On 2023-09-02 12:27, jeff via Cygwin wrote:
On 9/2/2023 10:56, Brian Inglis wrote:
On 2023-09-02 08:57, jeff via Cygwin wrote:
I have a program that is embarrassing parallel.
On my older computer which has an epyc 7302 (16 cores, 32 threads) it scales
very well using cygwin, and fully utilized all threads.
On my new computer which has an epyc 7B13 (64 cores, 128 threads) it does not
scale very well.
According to the windows task manager, it only uses 74% of the cpu resources.
The time it takes the program to run on windows is 166 seconds.
Using the same hardware on a recent version of linux, I can get 100% cpu
utilization and the program takes 100 seconds to run.
I suspect there may be something in cygwin that doesn't scale well with lots
of posix threads.
Both Windows and Cygwin support multiple processor groups, as some developers,
maintainers, and users need support on such systems, and the process and thread
support has been added to Cygwin.
I know this is a bit of an unusual situation, but you can buy a 128 core /
256 thread system now.
Enclosed is the output of cygcheck.
I updated my version of cygwin to be current as of today, Sep 2 2023.
What Windows edition and version are you running?
For details run:
$ reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion" \
| sed '/^\s\+\.*\s/!d;/^.\{80,\}/d'
Some retail editions limit you to 64 threads and that seems to be your case:
NUMBER_OF_PROCESSORS = '64'
To make full use of your processors, you may have to upgrade your Windows to a
commercial licence (and installation) of Windows 10/11 Pro for Workstations,
enabling server features on non-server "Worskations" ~ HEDTs (High-End
DeskTops); see:
https://www.anandtech.com/show/15483/amd-threadripper-3990x-review/3
or just run Linux!
Watch out for terms misused like processor == socket on some sites!
Also, you have to consider these are server systems, mainly designed for VM
not HPC (High Performance Computing) parallelism.
Your older system has higher base and boost/turbo clocks 3.0-3.3GHz: your
newer system has lower clocks 2.25-2.65/3/3.5GHz which seems to depend on OEM
target.
You may also need to upgrade your memory, as each core could run ~10GB/s
instructions, and these workstations are often provisioned with 128-256GB
(2-4GB/core), so that may also need a Windows edition upgrade.
I am running windows 10 professional. Using the task manager, 64 cores and 128
threads shows up for my processor.
As the linked AnandTech article shows and explains with Task Manager/
Performance tab, Win 10 Pro may think you have dual sockets, that limits the
maximum thread parallelism you can achieve:
"Now the thing is, Workstation and Enterprise are built with multiple processor
groups in mind, whereas Pro is not."
Here is the output of your regex:
SystemRoot REG_SZ C:\Windows
BaseBuildRevisionNumber REG_DWORD 0x1
BuildBranch REG_SZ vb_release
BuildGUID REG_SZ ffffffff-ffff-ffff-ffff-ffffffffffff
BuildLab REG_SZ 19041.vb_release.191206-1406
BuildLabEx REG_SZ 19041.1.amd64fre.vb_release.191206-1406
CompositionEditionID REG_SZ Enterprise
CurrentBuild REG_SZ 19045
CurrentBuildNumber REG_SZ 19045
CurrentMajorVersionNumber REG_DWORD 0xa
CurrentMinorVersionNumber REG_DWORD 0x0
CurrentType REG_SZ Multiprocessor Free
CurrentVersion REG_SZ 6.3
EditionID REG_SZ Professional
EditionSubManufacturer REG_SZ
EditionSubstring REG_SZ
EditionSubVersion REG_SZ
InstallationType REG_SZ Client
InstallDate REG_DWORD 0x61e2300a
ProductName REG_SZ Windows 10 Pro
ReleaseId REG_SZ 2009
SoftwareType REG_SZ System
UBR REG_DWORD 0xcfc
PathName REG_SZ C:\Windows
ProductId REG_SZ 00330-80000-00000-AA073
DisplayVersion REG_SZ 22H2
RegisteredOwner REG_SZ jdeifik
RegisteredOrganization REG_SZ
InstallTime REG_QWORD 0x1d809b6d4ce7b09
In practice, but the new and old processors typically run at about 3ghz when
under load.
When idling, both processors use about the same amount of power.
I have 128gb of ram, in 4 slots. Using that configuration, I can get 100% load
and significant faster performance on linux.
Therefore I conclude the issue is either with windows or cygwin, and is not a
hardware issue.
>
When I run cinebench, I can get to 100% cpu utulization (at around 3ghz) on
windows.
Chances are the benchmark is designed to handle that:
"When the program is running inside the group, unless it is processor group
aware, then it can only access other threads in the same group. This means that
if a multi-threaded program can use 128 threads, if it isn’t built with
processor groups in mind, then it might only spawn with access to 64."
I also do not know how you would program for that in Cygwin to map onto the
equivalent Windows function required.
Perhaps one of the developers involved could comment here?
As for what the processors are 'designed' for, I really don't care.
I want a reliable, fast computer with ECC memory, and I can get that with an
EPYC processor.
If a workload needs more than 128gb of memory, you pretty much need to use
server processors.
I can put in up to 2tb of memory in my system, if I have the need for that.
As I suggested above, and as the AT tests suggest, with your configuration, you
may get better results disabling multithreading on your current system, or
running Pro for Workstations, which you may be able to test using a generic key.
Pro for Workstations is used and recommended by video shops, with much lower
costs and power consumption running AMD than Intel, as a designer's workstation
alternative getting better performance and reponsiveness than using servers for
the same task.
--
Take care. Thanks, Brian Inglis Calgary, Alberta, Canada
La perfection est atteinte Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer but when there is no more to cut
-- Antoine de Saint-Exupéry
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