66 lines
1.9 KiB
Diff
66 lines
1.9 KiB
Diff
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commit 46c524be975a108d2b8d1cadb95003b9c2670c8e
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Author: Laurent Dufour <ldufour@linux.ibm.com>
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Date: Thu Jun 29 16:41:37 2023 +0200
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ppc64_cpu: Support partial SMT level through SYS FS smt/control files
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The next kernel release will support partial SMT level [1] though the SYS
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FS file "devices/system/cpu/smt/control". This allows the SMT level to be
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recorded in the kernel. With the current SMT level stored in the kernel,
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when a new CPU is added, only the necessary threads are brought online.
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The legacy way to active threads through the SYS FS files
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'devices/system/cpu/cpu<n>/online', is still used in the case the new SYS
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FS API is not available. This allows compatibility with the previous kernel
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versions.
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[1] https://lore.kernel.org/linuxppc-dev/20230705145143.40545-1-ldufour@linux.ibm.com/
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Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
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diff --git a/src/ppc64_cpu.c b/src/ppc64_cpu.c
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index 5fdf86a..c33a293 100644
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--- a/src/ppc64_cpu.c
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+++ b/src/ppc64_cpu.c
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@@ -56,6 +56,8 @@
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#define DIAGNOSTICS_RUN_MODE 42
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#define CPU_OFFLINE -1
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+#define SYS_SMT_CONTROL "/sys/devices/system/cpu/smt/control"
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+
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#ifdef HAVE_LINUX_PERF_EVENT_H
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struct cpu_freq {
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int offline;
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@@ -360,6 +362,20 @@ static int is_dscr_capable(void)
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return 0;
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}
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+/*
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+ * Depends on kernel's CONFIG_HOTPLUG_CPU
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+ */
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+static int set_smt_control(int smt_state)
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+{
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+ if (set_attribute(SYS_SMT_CONTROL, "%d", smt_state)) {
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+ /* Silently ignore kernel not supporting this feature */
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+ if (errno != ENODEV)
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+ perror(SYS_SMT_CONTROL);
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+ return -1;
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+ }
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+ return 0;
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+}
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+
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static int do_smt(char *state, bool numeric)
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{
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int rc = 0;
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@@ -388,7 +404,9 @@ static int do_smt(char *state, bool numeric)
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return -1;
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}
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- rc = set_smt_state(smt_state);
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+ /* Try using smt/control if failing, fall back to the legacy way */
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+ if (set_smt_control(smt_state))
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+ rc = set_smt_state(smt_state);
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}
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return rc;
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