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