[for-next][PATCH 5/7] tracing: Have saved_cmdlines use the seq_read infrastructure
From: Yoshihiro YUNOMAE
Current tracing_saved_cmdlines_read() implementation is naive; It allocates
a large buffer, constructs output data to that buffer for each read
operation, and then copies a portion of the buffer to the user space
buffer. This has several issues such as slow memory allocation, high
CPU usage, and even corruption of the output data.
The seq_read infrastructure is made to handle this type of work.
By converting it to use seq_read() the code becomes smaller, simplified,
as well as correct.
Link: http://lkml.kernel.org/p/20140220084431.3839.51793.stgit@yunodevel
Signed-off-by: Hidehiro Kawai
Cc: Namhyung Kim
Cc: Masami Hiramatsu
Signed-off-by: Yoshihiro YUNOMAE
Cc: Frederic Weisbecker
Cc: Ingo Molnar
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Steven Rostedt
---
kernel/trace/trace.c | 89 +++-
1 file changed, 54 insertions(+), 35 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index eb228b9de170..1855dae73f34 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3699,55 +3699,74 @@ static const struct file_operations tracing_readme_fops
= {
.llseek = generic_file_llseek,
};
-static ssize_t
-tracing_saved_cmdlines_read(struct file *file, char __user *ubuf,
- size_t cnt, loff_t *ppos)
+static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
{
- char *buf_comm;
- char *file_buf;
- char *buf;
- int len = 0;
- int pid;
- int i;
+ unsigned int *ptr = v;
- file_buf = kmalloc(SAVED_CMDLINES*(16+TASK_COMM_LEN), GFP_KERNEL);
- if (!file_buf)
- return -ENOMEM;
+ if (*pos || m->count)
+ ptr++;
- buf_comm = kmalloc(TASK_COMM_LEN, GFP_KERNEL);
- if (!buf_comm) {
- kfree(file_buf);
- return -ENOMEM;
- }
+ (*pos)++;
+
+ for (; ptr < _cmdline_to_pid[SAVED_CMDLINES]; ptr++) {
+ if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
+ continue;
- buf = file_buf;
+ return ptr;
+ }
- for (i = 0; i < SAVED_CMDLINES; i++) {
- int r;
+ return NULL;
+}
- pid = map_cmdline_to_pid[i];
- if (pid == -1 || pid == NO_CMDLINE_MAP)
- continue;
+static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
+{
+ void *v;
+ loff_t l = 0;
- trace_find_cmdline(pid, buf_comm);
- r = sprintf(buf, "%d %s\n", pid, buf_comm);
- buf += r;
- len += r;
+ v = _cmdline_to_pid[0];
+ while (l <= *pos) {
+ v = saved_cmdlines_next(m, v, );
+ if (!v)
+ return NULL;
}
- len = simple_read_from_buffer(ubuf, cnt, ppos,
- file_buf, len);
+ return v;
+}
- kfree(file_buf);
- kfree(buf_comm);
+static void saved_cmdlines_stop(struct seq_file *m, void *v)
+{
+}
- return len;
+static int saved_cmdlines_show(struct seq_file *m, void *v)
+{
+ char buf[TASK_COMM_LEN];
+ unsigned int *pid = v;
+
+ trace_find_cmdline(*pid, buf);
+ seq_printf(m, "%d %s\n", *pid, buf);
+ return 0;
+}
+
+static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
+ .start = saved_cmdlines_start,
+ .next = saved_cmdlines_next,
+ .stop = saved_cmdlines_stop,
+ .show = saved_cmdlines_show,
+};
+
+static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)
+{
+ if (tracing_disabled)
+ return -ENODEV;
+
+ return seq_open(filp, _saved_cmdlines_seq_ops);
}
static const struct file_operations tracing_saved_cmdlines_fops = {
-.open = tracing_open_generic,
-.read = tracing_saved_cmdlines_read,
-.llseek= generic_file_llseek,
+ .open = tracing_saved_cmdlines_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release= seq_release,
};
static ssize_t
--
2.0.0.rc2
--
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[for-next][PATCH 5/7] tracing: Have saved_cmdlines use the seq_read infrastructure
From: Yoshihiro YUNOMAE yoshihiro.yunomae...@hitachi.com
Current tracing_saved_cmdlines_read() implementation is naive; It allocates
a large buffer, constructs output data to that buffer for each read
operation, and then copies a portion of the buffer to the user space
buffer. This has several issues such as slow memory allocation, high
CPU usage, and even corruption of the output data.
The seq_read infrastructure is made to handle this type of work.
By converting it to use seq_read() the code becomes smaller, simplified,
as well as correct.
Link: http://lkml.kernel.org/p/20140220084431.3839.51793.stgit@yunodevel
Signed-off-by: Hidehiro Kawai hidehiro.kawai...@hitachi.com
Cc: Namhyung Kim namhy...@kernel.org
Cc: Masami Hiramatsu masami.hiramatsu...@hitachi.com
Signed-off-by: Yoshihiro YUNOMAE yoshihiro.yunomae...@hitachi.com
Cc: Frederic Weisbecker fweis...@gmail.com
Cc: Ingo Molnar mi...@redhat.com
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Steven Rostedt rost...@goodmis.org
---
kernel/trace/trace.c | 89 +++-
1 file changed, 54 insertions(+), 35 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index eb228b9de170..1855dae73f34 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3699,55 +3699,74 @@ static const struct file_operations tracing_readme_fops
= {
.llseek = generic_file_llseek,
};
-static ssize_t
-tracing_saved_cmdlines_read(struct file *file, char __user *ubuf,
- size_t cnt, loff_t *ppos)
+static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
{
- char *buf_comm;
- char *file_buf;
- char *buf;
- int len = 0;
- int pid;
- int i;
+ unsigned int *ptr = v;
- file_buf = kmalloc(SAVED_CMDLINES*(16+TASK_COMM_LEN), GFP_KERNEL);
- if (!file_buf)
- return -ENOMEM;
+ if (*pos || m-count)
+ ptr++;
- buf_comm = kmalloc(TASK_COMM_LEN, GFP_KERNEL);
- if (!buf_comm) {
- kfree(file_buf);
- return -ENOMEM;
- }
+ (*pos)++;
+
+ for (; ptr map_cmdline_to_pid[SAVED_CMDLINES]; ptr++) {
+ if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
+ continue;
- buf = file_buf;
+ return ptr;
+ }
- for (i = 0; i SAVED_CMDLINES; i++) {
- int r;
+ return NULL;
+}
- pid = map_cmdline_to_pid[i];
- if (pid == -1 || pid == NO_CMDLINE_MAP)
- continue;
+static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
+{
+ void *v;
+ loff_t l = 0;
- trace_find_cmdline(pid, buf_comm);
- r = sprintf(buf, %d %s\n, pid, buf_comm);
- buf += r;
- len += r;
+ v = map_cmdline_to_pid[0];
+ while (l = *pos) {
+ v = saved_cmdlines_next(m, v, l);
+ if (!v)
+ return NULL;
}
- len = simple_read_from_buffer(ubuf, cnt, ppos,
- file_buf, len);
+ return v;
+}
- kfree(file_buf);
- kfree(buf_comm);
+static void saved_cmdlines_stop(struct seq_file *m, void *v)
+{
+}
- return len;
+static int saved_cmdlines_show(struct seq_file *m, void *v)
+{
+ char buf[TASK_COMM_LEN];
+ unsigned int *pid = v;
+
+ trace_find_cmdline(*pid, buf);
+ seq_printf(m, %d %s\n, *pid, buf);
+ return 0;
+}
+
+static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
+ .start = saved_cmdlines_start,
+ .next = saved_cmdlines_next,
+ .stop = saved_cmdlines_stop,
+ .show = saved_cmdlines_show,
+};
+
+static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)
+{
+ if (tracing_disabled)
+ return -ENODEV;
+
+ return seq_open(filp, tracing_saved_cmdlines_seq_ops);
}
static const struct file_operations tracing_saved_cmdlines_fops = {
-.open = tracing_open_generic,
-.read = tracing_saved_cmdlines_read,
-.llseek= generic_file_llseek,
+ .open = tracing_saved_cmdlines_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release= seq_release,
};
static ssize_t
--
2.0.0.rc2
--
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