From: Markus Armbruster <armbru@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Peter Maydell <peter.maydell@linaro.org>,
qemu-block@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>,
qemu-devel@nongnu.org, Max Reitz <mreitz@redhat.com>,
David Edmondson <david.edmondson@oracle.com>,
Shannon Zhao <shannon.zhaosl@gmail.com>,
qemu-arm@nongnu.org, Igor Mammedov <imammedo@redhat.com>,
John Snow <jsnow@redhat.com>
Subject: Re: [RFC PATCH 0/5] ARM: reduce the memory consumed when mapping UEFI flash images
Date: Mon, 16 Nov 2020 14:48:26 +0100 [thread overview]
Message-ID: <87a6vhxvit.fsf@dusky.pond.sub.org> (raw)
In-Reply-To: <3da830b6-8200-6df9-9ba3-1f51bf887c4e@redhat.com> ("Philippe =?utf-8?Q?Mathieu-Daud=C3=A9=22's?= message of "Mon, 16 Nov 2020 12:39:46 +0100")
Philippe Mathieu-Daudé <philmd@redhat.com> writes:
> Hi David,
>
> On 11/16/20 11:42 AM, David Edmondson wrote:
>> Currently ARM UEFI images are typically built as 2MB/768kB flash
>> images for code and variables respectively. These images are both then
>> padded out to 64MB before being loaded by QEMU.
>>
>> Because the images are 64MB each, QEMU allocates 128MB of memory to
>> read them, and then proceeds to read all 128MB from disk (dirtying the
>> memory). Of this 128MB less than 3MB is useful - the rest is zero
>> padding.
>
> 2 years ago I commented the same problem, and suggested to access the
> underlying storage by "block", as this is a "block storage".
>
> Back then the response was "do not try to fix something that works".
> This is why we choose the big hammer "do not accept image size not
> matching device size" way.
>
> While your series seems to help, it only postpone the same
> implementation problem. If what you want is use the least memory
> required, I still believe accessing the device by block is the
> best approach.
"Do not try to fix something that works" is hard to disagree with.
However, at least some users seem to disagree with "this works". Enough
to overcome the resistance to change?
next prev parent reply other threads:[~2020-11-16 13:49 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-16 10:42 [RFC PATCH 0/5] ARM: reduce the memory consumed when mapping UEFI flash images David Edmondson
2020-11-16 10:42 ` [RFC PATCH 1/5] hw/block: blk_check_size_and_read_all should report backend name David Edmondson
2020-11-16 11:23 ` Philippe Mathieu-Daudé
2020-11-16 13:29 ` David Edmondson
2020-11-19 11:56 ` Alex Bennée
2020-11-16 10:42 ` [RFC PATCH 2/5] hw/block: Flash images can be smaller than the device David Edmondson
2020-11-16 10:42 ` [RFC PATCH 3/5] hw/arm: Convert assertions about flash image size to error_report David Edmondson
2020-11-19 11:39 ` Alex Bennée
2020-11-16 10:42 ` [RFC PATCH 4/5] hw/arm: Flash image mapping follows image size David Edmondson
2020-11-16 10:42 ` [RFC PATCH 5/5] hw/arm: Only minimise flash size on older machines David Edmondson
2020-11-16 11:39 ` [RFC PATCH 0/5] ARM: reduce the memory consumed when mapping UEFI flash images Philippe Mathieu-Daudé
2020-11-16 13:43 ` David Edmondson
2020-11-16 13:48 ` Markus Armbruster [this message]
2020-11-19 6:09 ` Philippe Mathieu-Daudé
2020-11-19 11:45 ` Alex Bennée
2020-11-19 11:57 ` Philippe Mathieu-Daudé
2020-12-07 12:07 ` David Edmondson
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