	dd if=${SDCARD_ROOTFS} of=${SDCARD} conv=notrunc,fsync seek=1 bs=$(expr ${BOOT_SPACE_ALIGNED} \* 1024 + ${IMAGE_ROOTFS_ALIGNMENT} \* 1024)
>   }
>
>   IMAGE_CMD_sdcard () {
>

Tested-by: Nikolay Dimitrov <picmaster@mail.bg>