Commit-ID: aa319bcd366349c6f72fcd331da89d3d06090651 Gitweb: http://git.kernel.org/tip/aa319bcd366349c6f72fcd331da89d3d06090651 Author: Alexander Shishkin <[email protected]> AuthorDate: Fri, 22 May 2015 18:30:20 +0300 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 27 May 2015 09:16:20 +0200
perf: Disallow sparse AUX allocations for non-SG PMUs in overwrite mode PMUs that don't support hardware scatter tables require big contiguous chunks of memory and a PMI to switch between them. However, in overwrite using a PMI for this purpose adds extra overhead that the users would like to avoid. Thus, in overwrite mode for such PMUs we can only allow one contiguous chunk for the entire requested buffer. This patch changes the behavior accordingly, so that if the buddy allocator fails to come up with a single high-order chunk for the entire requested buffer, the allocation will fail. Signed-off-by: Alexander Shishkin <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/1432308626-18845-2-git-send-email-alexander.shish...@linux.intel.com Signed-off-by: Ingo Molnar <[email protected]> --- kernel/events/ring_buffer.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 232f00f..725c416 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -493,6 +493,20 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, rb->aux_pages[rb->aux_nr_pages] = page_address(page++); } + /* + * In overwrite mode, PMUs that don't support SG may not handle more + * than one contiguous allocation, since they rely on PMI to do double + * buffering. In this case, the entire buffer has to be one contiguous + * chunk. + */ + if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) && + overwrite) { + struct page *page = virt_to_page(rb->aux_pages[0]); + + if (page_private(page) != max_order) + goto out; + } + rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages, overwrite); if (!rb->aux_priv) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
