RFR: 8264412: AArch64: CPU description should refer DMI
Yasumasa Suenaga
ysuenaga at openjdk.java.net
Tue Mar 30 10:47:52 UTC 2021
On Tue, 30 Mar 2021 08:45:37 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:
>> `jdk.CPUInformation` event on AArch64 has valid CPU description in [JDK-8262491](https://bugs.openjdk.java.net/browse/JDK-8262491), however it does not work on UEFI booted machine.
>>
>> [JDK-8262491](https://bugs.openjdk.java.net/browse/JDK-8262491) refers device tree to get board name, however it does not exist on UEFI. We need to refer DMI.
>> However we need to have root privilege, so we refer /sys/devices/virtual/dmi/id to avoid it.
>>
>> We can get board name from /sys/devices/virtual/dmi/id/board_name, but some machine set empty string to it. So we will refer /sys/devices/virtual/dmi/id/product_name as a fallback.
>>
>> For example, we can get following CPU description on AWS A1 instance after this change:
>>
>> jdk.CPUInformation {
>> startTime = 05:28:24.506
>> cpu = "AArch64"
>> description = "AArch64 a1.2xlarge 0x41:0x0:0xd08:3, simd, crc, aes, sha1, sha256"
>> sockets = 8
>> cores = 8
>> hwThreads = 8
>> }
>
> src/hotspot/os_cpu/linux_aarch64/vm_version_linux_aarch64.cpp line 196:
>
>> 194: if (!read_fully("/proc/device-tree/compatible", buf, buflen)) {
>> 195: if (!read_fully("/sys/devices/virtual/dmi/id/board_name", buf, buflen)) {
>> 196: read_fully("/sys/devices/virtual/dmi/id/product_name", buf, buflen);
>
> I think it would be nicer to write:
>
> if (read_fully("/proc/device-tree/compatible", buf, buflen)) {
> return;
> }
> if (read_fully("/sys/devices/virtual/dmi/id/board_name", buf, buflen)) {
> return;
> }
> read_fully("/sys/devices/virtual/dmi/id/product_name", buf, buflen);
> ...in case we would add more lines afterwards.
I changed it in new commit.
-------------
PR: https://git.openjdk.java.net/jdk/pull/3259
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