Re: [RFC PATCH v4] Unified trace buffer

From: Masami Hiramatsu
Date: Thu Sep 25 2008 - 21:54:32 EST


Hi Steven,

Steven Rostedt wrote:
This version has been cleaned up a bit. I've been running it as
a back end to ftrace, and it has been handling pretty well.

Thank you for your great work.
It seems good to me(especially, encapsulating events :)).

I have one request of enhancement.

> +static struct ring_buffer_per_cpu *
> +ring_buffer_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
> +{
[...]
> + cpu_buffer->pages = kzalloc_node(ALIGN(sizeof(void *) * pages,
> + cache_line_size()), GFP_KERNEL,
> + cpu_to_node(cpu));

Here, you are using a slab object for page managing array,
the largest object size is 128KB(x86-64), so it can contain
16K pages = 64MB.

As I had improved relayfs, in some rare case(on 64bit arch),
we'd like to use larger buffer than 64MB.

http://sourceware.org/ml/systemtap/2008-q2/msg00103.html

So, I think similar hack can be applicable.

Would it be acceptable for the next version?

Thank you,

--
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@xxxxxxxxxx

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