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Treat mbufs as cacheline-aligned. Even when the transfer begins at an

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offset within the buffer to align the L3 headers we know the buffer itself
was allocated and sized on cacheline boundaries and we don't need to
preserve partitial cachelines at the start and end of the buffer when
doing busdma sync operations.
This commit is contained in:
ian 2015-10-21 19:24:20 +00:00
parent 9265dcc3a2
commit 492b716bf0
1 changed files with 12 additions and 4 deletions
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16
sys/mips/mips/busdma_machdep.c
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@ -951,6 +951,8 @@ _bus_dmamap_load_buffer(bus_dma_tag_t dmat, bus_dmamap_t map, void *buf,
if (segs == NULL)
segs = dmat->segments;
if ((flags & BUS_DMA_LOAD_MBUF) != 0)
map->flags |= DMAMAP_CACHE_ALIGNED;
if ((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) {
_bus_dmamap_count_pages(dmat, map, pmap, buf, buflen, flags);
@ -1071,10 +1073,16 @@ bus_dmamap_sync_buf(vm_offset_t buf, int len, bus_dmasync_op_t op, int aligned)
* prevent a data loss we save these chunks in temporary buffer
* before invalidation and restore them afer it.
*
* If the aligned flag is set the buffer came from our allocator caches
* which are always sized and aligned to cacheline boundaries, so we can
* skip preserving nearby data if a transfer is unaligned (especially
* it's likely to not end on a boundary).
* If the aligned flag is set the buffer is either an mbuf or came from
* our allocator caches. In both cases they are always sized and
* aligned to cacheline boundaries, so we can skip preserving nearby
* data if a transfer appears to overlap cachelines. An mbuf in
* particular will usually appear to be overlapped because of offsetting
* within the buffer to align the L3 headers, but we know that the bytes
* preceeding that offset are part of the same mbuf memory and are not
* unrelated adjacent data (and a rule of mbuf handling is that the cpu
* is not allowed to touch the mbuf while dma is in progress, including
* header fields).
*/
if (aligned) {
size_cl = 0;