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Thu, 25 Jun 2026 01:23:23 -0700 (PDT) Date: Thu, 25 Jun 2026 10:23:22 +0200 From: Michal =?utf-8?Q?Koutn=C3=BD?= To: Joe Simmons-Talbott Cc: Tejun Heo , Johannes Weiner , Shuah Khan , cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] selftests/cgroup: Adjust cpu test duration based on HZ Message-ID: References: <20260624160358.430354-1-joest@redhat.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="omrw3ip3e232dwpc" Content-Disposition: inline In-Reply-To: <20260624160358.430354-1-joest@redhat.com> --omrw3ip3e232dwpc Content-Type: text/plain; protected-headers=v1; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v3] selftests/cgroup: Adjust cpu test duration based on HZ MIME-Version: 1.0 Hi. On Wed, Jun 24, 2026 at 12:03:57PM -0400, Joe Simmons-Talbott wrote: > +/* > + * Best effort attempt to get the kernel's HZ value from the config. > + * Return the HZ value if found otherwise return -1 to indicate failure. > + */ > +static long > +_get_config_hz(void) drop underscore from the static function > +{ > + long hz =3D -1; use the default 1000 here to simplify the callers > + FILE *f; > + char cmd[256] =3D "zcat /proc/config.gz 2>/dev/null | grep '^CONFIG_HZ= =3D'"; > + > + f =3D popen(cmd, "r"); > + > + if (!f) > + return hz; > + > + if (fscanf(f, "CONFIG_HZ=3D%ld", &hz) =3D=3D EOF) > + goto out; > + > +out: > + pclose(f); > + return hz; > +} > + > /* > * This test creates a cgroup with some maximum value within a period, a= nd > * verifies that a process in the cgroup is not overscheduled. > @@ -646,15 +670,21 @@ test_cpucg_nested_weight_underprovisioned(const cha= r *root) > static int test_cpucg_max(const char *root) > { > int ret =3D KSFT_FAIL; > + long hz =3D _get_config_hz(); > long quota_usec =3D 1000; > long default_period_usec =3D 100000; /* cpu.max's default period */ > - long duration_seconds =3D 1; > + long duration_seconds; > =20 > - long duration_usec =3D duration_seconds * USEC_PER_SEC; > + long duration_usec; > long usage_usec, n_periods, remainder_usec, expected_usage_usec; > char *cpucg; > char quota_buf[32]; > =20 > + if (hz =3D=3D -1) > + hz =3D 1000; > + duration_seconds =3D 1000 / hz; > + duration_usec =3D duration_seconds * USEC_PER_SEC; I'd do the calculation in usecs duration_usec =3D duration_seconds * USEC_PER_SEC * 1000 / hz; so that actual duration is more precise (for hz=3D300 which is the only that doesn't divide 1000) All in all, make the adjustments for HZ with less code (since I expect this will need adjustments for SMPs in future). Thanks, Michal --omrw3ip3e232dwpc Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iJEEABYKADkWIQRCE24Fn/AcRjnLivR+PQLnlNv4CAUCajzldhsUgAAAAAAEAA5t YW51MiwyLjUrMS4xMiwyLDIACgkQfj0C55Tb+AhG5AEAsiaZILB8jz1XPZq6anV8 Hc6J1Y5Pv7YWDyBDDQXko2EA/3VvrRbv6LPfgIy+hXnRfjhjxl4i1e2WobK0WYIe V/0A =0a5l -----END PGP SIGNATURE----- --omrw3ip3e232dwpc--