forked from Minki/linux
cf9efce0ce
Currently, when CONFIG_VIRT_CPU_ACCOUNTING is enabled, we use the PURR register for measuring the user and system time used by processes, as well as other related times such as hardirq and softirq times. This turns out to be quite confusing for users because it means that a program will often be measured as taking less time when run on a multi-threaded processor (SMT2 or SMT4 mode) than it does when run on a single-threaded processor (ST mode), even though the program takes longer to finish. The discrepancy is accounted for as stolen time, which is also confusing, particularly when there are no other partitions running. This changes the accounting to use the timebase instead, meaning that the reported user and system times are the actual number of real-time seconds that the program was executing on the processor thread, regardless of which SMT mode the processor is in. Thus a program will generally show greater user and system times when run on a multi-threaded processor than on a single-threaded processor. On pSeries systems on POWER5 or later processors, we measure the stolen time (time when this partition wasn't running) using the hypervisor dispatch trace log. We check for new entries in the log on every entry from user mode and on every transition from kernel process context to soft or hard IRQ context (i.e. when account_system_vtime() gets called). So that we can correctly distinguish time stolen from user time and time stolen from system time, without having to check the log on every exit to user mode, we store separate timestamps for exit to user mode and entry from user mode. On systems that have a SPURR (POWER6 and POWER7), we read the SPURR in account_system_vtime() (as before), and then apportion the SPURR ticks since the last time we read it between scaled user time and scaled system time according to the relative proportions of user time and system time over the same interval. This avoids having to read the SPURR on every kernel entry and exit. On systems that have PURR but not SPURR (i.e., POWER5), we do the same using the PURR rather than the SPURR. This disables the DTL user interface in /sys/debug/kernel/powerpc/dtl for now since it conflicts with the use of the dispatch trace log by the time accounting code. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
269 lines
6.1 KiB
C
269 lines
6.1 KiB
C
/*
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* Virtual Processor Dispatch Trace Log
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*
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* (C) Copyright IBM Corporation 2009
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*
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* Author: Jeremy Kerr <jk@ozlabs.org>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/debugfs.h>
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#include <asm/smp.h>
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#include <asm/system.h>
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#include <asm/uaccess.h>
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#include <asm/firmware.h>
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#include <asm/lppaca.h>
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#include "plpar_wrappers.h"
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struct dtl {
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struct dtl_entry *buf;
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struct dentry *file;
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int cpu;
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int buf_entries;
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u64 last_idx;
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};
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static DEFINE_PER_CPU(struct dtl, cpu_dtl);
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/*
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* Dispatch trace log event mask:
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* 0x7: 0x1: voluntary virtual processor waits
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* 0x2: time-slice preempts
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* 0x4: virtual partition memory page faults
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*/
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static u8 dtl_event_mask = 0x7;
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/*
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* Size of per-cpu log buffers. Default is just under 16 pages worth.
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*/
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static int dtl_buf_entries = (16 * 85);
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static int dtl_enable(struct dtl *dtl)
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{
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unsigned long addr;
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int ret, hwcpu;
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/* only allow one reader */
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if (dtl->buf)
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return -EBUSY;
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/* we need to store the original allocation size for use during read */
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dtl->buf_entries = dtl_buf_entries;
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dtl->buf = kmalloc_node(dtl->buf_entries * sizeof(struct dtl_entry),
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GFP_KERNEL, cpu_to_node(dtl->cpu));
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if (!dtl->buf) {
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printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
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__func__, dtl->cpu);
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return -ENOMEM;
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}
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/* Register our dtl buffer with the hypervisor. The HV expects the
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* buffer size to be passed in the second word of the buffer */
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((u32 *)dtl->buf)[1] = dtl->buf_entries * sizeof(struct dtl_entry);
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hwcpu = get_hard_smp_processor_id(dtl->cpu);
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addr = __pa(dtl->buf);
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ret = register_dtl(hwcpu, addr);
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if (ret) {
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printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
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"failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
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kfree(dtl->buf);
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return -EIO;
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}
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/* set our initial buffer indices */
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dtl->last_idx = lppaca_of(dtl->cpu).dtl_idx = 0;
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/* ensure that our updates to the lppaca fields have occurred before
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* we actually enable the logging */
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smp_wmb();
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/* enable event logging */
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lppaca_of(dtl->cpu).dtl_enable_mask = dtl_event_mask;
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return 0;
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}
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static void dtl_disable(struct dtl *dtl)
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{
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int hwcpu = get_hard_smp_processor_id(dtl->cpu);
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lppaca_of(dtl->cpu).dtl_enable_mask = 0x0;
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unregister_dtl(hwcpu, __pa(dtl->buf));
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kfree(dtl->buf);
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dtl->buf = NULL;
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dtl->buf_entries = 0;
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}
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/* file interface */
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static int dtl_file_open(struct inode *inode, struct file *filp)
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{
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struct dtl *dtl = inode->i_private;
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int rc;
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rc = dtl_enable(dtl);
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if (rc)
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return rc;
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filp->private_data = dtl;
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return 0;
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}
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static int dtl_file_release(struct inode *inode, struct file *filp)
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{
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struct dtl *dtl = inode->i_private;
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dtl_disable(dtl);
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return 0;
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}
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static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
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loff_t *pos)
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{
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int rc, cur_idx, last_idx, n_read, n_req, read_size;
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struct dtl *dtl;
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if ((len % sizeof(struct dtl_entry)) != 0)
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return -EINVAL;
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dtl = filp->private_data;
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/* requested number of entries to read */
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n_req = len / sizeof(struct dtl_entry);
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/* actual number of entries read */
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n_read = 0;
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cur_idx = lppaca_of(dtl->cpu).dtl_idx;
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last_idx = dtl->last_idx;
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if (cur_idx - last_idx > dtl->buf_entries) {
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pr_debug("%s: hv buffer overflow for cpu %d, samples lost\n",
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__func__, dtl->cpu);
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}
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cur_idx %= dtl->buf_entries;
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last_idx %= dtl->buf_entries;
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/* read the tail of the buffer if we've wrapped */
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if (last_idx > cur_idx) {
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read_size = min(n_req, dtl->buf_entries - last_idx);
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rc = copy_to_user(buf, &dtl->buf[last_idx],
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read_size * sizeof(struct dtl_entry));
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if (rc)
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return -EFAULT;
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last_idx = 0;
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n_req -= read_size;
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n_read += read_size;
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buf += read_size * sizeof(struct dtl_entry);
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}
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/* .. and now the head */
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read_size = min(n_req, cur_idx - last_idx);
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rc = copy_to_user(buf, &dtl->buf[last_idx],
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read_size * sizeof(struct dtl_entry));
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if (rc)
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return -EFAULT;
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n_read += read_size;
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dtl->last_idx += n_read;
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return n_read * sizeof(struct dtl_entry);
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}
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static const struct file_operations dtl_fops = {
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.open = dtl_file_open,
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.release = dtl_file_release,
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.read = dtl_file_read,
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.llseek = no_llseek,
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};
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static struct dentry *dtl_dir;
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static int dtl_setup_file(struct dtl *dtl)
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{
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char name[10];
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sprintf(name, "cpu-%d", dtl->cpu);
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dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
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if (!dtl->file)
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return -ENOMEM;
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return 0;
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}
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static int dtl_init(void)
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{
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struct dentry *event_mask_file, *buf_entries_file;
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int rc, i;
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING
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/* disable this for now */
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return -ENODEV;
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#endif
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if (!firmware_has_feature(FW_FEATURE_SPLPAR))
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return -ENODEV;
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/* set up common debugfs structure */
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rc = -ENOMEM;
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dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
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if (!dtl_dir) {
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printk(KERN_WARNING "%s: can't create dtl root dir\n",
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__func__);
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goto err;
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}
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event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
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dtl_dir, &dtl_event_mask);
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buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0600,
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dtl_dir, &dtl_buf_entries);
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if (!event_mask_file || !buf_entries_file) {
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printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
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goto err_remove_dir;
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}
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/* set up the per-cpu log structures */
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for_each_possible_cpu(i) {
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struct dtl *dtl = &per_cpu(cpu_dtl, i);
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dtl->cpu = i;
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rc = dtl_setup_file(dtl);
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if (rc)
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goto err_remove_dir;
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}
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return 0;
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err_remove_dir:
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debugfs_remove_recursive(dtl_dir);
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err:
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return rc;
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}
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arch_initcall(dtl_init);
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