From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sergei Trofimovich Date: Sat, 20 Aug 2022 18:17:51 +0000 Subject: Re: [PATCH] ia64: fix clock_getre(CLOCK_MONOTONIC) to report ITC frequency Message-Id: <20220820191751.26b125af@nz> List-Id: References: <20220815054944.4130786-1-slyich@gmail.com> <20220817122103.ecbd08bd545385e5bf8e0d72@linux-foundation.org> In-Reply-To: <20220817122103.ecbd08bd545385e5bf8e0d72@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org On Wed, 17 Aug 2022 12:21:03 -0700 Andrew Morton wrote: > On Mon, 15 Aug 2022 06:49:44 +0100 Sergei Trofimovich wrote: > > > clock_gettime(CLOCK_MONOTONIC, &tp) is very precise on ia64 as it uses > > ITC (similar to rdtsc on x86). It's not quite a hrtimer as it is a few > > times slower than 1ns. Usually 2-3ns. > > > > clock_getres(CLOCK_MONOTONIC, &res) never reflected that fact and > > reported 0.04s precision (1/HZ value). > > > > In https://bugs.gentoo.org/596382 gstreamer's test suite failed loudly > > when it noticed precision discrepancy. > > > > Before the change: > > > > clock_getres(CLOCK_MONOTONIC, &res) reported 250Hz precision. > > > > After the change: > > > > clock_getres(CLOCK_MONOTONIC, &res) reports ITC (400Mhz) precision. > > > > The patch is based on matoro's fix. It adds a bit of explanation why we > > need to special-case arch-specific clock_getres(). > > > > It would be best (and nice) to include the original developer's > Signed-off-by: and to Cc Émeric Maschino if possible? > > Could you please take care of these paperwork issues? Sounds good! I'll use matoro's nickname as is for S-o-B the way matoro is comfortable with to share it. Will add Émeric in v2 and send out in a few minutes. -- Sergei