From: Changbin Du <changbin...@intel.com>
The default NR_CPUS can be very large, but actual possible nr_cpu_ids
usually is very small. For my x86 distribution, the NR_CPUS is 8192 and
nr_cpu_ids is 4. About 2 pages are wasted.
Most machines don't have so many CPUs, so define a array with NR_CPUS
just wastes memory. So let's allocate the buffer dynamically when need.
Signed-off-by: Changbin Du <changbin...@intel.com>
---
kernel/trace/trace.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 752e5da..d1b3f11 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4184,19 +4184,18 @@ static const struct file_operations show_traces_fops = {
*/
static DEFINE_MUTEX(tracing_cpumask_update_lock);
-/*
- * Temporary storage for the character representation of the
- * CPU bitmask (and one more byte for the newline):
- */
-static char mask_str[NR_CPUS + 1];
-
static ssize_t
tracing_cpumask_read(struct file *filp, char __user *ubuf,
size_t count, loff_t *ppos)
{
struct trace_array *tr = file_inode(filp)->i_private;
+ static char *mask_str;
int len;
+ mask_str = kmalloc(nr_cpu_ids + 1, GFP_KERNEL);
+ if (!mask_str)
+ return -ENOMEM;
+
mutex_lock(&tracing_cpumask_update_lock);
len = snprintf(mask_str, count, "%*pb\n",
@@ -4205,10 +4204,12 @@ tracing_cpumask_read(struct file *filp, char __user
*ubuf,
count = -EINVAL;
goto out_err;
}
- count = simple_read_from_buffer(ubuf, count, ppos, mask_str, NR_CPUS+1);
+ count = simple_read_from_buffer(ubuf, count, ppos,
+ mask_str, nr_cpu_ids+1);
out_err:
mutex_unlock(&tracing_cpumask_update_lock);
+ kfree(mask_str);
return count;
}
--
2.7.4
