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4d92f50249
Christian Borntraeger reported that the now missing diag 44 calls (voluntary
time slice end) does cause a performance regression for stop_machine() calls
if a machine has more virtual cpus than the host has physical cpus.
This patch mainly reverts 57f2ffe14f ("s390: remove diag 44 calls from
cpu_relax()") with the exception that we still do not issue diag 44 calls if
running with smt enabled. Due to group scheduling algorithms when running in
LPAR this would lead to significant latencies.
However, when running in LPAR we do not have more virtual than physical cpus.
Reported-and-tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
104 lines
2.3 KiB
C
104 lines
2.3 KiB
C
/*
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* Copyright IBM Corp. 2008
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* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
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*/
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#define KMSG_COMPONENT "cpu"
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#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/seq_file.h>
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#include <linux/delay.h>
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#include <linux/cpu.h>
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#include <asm/elf.h>
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#include <asm/lowcore.h>
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#include <asm/param.h>
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#include <asm/smp.h>
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static DEFINE_PER_CPU(struct cpuid, cpu_id);
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void cpu_relax(void)
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{
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if (!smp_cpu_mtid && MACHINE_HAS_DIAG44)
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asm volatile("diag 0,0,0x44");
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barrier();
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}
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EXPORT_SYMBOL(cpu_relax);
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/*
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* cpu_init - initializes state that is per-CPU.
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*/
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void cpu_init(void)
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{
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struct cpuid *id = this_cpu_ptr(&cpu_id);
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get_cpu_id(id);
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atomic_inc(&init_mm.mm_count);
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current->active_mm = &init_mm;
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BUG_ON(current->mm);
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enter_lazy_tlb(&init_mm, current);
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}
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/*
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* show_cpuinfo - Get information on one CPU for use by procfs.
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*/
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static int show_cpuinfo(struct seq_file *m, void *v)
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{
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static const char *hwcap_str[] = {
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"esan3", "zarch", "stfle", "msa", "ldisp", "eimm", "dfp",
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"edat", "etf3eh", "highgprs", "te", "vx"
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};
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unsigned long n = (unsigned long) v - 1;
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int i;
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if (!n) {
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s390_adjust_jiffies();
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seq_printf(m, "vendor_id : IBM/S390\n"
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"# processors : %i\n"
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"bogomips per cpu: %lu.%02lu\n",
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num_online_cpus(), loops_per_jiffy/(500000/HZ),
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(loops_per_jiffy/(5000/HZ))%100);
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seq_puts(m, "features\t: ");
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for (i = 0; i < ARRAY_SIZE(hwcap_str); i++)
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if (hwcap_str[i] && (elf_hwcap & (1UL << i)))
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seq_printf(m, "%s ", hwcap_str[i]);
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seq_puts(m, "\n");
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show_cacheinfo(m);
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}
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get_online_cpus();
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if (cpu_online(n)) {
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struct cpuid *id = &per_cpu(cpu_id, n);
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seq_printf(m, "processor %li: "
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"version = %02X, "
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"identification = %06X, "
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"machine = %04X\n",
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n, id->version, id->ident, id->machine);
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}
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put_online_cpus();
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return 0;
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}
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static void *c_start(struct seq_file *m, loff_t *pos)
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{
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return *pos < nr_cpu_ids ? (void *)((unsigned long) *pos + 1) : NULL;
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}
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static void *c_next(struct seq_file *m, void *v, loff_t *pos)
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{
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++*pos;
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return c_start(m, pos);
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}
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static void c_stop(struct seq_file *m, void *v)
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{
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}
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const struct seq_operations cpuinfo_op = {
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.start = c_start,
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.next = c_next,
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.stop = c_stop,
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.show = show_cpuinfo,
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};
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