kernel_optimize_test/include
Steven Rostedt b000c8065a tracing: Remove the extra 4 bytes of padding in events
Due to a userspace issue with PowerTop v2beta, which hardcoded
the offset of event fields that it was using, it broke when
we removed the Big Kernel Lock counter from the event header.

 (commit e6e1e2593 "tracing: Remove lock_depth from event entry")

Because this broke userspace, it was determined that we must
keep those 4 bytes around.

 (commit a3a4a5acd "Regression: partial revert "tracing: Remove lock_depth from event entry"")

This unfortunately wastes space in the ring buffer. 4 bytes per
event, where a lot of events are just 24 bytes. That's 16% of the
buffer wasted. A million events will add 4 megs of white space
into the buffer.

It was later noticed that PowerTop v2beta could not work on systems
where the kernel was 64 bit but the userspace was 32 bits.
The reason was because the offsets are different between the
two and the hard coded offset of one would not work with the other.

With PowerTop v2 final, it implemented the same interface that both
perf and trace-cmd use. That is, it reads the format file of
the event to find the offsets of the fields it needs. This fixes
the problem with running powertop on a 32 bit userspace running
on a 64 bit kernel. It also no longer requires the 4 byte padding.

As PowerTop v2 has been out for a while, and is included in all
major distributions, it is time that we can safely remove the
4 bytes of padding. Users of PowerTop v2beta should upgrade to
PowerTop v2 final.

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2013-01-21 21:05:41 -05:00
..
acpi PCI changes for the v3.8 merge window: 2012-12-13 12:14:47 -08:00
asm-generic mm: limit mmu_gather batching to fix soft lockups on !CONFIG_PREEMPT 2013-01-04 16:11:46 -08:00
clocksource
crypto crypto: cast5/cast6 - move lookup tables to shared module 2012-12-06 17:16:26 +08:00
drm Merge branch 'drm-intel-fixes' of git://people.freedesktop.org/~danvet/drm-intel 2013-01-11 07:52:48 +10:00
keys
linux tracing: Remove the extra 4 bytes of padding in events 2013-01-21 21:05:41 -05:00
math-emu
media
memory
misc
net Merge branch 'master' of git://1984.lsi.us.es/nf 2012-12-28 14:28:17 -08:00
pcmcia
ras
rdma UAPI: Remove empty Kbuild files 2013-01-02 17:36:10 -08:00
rxrpc
scsi SCSI misc on 20121212 2012-12-13 19:20:31 -08:00
sound Merge remote-tracking branch 'asoc/fix/cs4271' into tmp 2013-01-10 12:22:11 +00:00
target target: Introduce TCM_NO_SENSE 2013-01-10 20:06:08 -08:00
trace Various bug fixes for ext4. Perhaps the most serious bug fixed is one 2013-01-02 09:57:34 -08:00
uapi linux/audit.h: move ptrace.h include to kernel header 2013-01-11 14:54:56 -08:00
video Merge branch 'omap-for-v3.8/fixes-for-merge-window' into omap-for-v3.8/fixes-for-merge-window-v2 2012-12-16 11:28:10 -08:00
xen Bugfixes: 2012-12-18 12:26:54 -08:00
Kbuild UAPI: Remove empty Kbuild files 2013-01-02 17:36:10 -08:00