Re: [PATCH 6/9] xfs: consolidate btree block freeing tracepoints

Darrick J. Wong
2024-01-03T19:37:06Z

On Wed, Jan 03, 2024 at 12:53:17AM -0800, Christoph Hellwig wrote:
> On Sun, Dec 31, 2023 at 12:15:07PM -0800, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> >
> > Don't waste tracepoint segment memory on per-btree block freeing
> > tracepoints when we can do it from the generic btree code.
>
> The patch looks good, but what is "tracepoint segment memory"?

The size of the ELF segments where the ftrace strings/code/etc are
stored. With this and the next patch applied, the output of:

$ objdump -x fs/xfs/xfs.ko | grep tracepoint

Before:

10 __tracepoints_ptrs 00000b38 0000000000000000 0000000000000000 001418b0 2**2
14 __tracepoints_strings 00005433 0000000000000000 0000000000000000 00168f60 2**5
29 __tracepoints 00010d30 0000000000000000 0000000000000000 00240080 2**5

After:

10 __tracepoints_ptrs 00000b30 0000000000000000 0000000000000000 00142170 2**2
14 __tracepoints_strings 000053f3 0000000000000000 0000000000000000 00169860 2**5
29 __tracepoints 00010c70 0000000000000000 0000000000000000 00241180 2**5

Removing these two tracepoints reduces the size of the ELF segments by
264 bytes. I'll add this note to the commit message.

--D