ACK: [SRU][Jammy][PATCH 0/1] turbostat fails with too many open files on large systems

[Manuel Diewald]

On Tue, Aug 27, 2024 at 12:42:05PM +1200, Matthew Ruffell wrote:
> BugLink: https://bugs.launchpad.net/bugs/2069961
> 
> [Impact]
> 
> On large systems, e.g. with 512 cpus or more, turbostat fails to run due to
> exceeding the rlimit for number of files. 512 cpus requires 1028 file
> descriptors, but the current limit is 999.
> 
> $ lscpu
> ...
> CPU(s):                  512
>   On-line CPU(s) list:   0-511
> ...
> 
> $ sudo turbostat
> ...
> turbostat: /sys/devices/system/cpu/cpu477/cpuidle/state0/usage: open failed: Too many open files
> 
> There is no workaround, apart from maybe using powerstat instead.
> 
> [Fix]
> 
> The fix is to increase the rlimit to increase the amount of file descriptors
> that turbostat can open to 2^15, which should be plenty for some time to come.
> 
> commit 3ac1d14d0583a2de75d49a5234d767e2590384dd
> Author: Wyes Karny <wyes.karny at amd.com>
> Date:   Tue Oct 3 05:07:51 2023 +0000
> Subject: tools/power turbostat: Increase the limit for fd opened
> Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3ac1d14d0583a2de75d49a5234d767e2590384dd
> 
> This landed in 6.9-rc4, and requires a backport for minor context adjustment in
> the first hunk for jammy. Noble got fixed already through upstream stable.
> 
> [Testcase]
> 
> Deploy a bare metal system with 512 or more cpus.
> 
> Install linux-tools:
> 
> $ sudo apt install linux-tools-$(uname -r)
> 
> Run turbostat:
> 
> $ sudo turbostat
> ...
> turbostat: /sys/devices/system/cpu/cpu477/cpuidle/state0/usage: open failed: Too many open files
> 
> There are test kernels available in the following ppa:
> 
> https://launchpad.net/~mruffell/+archive/ubuntu/sf388491-test
> 
> If you install them, you should be able to see normal turbostat output for all
> cpus installed in the system.
> 
> [Where problems can occur]
> 
> We are simply increasing the rlimit for file descriptors that turbostat can
> open. This should have no impact on any existing systems.
> 
> If a regression should occur, then turbostat functionality might not work.
> Users could use powerstat instead as a workaround while things are fixed.
> 
> Wyes Karny (1):
>   tools/power turbostat: Increase the limit for fd opened
> 
>  tools/power/x86/turbostat/turbostat.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> -- 
> 2.45.2
> 
> 
> -- 
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team

Acked-by: Manuel Diewald <manuel.diewald at canonical.com>

-- 
 Manuel
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