117 lines
3.8 KiB
Diff
117 lines
3.8 KiB
Diff
From 2d910eecf10cd806e22abeb1d96189f87ef74d91 Mon Sep 17 00:00:00 2001
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From: John Stultz <jstultz@google.com>
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Date: Thu, 28 Jul 2022 20:22:36 +0000
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Subject: [PATCH] cyclictest: Fix threads being affined even when -a isn't set
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Using cyclictest without specifying affinity via -a, I was
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noticing a strange issue where the rt threads where not
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migrating when being blocked.
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After lots of debugging in the kernel, I found its actually an
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issue with cyclictest.
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When using -t there is no behavioral difference between specifying
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-a or not specifying -a.
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This can be confirmed by adding printf messages around the
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pthread_setaffinity_np() call in the threadtest function.
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Currently:
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root@localhost:~/rt-tests# ./cyclictest -t -a -q -D1
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Affining thread 0 to cpu: 0
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Affining thread 1 to cpu: 1
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Affining thread 2 to cpu: 2
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Affining thread 3 to cpu: 3
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Affining thread 4 to cpu: 4
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Affining thread 5 to cpu: 5
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Affining thread 7 to cpu: 7
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Affining thread 6 to cpu: 6
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T: 0 (15034) P: 0 I:1000 C: 1000 Min: 82 Act: 184 Avg: 180 Max: 705
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...
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root@localhost:~/rt-tests# ./cyclictest -t -q -D1
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Affining thread 0 to cpu: 0
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Affining thread 1 to cpu: 1
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Affining thread 2 to cpu: 2
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Affining thread 3 to cpu: 3
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Affining thread 4 to cpu: 4
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Affining thread 5 to cpu: 5
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Affining thread 6 to cpu: 6
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Affining thread 7 to cpu: 7
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T: 0 (15044) P: 0 I:1000 C: 1000 Min: 74 Act: 144 Avg: 162 Max: 860
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..
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This issue seems to come from the logic in process_options():
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/* if smp wasn't requested, test for numa automatically */
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if (!smp) {
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numa = numa_initialize();
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if (setaffinity == AFFINITY_UNSPECIFIED)
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setaffinity = AFFINITY_USEALL;
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}
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Here, by setting setaffinity = AFFINITY_USEALL, we effectively
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pin each thread to its respective cpu, same as the "-a" option.
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This was most recently introduced in commit bdb8350f1b0b
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("Revert "cyclictest: Use affinity_mask for steering
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thread placement"").
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This seems erronious to me, so I wanted to share this patch
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which removes the overriding AFFINITY_UNSPECIFIED with
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AFFINITY_USEALL by default. Also, some additional tweaks to
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preserve the existing numa allocation affinity.
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With this patch, we no longer call pthread_setaffinity_np() in the
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"./cyclictest -t -q -D1" case.
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Cc: John Kacur <jkacur@redhat.com>
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Cc: Connor O'Brien <connoro@google.com>
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Cc: Qais Yousef <qais.yousef@arm.com>
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Signed-off-by: John Stultz <jstultz@google.com>
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Signed-off-by: John Kacur <jkacur@redhat.com>
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---
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src/cyclictest/cyclictest.c | 10 ++++++----
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1 file changed, 6 insertions(+), 4 deletions(-)
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diff --git a/src/cyclictest/cyclictest.c b/src/cyclictest/cyclictest.c
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index decea786268a..82759d1cf67b 100644
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--- a/src/cyclictest/cyclictest.c
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+++ b/src/cyclictest/cyclictest.c
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@@ -1270,8 +1270,6 @@ static void process_options(int argc, char *argv[], int max_cpus)
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/* if smp wasn't requested, test for numa automatically */
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if (!smp) {
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numa = numa_initialize();
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- if (setaffinity == AFFINITY_UNSPECIFIED)
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- setaffinity = AFFINITY_USEALL;
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}
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if (option_affinity) {
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@@ -2043,9 +2041,13 @@ int main(int argc, char **argv)
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void *stack;
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void *currstk;
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size_t stksize;
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+ int node_cpu = cpu;
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+
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+ if (node_cpu == -1)
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+ node_cpu = cpu_for_thread_ua(i, max_cpus);
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/* find the memory node associated with the cpu i */
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- node = rt_numa_numa_node_of_cpu(cpu);
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+ node = rt_numa_numa_node_of_cpu(node_cpu);
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/* get the stack size set for this thread */
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if (pthread_attr_getstack(&attr, &currstk, &stksize))
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@@ -2056,7 +2058,7 @@ int main(int argc, char **argv)
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stksize = PTHREAD_STACK_MIN * 2;
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/* allocate memory for a stack on appropriate node */
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- stack = rt_numa_numa_alloc_onnode(stksize, node, cpu);
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+ stack = rt_numa_numa_alloc_onnode(stksize, node, node_cpu);
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/* touch the stack pages to pre-fault them in */
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memset(stack, 0, stksize);
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--
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2.37.2
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