From: "Steven Rostedt (Google)" <[email protected]>
The saved_cmdlines have three arrays for mapping PIDs to COMMs:
- map_pid_to_cmdline[]
- map_cmdline_to_pid[]
- saved_cmdlines
The map_pid_to_cmdline[] is PID_MAX_DEFAULT in size and holds the index
into the other arrays. The map_cmdline_to_pid[] is a mapping back to the
full pid as it can be larger than PID_MAX_DEFAULT. And the
saved_cmdlines[] just holds the COMMs associated to the pids.
Currently the map_pid_to_cmdline[] and saved_cmdlines[] are allocated
together (in reality the saved_cmdlines is just in the memory of the
rounding of the allocation of the structure as it is always allocated in
powers of two). The map_cmdline_to_pid[] array is allocated separately.
Since the rounding to a power of two is rather large (it allows for 8000
elements in saved_cmdlines), also include the map_cmdline_to_pid[] array.
(This drops it to 6000 by default, which is still plenty for most use
cases). This saves even more memory as the map_cmdline_to_pid[] array
doesn't need to be allocated.
Link: https://lore.kernel.org/linux-trace-kernel/[email protected]/
Signed-off-by: Steven Rostedt (Google) <[email protected]>
---
Changes since v1: https://lore.kernel.org/linux-trace-kernel/[email protected]/
-- Added SAVED_CMDLINE_MAP_ELEMENT_SIZE helper macro.
kernel/trace/trace_sched_switch.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index e4fbcc3bede5..5f3e9bc87079 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -175,6 +175,10 @@ struct saved_cmdlines_buffer {
};
static struct saved_cmdlines_buffer *savedcmd;
+/* Holds the size of a cmdline and pid element */
+#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \
+ (TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))
+
static inline char *get_saved_cmdlines(int idx)
{
return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
@@ -201,7 +205,7 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
int order;
/* Figure out how much is needed to hold the given number of cmdlines */
- orig_size = sizeof(*s) + val * TASK_COMM_LEN;
+ orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
order = get_order(orig_size);
size = 1 << (order + PAGE_SHIFT);
page = alloc_pages(GFP_KERNEL, order);
@@ -212,16 +216,11 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
memset(s, 0, sizeof(*s));
/* Round up to actual allocation */
- val = (size - sizeof(*s)) / TASK_COMM_LEN;
+ val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
s->cmdline_num = val;
- s->map_cmdline_to_pid = kmalloc_array(val,
- sizeof(*s->map_cmdline_to_pid),
- GFP_KERNEL);
- if (!s->map_cmdline_to_pid) {
- free_saved_cmdlines_buffer(s);
- return NULL;
- }
+ /* Place map_cmdline_to_pid array right after saved_cmdlines */
+ s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];
s->cmdline_idx = 0;
memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
--
2.43.0
On Tue, 13 Feb 2024 11:52:32 -0500
Steven Rostedt <[email protected]> wrote:
> From: "Steven Rostedt (Google)" <[email protected]>
>
> The saved_cmdlines have three arrays for mapping PIDs to COMMs:
>
> - map_pid_to_cmdline[]
> - map_cmdline_to_pid[]
> - saved_cmdlines
>
> The map_pid_to_cmdline[] is PID_MAX_DEFAULT in size and holds the index
> into the other arrays. The map_cmdline_to_pid[] is a mapping back to the
> full pid as it can be larger than PID_MAX_DEFAULT. And the
> saved_cmdlines[] just holds the COMMs associated to the pids.
>
> Currently the map_pid_to_cmdline[] and saved_cmdlines[] are allocated
> together (in reality the saved_cmdlines is just in the memory of the
> rounding of the allocation of the structure as it is always allocated in
> powers of two). The map_cmdline_to_pid[] array is allocated separately.
>
> Since the rounding to a power of two is rather large (it allows for 8000
> elements in saved_cmdlines), also include the map_cmdline_to_pid[] array.
> (This drops it to 6000 by default, which is still plenty for most use
> cases). This saves even more memory as the map_cmdline_to_pid[] array
> doesn't need to be allocated.
>
> Link: https://lore.kernel.org/linux-trace-kernel/[email protected]/
>
OK, this looks good to me.
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Thank you,
> Signed-off-by: Steven Rostedt (Google) <[email protected]>
> ---
> Changes since v1: https://lore.kernel.org/linux-trace-kernel/[email protected]/
>
> -- Added SAVED_CMDLINE_MAP_ELEMENT_SIZE helper macro.
>
> kernel/trace/trace_sched_switch.c | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
> index e4fbcc3bede5..5f3e9bc87079 100644
> --- a/kernel/trace/trace_sched_switch.c
> +++ b/kernel/trace/trace_sched_switch.c
> @@ -175,6 +175,10 @@ struct saved_cmdlines_buffer {
> };
> static struct saved_cmdlines_buffer *savedcmd;
>
> +/* Holds the size of a cmdline and pid element */
> +#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \
> + (TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))
> +
> static inline char *get_saved_cmdlines(int idx)
> {
> return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
> @@ -201,7 +205,7 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
> int order;
>
> /* Figure out how much is needed to hold the given number of cmdlines */
> - orig_size = sizeof(*s) + val * TASK_COMM_LEN;
> + orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
> order = get_order(orig_size);
> size = 1 << (order + PAGE_SHIFT);
> page = alloc_pages(GFP_KERNEL, order);
> @@ -212,16 +216,11 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
> memset(s, 0, sizeof(*s));
>
> /* Round up to actual allocation */
> - val = (size - sizeof(*s)) / TASK_COMM_LEN;
> + val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
> s->cmdline_num = val;
>
> - s->map_cmdline_to_pid = kmalloc_array(val,
> - sizeof(*s->map_cmdline_to_pid),
> - GFP_KERNEL);
> - if (!s->map_cmdline_to_pid) {
> - free_saved_cmdlines_buffer(s);
> - return NULL;
> - }
> + /* Place map_cmdline_to_pid array right after saved_cmdlines */
> + s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];
>
> s->cmdline_idx = 0;
> memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
> --
> 2.43.0
>
>
--
Masami Hiramatsu (Google) <[email protected]>
On Tue, 2024-02-13 at 11:52 -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <[email protected]>
>
> The saved_cmdlines have three arrays for mapping PIDs to COMMs:
>
> - map_pid_to_cmdline[]
> - map_cmdline_to_pid[]
> - saved_cmdlines
>
> The map_pid_to_cmdline[] is PID_MAX_DEFAULT in size and holds the index
> into the other arrays. The map_cmdline_to_pid[] is a mapping back to the
> full pid as it can be larger than PID_MAX_DEFAULT. And the
> saved_cmdlines[] just holds the COMMs associated to the pids.
>
> Currently the map_pid_to_cmdline[] and saved_cmdlines[] are allocated
> together (in reality the saved_cmdlines is just in the memory of the
> rounding of the allocation of the structure as it is always allocated in
> powers of two). The map_cmdline_to_pid[] array is allocated separately.
>
> Since the rounding to a power of two is rather large (it allows for 8000
> elements in saved_cmdlines), also include the map_cmdline_to_pid[] array.
> (This drops it to 6000 by default, which is still plenty for most use
> cases). This saves even more memory as the map_cmdline_to_pid[] array
> doesn't need to be allocated.
>
> Link: https://lore.kernel.org/linux-trace-kernel/[email protected]/
>
> Signed-off-by: Steven Rostedt (Google) <[email protected]>
Patch looks good to me.
Reviewd-by: Tim Chen <[email protected]>
> ---
> Changes since v1: https://lore.kernel.org/linux-trace-kernel/[email protected]/
>
> -- Added SAVED_CMDLINE_MAP_ELEMENT_SIZE helper macro.
>