82 lines
2.9 KiB
Diff
82 lines
2.9 KiB
Diff
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] 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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threads, causing arbitrary builds failure regressions (RhBug:1729382).
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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 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 | 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..ed5c3ef63 100644
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--- a/build/parseSpec.c
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+++ b/build/parseSpec.c
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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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- 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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+ 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", platlimit);
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+ }
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+#endif
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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..61f5e18a0 100644
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--- a/platform.in
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+++ b/platform.in
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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 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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#
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--
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2.21.0
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