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Re: [PATCH] Use direct I/O for loop devices
- To: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 18 Aug 2022 16:12:10 +0200
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- Cc: Wei Liu <wl@xxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, Xen developer discussion <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 18 Aug 2022 14:12:20 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 18.08.2022 16:04, Demi Marie Obenour wrote:
> On Thu, Aug 18, 2022 at 09:02:11AM +0200, Jan Beulich wrote:
>> On 17.08.2022 22:46, Demi Marie Obenour wrote:
>>> --- a/tools/hotplug/Linux/block
>>> +++ b/tools/hotplug/Linux/block
>>> @@ -330,7 +330,7 @@ mount it read-write in a guest domain."
>>> else
>>> roflag=''
>>> fi
>>> - do_or_die losetup $roflag "$loopdev" "$file"
>>> + do_or_die losetup --direct-io=on $roflag "$loopdev" "$file"
>>
>> I guess you want to first check (maybe in tools/configure) that losetup
>> actually supports that option. The old-ish one I'm looking at doesn't,
>> according to its --help output at least.
>
> What version are you referring to?
The tool itself doesn't recognize --version. It originates from
util-linux 2.19.1 from all I can tell.
> In Qubes OS the current plan is to use a block “script” written in C, to
> improve performance and (when combined with kernel patches) eliminate
> race conditions. This code could be made a wrapper for the C version.
Is this relevant here in some way I don't recognize, or did you say this
only to provide some further background info?
Jan
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