Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
rseq: Move slice_ext_nsec to debugfs
Move changing the slice ext duration to debugfs, a sliglty less permanent
interface.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260121143207.923520192@infradead.org
+49
-35
-11
Documentation/admin-guide/sysctl/kernel.rst
-11
Documentation/admin-guide/sysctl/kernel.rst
···
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ROM/Flash boot loader. Maybe to tell it what to do after
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rebooting. ???
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-
rseq_slice_extension_nsec
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=========================
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-
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A task can request to delay its scheduling if it is in a critical section
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via the prctl(PR_RSEQ_SLICE_EXTENSION_SET) mechanism. This sets the maximum
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allowed extension in nanoseconds before scheduling of the task is enforced.
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Default value is 10000ns (10us). The possible range is 10000ns (10us) to
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50000ns (50us).
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This value has a direct correlation to the worst case scheduling latency;
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increment at your own risk.
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sched_energy_aware
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==================
+3
-1
Documentation/userspace-api/rseq.rst
+3
-1
Documentation/userspace-api/rseq.rst
···
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interrupted and the interrupt results in a reschedule request in the
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kernel, then the kernel can grant a time slice extension and return to
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userspace instead of scheduling out. The length of the extension is
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determined by the ``rseq_slice_extension_nsec`` sysctl.
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+
determined by debugfs:rseq/slice_ext_nsec. The default value is 10 usec; which
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is the minimum value. It can be incremented to 50 usecs, however doing so
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can/will affect the minimum scheduling latency.
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The kernel indicates the grant by clearing rseq::slice_ctrl::request and
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setting rseq::slice_ctrl::granted to 1. If there is a reschedule of the
+46
-23
kernel/rseq.c
+46
-23
kernel/rseq.c
···
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}
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#endif /* CONFIG_TRACEPOINTS */
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-
#ifdef CONFIG_DEBUG_FS
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#ifdef CONFIG_RSEQ_STATS
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DEFINE_PER_CPU(struct rseq_stats, rseq_stats);
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128
···
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.release = single_release,
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};
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+
static void rseq_slice_ext_init(struct dentry *root_dir);
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+
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static int __init rseq_debugfs_init(void)
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{
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struct dentry *root_dir = debugfs_create_dir("rseq", NULL);
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debugfs_create_file("debug", 0644, root_dir, NULL, &debug_ops);
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rseq_stats_init(root_dir);
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if (IS_ENABLED(CONFIG_RSEQ_SLICE_EXTENSION))
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rseq_slice_ext_init(root_dir);
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return 0;
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}
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__initcall(rseq_debugfs_init);
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-
#endif /* CONFIG_DEBUG_FS */
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static bool rseq_set_ids(struct task_struct *t, struct rseq_ids *ids, u32 node_id)
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{
···
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void *cookie;
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};
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unsigned int rseq_slice_ext_nsecs __read_mostly = 10 * NSEC_PER_USEC;
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static const unsigned int rseq_slice_ext_nsecs_min = 10 * NSEC_PER_USEC;
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static const unsigned int rseq_slice_ext_nsecs_max = 50 * NSEC_PER_USEC;
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unsigned int rseq_slice_ext_nsecs __read_mostly = rseq_slice_ext_nsecs_min;
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static DEFINE_PER_CPU(struct slice_timer, slice_timer);
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DEFINE_STATIC_KEY_TRUE(rseq_slice_extension_key);
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···
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return yielded;
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}
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-
#ifdef CONFIG_SYSCTL
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static const unsigned int rseq_slice_ext_nsecs_min = 10 * NSEC_PER_USEC;
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static const unsigned int rseq_slice_ext_nsecs_max = 50 * NSEC_PER_USEC;
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static int rseq_slice_ext_show(struct seq_file *m, void *p)
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{
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seq_printf(m, "%d\n", rseq_slice_ext_nsecs);
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return 0;
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}
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static const struct ctl_table rseq_slice_ext_sysctl[] = {
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{
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.procname = "rseq_slice_extension_nsec",
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.data = &rseq_slice_ext_nsecs,
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.maxlen = sizeof(unsigned int),
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.mode = 0644,
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.proc_handler = proc_douintvec_minmax,
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.extra1 = (unsigned int *)&rseq_slice_ext_nsecs_min,
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.extra2 = (unsigned int *)&rseq_slice_ext_nsecs_max,
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},
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static ssize_t rseq_slice_ext_write(struct file *file, const char __user *ubuf,
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size_t count, loff_t *ppos)
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{
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unsigned int nsecs;
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if (kstrtouint_from_user(ubuf, count, 10, &nsecs))
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return -EINVAL;
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if (nsecs < rseq_slice_ext_nsecs_min)
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return -ERANGE;
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if (nsecs > rseq_slice_ext_nsecs_max)
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return -ERANGE;
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+
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rseq_slice_ext_nsecs = nsecs;
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return count;
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}
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static int rseq_slice_ext_open(struct inode *inode, struct file *file)
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{
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return single_open(file, rseq_slice_ext_show, inode->i_private);
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}
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static const struct file_operations slice_ext_ops = {
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.open = rseq_slice_ext_open,
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.read = seq_read,
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.write = rseq_slice_ext_write,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static void rseq_slice_sysctl_init(void)
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static void rseq_slice_ext_init(struct dentry *root_dir)
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{
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if (rseq_slice_extension_enabled())
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register_sysctl_init("kernel", rseq_slice_ext_sysctl);
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debugfs_create_file("slice_ext_nsec", 0644, root_dir, NULL, &slice_ext_ops);
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}
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#else /* CONFIG_SYSCTL */
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static inline void rseq_slice_sysctl_init(void) { }
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#endif /* !CONFIG_SYSCTL */
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static int __init rseq_slice_cmdline(char *str)
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{
···
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hrtimer_setup(per_cpu_ptr(&slice_timer.timer, cpu), rseq_slice_expired,
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CLOCK_MONOTONIC, HRTIMER_MODE_REL_PINNED_HARD);
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}
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rseq_slice_sysctl_init();
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return 0;
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}
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device_initcall(rseq_slice_init);
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+
#else
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static void rseq_slice_ext_init(struct dentry *root_dir) { }
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#endif /* CONFIG_RSEQ_SLICE_EXTENSION */