]> git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/commit
perf/ring_buffer: Use high order allocations for AUX buffers optimistically
authorAlexander Shishkin <alexander.shishkin@linux.intel.com>
Fri, 15 Feb 2019 11:47:27 +0000 (13:47 +0200)
committerIngo Molnar <mingo@kernel.org>
Sat, 9 Mar 2019 13:10:30 +0000 (14:10 +0100)
commit5768402fd9c6e872252b5268ad85e3fbae4fe26b
tree62874f0d5f2b186b16cf50b2d66f24c1e48a3436
parent6ea98b4baa1c9089d7a035ebccb993e03d1ac57f
perf/ring_buffer: Use high order allocations for AUX buffers optimistically

Currently, the AUX buffer allocator will use high-order allocations
for PMUs that don't support hardware scatter-gather chaining to ensure
large contiguous blocks of pages, and always use an array of single
pages otherwise.

There is, however, a tangible performance benefit in using larger chunks
of contiguous memory even in the latter case, that comes from not having
to fetch the next page's address at every page boundary. In particular,
a task running under Intel PT on an Atom CPU shows 1.5%-2% less runtime
penalty with a single multi-page output region in snapshot mode (no PMI)
than with multiple single-page output regions, from ~6% down to ~4%. For
the snapshot mode it does make a difference as it is intended to run over
long periods of time.

For this reason, change the allocation policy to always optimistically
start with the highest possible order when allocating pages for the AUX
buffer, desceding until the allocation succeeds or order zero allocation
fails.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lkml.kernel.org/r/20190215114727.62648-2-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/events/ring_buffer.c