[PATCH 3/3] powerpc: Add virtual processor dispatch trace log
Jeremy Kerr
jk at ozlabs.org
Thu Mar 12 14:55:52 EST 2009
pseries SPLPAR machines are able to retrieve a log of dispatch and
preempt events from the hypervisor. With this information, we can
see when and why each dispatch & preempt is occuring.
This change adds a set of debugfs files allowing userspace to read this
dispatch log.
Based on initial patches from Nishanth Aravamudan <nacc at us.ibm.com>.
Signed-off-by: Jeremy Kerr <jk at ozlabs.org>
---
arch/powerpc/platforms/pseries/Kconfig | 10
arch/powerpc/platforms/pseries/Makefile | 1
arch/powerpc/platforms/pseries/dtl.c | 274 ++++++++++++++++++++++++
arch/powerpc/platforms/pseries/plpar_wrappers.h | 10
4 files changed, 295 insertions(+)
diff --git a/arch/powerpc/platforms/pseries/Kconfig b/arch/powerpc/platforms/pseries/Kconfig
index ddc2a30..730a5cd 100644
--- a/arch/powerpc/platforms/pseries/Kconfig
+++ b/arch/powerpc/platforms/pseries/Kconfig
@@ -63,3 +63,13 @@ config CMM
makes sense for a system running in an LPAR where the unused pages
will be reused for other LPARs. The interface allows firmware to
balance memory across many LPARs.
+
+config DTL
+ bool "Dispatch Trace Log"
+ depends on PPC_SPLPAR && DEBUG_FS
+ help
+ SPLPAR machines can log hypervisor preempt & dispatch events to a
+ kernel buffer. Saying Y here will enable logging these events,
+ which are accessible through a debugfs file.
+
+ Say N if you are unsure.
diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index dfe574a..1b388b3 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -25,3 +25,4 @@ obj-$(CONFIG_HVCS) += hvcserver.o
obj-$(CONFIG_HCALL_STATS) += hvCall_inst.o
obj-$(CONFIG_PHYP_DUMP) += phyp_dump.o
obj-$(CONFIG_CMM) += cmm.o
+obj-$(CONFIG_DTL) += dtl.o
diff --git a/arch/powerpc/platforms/pseries/dtl.c b/arch/powerpc/platforms/pseries/dtl.c
new file mode 100644
index 0000000..dc9b0f8
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/dtl.c
@@ -0,0 +1,274 @@
+/*
+ * Virtual Processor Dispatch Trace Log
+ *
+ * (C) Copyright IBM Corporation 2009
+ *
+ * Author: Jeremy Kerr <jk at ozlabs.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/init.h>
+#include <linux/debugfs.h>
+#include <asm/smp.h>
+#include <asm/system.h>
+#include <asm/uaccess.h>
+
+#include "plpar_wrappers.h"
+
+/*
+ * Layout of entries in the hypervisor's DTL buffer. Although we don't
+ * actually access the internals of an entry (we only need to know the size),
+ * we might as well define it here for reference.
+ */
+struct dtl_entry {
+ u8 dispatch_reason;
+ u8 preempt_reason;
+ u16 processor_id;
+ u32 enqueue_to_dispatch_time;
+ u32 ready_to_enqueue_time;
+ u32 waiting_to_ready_time;
+ u64 timebase;
+ u64 fault_addr;
+ u64 srr0;
+ u64 srr1;
+};
+
+struct dtl {
+ struct dtl_entry *buf;
+ struct dentry *file;
+ int cpu;
+ int buf_entries;
+ u64 last_idx;
+};
+static DEFINE_PER_CPU(struct dtl, dtl);
+
+/*
+ * Dispatch trace log event mask:
+ * 0x7: 0x1: voluntary virtual processor waits
+ * 0x2: time-slice preempts
+ * 0x4: virtual partition memory page faults
+ */
+static u8 dtl_event_mask = 0x7;
+
+
+/*
+ * Size of per-cpu log buffers. Default is just under 16 pages worth.
+ */
+static int dtl_buf_entries = (16 * 85);
+
+
+static int dtl_enable(struct dtl *dtl)
+{
+ unsigned long addr;
+ int ret, hwcpu;
+
+ /* only allow one reader */
+ if (dtl->buf)
+ return -EBUSY;
+
+ /* we need to store the original allocation size for use during read */
+ dtl->buf_entries = dtl_buf_entries;
+
+ dtl->buf = kmalloc_node(dtl->buf_entries * sizeof(struct dtl_entry),
+ GFP_KERNEL, cpu_to_node(dtl->cpu));
+ if (!dtl->buf) {
+ printk(KERN_WARNING "%s: buffer alloc failed for cpu %d\n",
+ __func__, dtl->cpu);
+ return -ENOMEM;
+ }
+
+ /* Register our dtl buffer with the hypervisor. The HV expects the
+ * buffer size to be passed in the second word of the buffer */
+ ((u32 *)dtl->buf)[1] = dtl->buf_entries * sizeof(struct dtl_entry);
+
+ hwcpu = get_hard_smp_processor_id(dtl->cpu);
+ addr = __pa(dtl->buf);
+ ret = register_dtl(hwcpu, addr);
+ if (ret) {
+ printk(KERN_WARNING "%s: DTL registration for cpu %d (hw %d) "
+ "failed with %d\n", __func__, dtl->cpu, hwcpu, ret);
+ kfree(dtl->buf);
+ return -EIO;
+ }
+
+ /* set our initial buffer indices */
+ dtl->last_idx = lppaca[dtl->cpu].dtl_idx = 0;
+
+ /* enable event logging */
+ lppaca[dtl->cpu].dtl_enable_mask = dtl_event_mask;
+
+ return 0;
+}
+
+static void dtl_disable(struct dtl *dtl)
+{
+ int hwcpu = get_hard_smp_processor_id(dtl->cpu);
+
+ lppaca[dtl->cpu].dtl_enable_mask = 0x0;
+
+ unregister_dtl(hwcpu, __pa(dtl->buf));
+
+ kfree(dtl->buf);
+ dtl->buf = NULL;
+ dtl->buf_entries = 0;
+}
+
+/* file interface */
+
+static int dtl_file_open(struct inode *inode, struct file *filp)
+{
+ struct dtl *dtl = inode->i_private;
+ int rc;
+
+ rc = dtl_enable(dtl);
+ if (rc)
+ return rc;
+
+ filp->private_data = dtl;
+ return 0;
+}
+
+static int dtl_file_release(struct inode *inode, struct file *filp)
+{
+ struct dtl *dtl = inode->i_private;
+ dtl_disable(dtl);
+ return 0;
+}
+
+static ssize_t dtl_file_read(struct file *filp, char __user *buf, size_t len,
+ loff_t *pos)
+{
+ int rc, cur_idx, last_idx, n_read, n_req, read_size;
+ struct dtl *dtl;
+
+ if ((len % sizeof(struct dtl_entry)) != 0)
+ return -EINVAL;
+
+ dtl = filp->private_data;
+
+ /* requested number of entries to read */
+ n_req = len / sizeof(struct dtl_entry);
+
+ /* actual number of entries read */
+ n_read = 0;
+
+ cur_idx = lppaca[dtl->cpu].dtl_idx;
+ last_idx = dtl->last_idx;
+
+ if (cur_idx - last_idx > dtl->buf_entries) {
+ pr_debug("%s: hv buffer overflow for cpu %d, samples lost\n",
+ __func__, dtl->cpu);
+ }
+
+ cur_idx %= dtl->buf_entries;
+ last_idx %= dtl->buf_entries;
+
+ /* read the tail of the buffer if we've wrapped */
+ if (last_idx > cur_idx) {
+ read_size = min(n_req, dtl->buf_entries - last_idx);
+
+ rc = copy_to_user(buf, &dtl->buf[last_idx],
+ read_size * sizeof(struct dtl_entry));
+ if (rc)
+ return -EFAULT;
+
+ last_idx = 0;
+ n_req -= read_size;
+ n_read += read_size;
+ buf += read_size * sizeof(struct dtl_entry);
+ }
+
+ /* .. and now the head */
+ read_size = min(n_req, cur_idx - last_idx);
+ rc = copy_to_user(buf, &dtl->buf[last_idx],
+ read_size * sizeof(struct dtl_entry));
+ if (rc)
+ return -EFAULT;
+
+ n_read += read_size;
+ dtl->last_idx += n_read;
+
+ return n_read * sizeof(struct dtl_entry);
+}
+
+static struct file_operations dtl_fops = {
+ .open = dtl_file_open,
+ .release = dtl_file_release,
+ .read = dtl_file_read,
+ .llseek = no_llseek,
+};
+
+static struct dentry *dtl_dir;
+
+static int dtl_setup_file(struct dtl *dtl)
+{
+ char name[10];
+
+ sprintf(name, "cpu-%d", dtl->cpu);
+
+ dtl->file = debugfs_create_file(name, 0400, dtl_dir, dtl, &dtl_fops);
+ if (!dtl->file)
+ return -ENOMEM;
+
+ return 0;
+}
+
+static int dtl_init(void)
+{
+ struct dentry *event_mask_file, *buf_entries_file;
+ int rc, i;
+
+ if (!firmware_has_feature(FW_FEATURE_SPLPAR))
+ return -ENODEV;
+
+ /* set up common debugfs structure */
+
+ rc = -ENOMEM;
+ dtl_dir = debugfs_create_dir("dtl", powerpc_debugfs_root);
+ if (!dtl_dir) {
+ printk(KERN_WARNING "%s: can't create dtl root dir\n",
+ __func__);
+ goto err;
+ }
+
+ event_mask_file = debugfs_create_x8("dtl_event_mask", 0600,
+ dtl_dir, &dtl_event_mask);
+ buf_entries_file = debugfs_create_u32("dtl_buf_entries", 0600,
+ dtl_dir, &dtl_buf_entries);
+
+ if (!event_mask_file || !buf_entries_file) {
+ printk(KERN_WARNING "%s: can't create dtl files\n", __func__);
+ goto err_remove_dir;
+ }
+
+ /* set up the per-cpu log structures */
+ for_each_possible_cpu(i) {
+ struct dtl *dtl = &per_cpu(dtl, i);
+ dtl->cpu = i;
+
+ rc = dtl_setup_file(dtl);
+ if (rc)
+ goto err_remove_dir;
+ }
+
+ return 0;
+
+err_remove_dir:
+ debugfs_remove_recursive(dtl_dir);
+err:
+ return rc;
+}
+arch_initcall(dtl_init);
diff --git a/arch/powerpc/platforms/pseries/plpar_wrappers.h b/arch/powerpc/platforms/pseries/plpar_wrappers.h
index d967c18..a24a6b2 100644
--- a/arch/powerpc/platforms/pseries/plpar_wrappers.h
+++ b/arch/powerpc/platforms/pseries/plpar_wrappers.h
@@ -43,6 +43,16 @@ static inline long register_slb_shadow(unsigned long cpu, unsigned long vpa)
return vpa_call(0x3, cpu, vpa);
}
+static inline long unregister_dtl(unsigned long cpu, unsigned long vpa)
+{
+ return vpa_call(0x6, cpu, vpa);
+}
+
+static inline long register_dtl(unsigned long cpu, unsigned long vpa)
+{
+ return vpa_call(0x2, cpu, vpa);
+}
+
static inline long plpar_page_set_loaned(unsigned long vpa)
{
unsigned long cmo_page_sz = cmo_get_page_size();
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