Fix some issues in the thread cap logic
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Panu Matilainen
parent
dce71ded33
commit
48ff1fa7e0
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@ -1,10 +1,8 @@
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From 4c772fcf7114d6ce20800c12bc377b490d267548 Mon Sep 17 00:00:00 2001
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Message-Id: <4c772fcf7114d6ce20800c12bc377b490d267548.1566558648.git.pmatilai@redhat.com>
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In-Reply-To: <4d16d81a1af3e43b8392e7c335f616c9c0c6e41b.1566558648.git.pmatilai@redhat.com>
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References: <4d16d81a1af3e43b8392e7c335f616c9c0c6e41b.1566558648.git.pmatilai@redhat.com>
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From fa70eaa852aab38857b3c8663386e8759f121bbe Mon Sep 17 00:00:00 2001
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Message-Id: <fa70eaa852aab38857b3c8663386e8759f121bbe.1566904946.git.pmatilai@redhat.com>
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From: Panu Matilainen <pmatilai@redhat.com>
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Date: Fri, 23 Aug 2019 11:17:21 +0300
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Subject: [PATCH 2/2] Cap number of threads on 32bit platforms, add a tunable
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Subject: [PATCH] Cap number of threads on 32bit platforms, add tunables
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(RhBug:1729382)
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On 32bit plaforms, address space is easily exhausted with multiple
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@ -13,44 +11,67 @@ Simply cap the number of threads to maximum of four on any 32bit
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platform to play it safe. It's still three more than we were able to
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use on older releases...
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In addition, introduce a separate tunable for tweaking the maximum
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number of threads just in case, defaulting to max CPUs available.
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In addition, introduce tunables for controlling the number of threads
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used similarly to what is available for number of CPUs: forced number
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and a separate ceiling.
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The max logic gets surprisingly tricky with the mixed OMP and rpm
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tunables and different semantics. Notably, OMP does not have a nice
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way to set a maximum from inside a program (this is only possible
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from an environment variable so we can't use it here), so we need
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to jump through a lot of hoops to figure out whether an *unlimited*
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setting would go above the platform limitation. I'm not entirely
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convinced this is 100% bulletproof, but then it's all going to change
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and become even more complicated when we start taking memory limitations
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into account...
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---
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build/parseSpec.c | 10 +++++++++-
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platform.in | 3 +++
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2 files changed, 12 insertions(+), 1 deletion(-)
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build/parseSpec.c | 20 +++++++++++++++++---
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platform.in | 5 +++++
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2 files changed, 22 insertions(+), 3 deletions(-)
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diff --git a/build/parseSpec.c b/build/parseSpec.c
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index 737a1233c..ab3ba9cae 100644
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index 737a1233c..ed5c3ef63 100644
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--- a/build/parseSpec.c
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+++ b/build/parseSpec.c
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@@ -1035,7 +1035,15 @@ static rpmSpec parseSpec(const char *specFile, rpmSpecFlags flags,
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@@ -1035,9 +1035,23 @@ static rpmSpec parseSpec(const char *specFile, rpmSpecFlags flags,
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#ifdef ENABLE_OPENMP
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/* Set number of OMP threads centrally */
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- int ncpus = rpmExpandNumeric("%{?_smp_build_ncpus}");
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+ int ncpus = rpmExpandNumeric("%{?_smp_nthreads_max}");
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- if (ncpus > 0)
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- omp_set_num_threads(ncpus);
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+ int nthreads = rpmExpandNumeric("%{?_smp_build_nthreads}");
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+ int nthreads_max = rpmExpandNumeric("%{?_smp_nthreads_max}");
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+ if (nthreads <= 0)
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+ nthreads = omp_get_max_threads();
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+ if (nthreads_max > 0 && nthreads > nthreads_max)
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+ nthreads = nthreads_max;
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+#if __WORDSIZE == 32
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+ /* On 32bit platforms, address space shortage is an issue. Play safe. */
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+ if (ncpus <= 0 || ncpus > 4) {
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+ ncpus = 4;
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+ int platlimit = 4;
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+ if (nthreads > platlimit) {
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+ nthreads = platlimit;
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+ rpmlog(RPMLOG_DEBUG,
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+ "limiting number of threads to %d due to platform\n", ncpus);
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+ "limiting number of threads to %d due to platform\n", platlimit);
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+ }
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+#endif
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if (ncpus > 0)
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omp_set_num_threads(ncpus);
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+ if (nthreads > 0)
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+ omp_set_num_threads(nthreads);
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#endif
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if (spec->clean == NULL) {
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diff --git a/platform.in b/platform.in
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index db6d2382f..c70f44193 100644
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index db6d2382f..61f5e18a0 100644
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--- a/platform.in
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+++ b/platform.in
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@@ -59,6 +59,9 @@
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@@ -59,6 +59,11 @@
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%_smp_mflags -j%{_smp_build_ncpus}
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+# Maximum number of CPU's to use for threads
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+%_smp_nthreads_max %{_smp_build_ncpus}
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+# Maximum number of threads to use when building, 0 for unlimited
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+#%_smp_nthreads_max 0
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+
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+%_smp_build_nthreads %{_smp_build_ncpus}
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+
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#==============================================================================
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# ---- Build policy macros.
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5
rpm.spec
5
rpm.spec
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@ -21,7 +21,7 @@
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%global rpmver 4.15.0
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%global snapver beta
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%global rel 5
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%global rel 6
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%global srcver %{version}%{?snapver:-%{snapver}}
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%global srcdir %{?snapver:testing}%{!?snapver:%{name}-%(echo %{version} | cut -d'.' -f1-2).x}
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@ -547,6 +547,9 @@ make check || (cat tests/rpmtests.log; exit 0)
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%doc doc/librpm/html/*
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%changelog
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* Tue Aug 27 2019 Panu Matilainen <pmatilai@redhat.com> - 4.15.0-0.beta.6
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- Fix some issues in the thread cap logic
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* Mon Aug 26 2019 Panu Matilainen <pmatilai@redhat.com> - 4.15.0-0.beta.5
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- Re-enable test-suite, temporarily disabled during alpha troubleshooting
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