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.
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| @@ -493,6 +493,20 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, · 492 unmodified lines | |||
| 493 | rb->aux_pages[rb->aux_nr_pages] = page_address(page++); | 493 | rb->aux_pages[rb->aux_nr_pages] = page_address(page++); |
| 494 | } | 494 | } |
| 495 | 495 | ||
| 496 | /* | ||
| 497 | * In overwrite mode, PMUs that don't support SG may not handle more | ||
| 498 | * than one contiguous allocation, since they rely on PMI to do double | ||
| 499 | * buffering. In this case, the entire buffer has to be one contiguous | ||
| 500 | * chunk. | ||
| 501 | */ | ||
| 502 | if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) && | ||
| 503 | overwrite) { | ||
| 504 | struct page *page = virt_to_page(rb->aux_pages[0]); | ||
| 505 | |||
| 506 | if (page_private(page) != max_order) | ||
| 507 | goto out; | ||
| 508 | } | ||
| 509 | |||
| 496 | rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages, | 510 | rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages, |
| 497 | overwrite); | 511 | overwrite); |
| 498 | if (!rb->aux_priv) | 512 | if (!rb->aux_priv) |