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tracing/events: Add bounce tracing to swiotbl

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Ftrace is currently not able to detect when SWIOTLB has to do double buffering.
Under Xen you can only see it indirectly in function_graph, when
xen_swiotlb_map_page() doesn't stop after range_straddles_page_boundary(), but
calls spinlock functions, memcpy() and xen_phys_to_bus() as well. This patch
introduces the swiotlb:swiotlb_bounced event, which also prints out the
following informations to help you find out why bouncing happened:

dev_name: 0000:08:00.0 dma_mask=ffffffffffffffff dev_addr=9149f000 size=32768
swiotlb_force=0

If you use Xen, and (dev_addr + size + 1) > dma_mask, the buffer is out of the
device's DMA range. If swiotlb_force == 1, you should really change the kernel
parameters. Otherwise, the buffer is not contiguous in mfn space.

Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
[v1: Don't print 'swiotlb_force=X', just print swiotlb_force if it is enabled]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
Zoltan Kiss 2013-09-04 21:11:05 +01:00 committed by Konrad Rzeszutek Wilk
parent 04b772d2b8
commit 2b2b614dd2
3 changed files with 55 additions and 0 deletions
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5
drivers/xen/swiotlb-xen.c
View File

@ -42,6 +42,9 @@
#include <xen/page.h>
#include <xen/xen-ops.h>
#include <xen/hvc-console.h>
#define CREATE_TRACE_POINTS
#include <trace/events/swiotlb.h>
/*
* Used to do a quick range check in swiotlb_tbl_unmap_single and
* swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
@ -358,6 +361,8 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
/*
* Oh well, have to allocate and map a bounce buffer.
*/
trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);
map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir);
if (map == SWIOTLB_MAP_ERROR)
return DMA_ERROR_CODE;

46
include/trace/events/swiotlb.h Normal file
View File

@ -0,0 +1,46 @@
#undef TRACE_SYSTEM
#define TRACE_SYSTEM swiotlb
#if !defined(_TRACE_SWIOTLB_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_SWIOTLB_H
#include <linux/tracepoint.h>
TRACE_EVENT(swiotlb_bounced,
TP_PROTO(struct device *dev,
dma_addr_t dev_addr,
size_t size,
int swiotlb_force),
TP_ARGS(dev, dev_addr, size, swiotlb_force),
TP_STRUCT__entry(
__string( dev_name, dev_name(dev) )
__field( u64, dma_mask )
__field( dma_addr_t, dev_addr )
__field( size_t, size )
__field( int, swiotlb_force )
),
TP_fast_assign(
__assign_str(dev_name, dev_name(dev));
__entry->dma_mask = (dev->dma_mask ? *dev->dma_mask : 0);
__entry->dev_addr = dev_addr;
__entry->size = size;
__entry->swiotlb_force = swiotlb_force;
),
TP_printk("dev_name: %s dma_mask=%llx dev_addr=%llx "
"size=%zu %s",
__get_str(dev_name),
__entry->dma_mask,
(unsigned long long)__entry->dev_addr,
__entry->size,
__entry->swiotlb_force ? "swiotlb_force" : "" )
);
#endif /* _TRACE_SWIOTLB_H */
/* This part must be outside protection */
#include <trace/define_trace.h>

4
lib/swiotlb.c
View File

@ -38,6 +38,8 @@
#include <linux/bootmem.h>
#include <linux/iommu-helper.h>
#include <trace/events/swiotlb.h>
#define OFFSET(val,align) ((unsigned long) \
( (val) & ( (align) - 1)))
@ -726,6 +728,8 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
if (dma_capable(dev, dev_addr, size) && !swiotlb_force)
return dev_addr;
trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);
/* Oh well, have to allocate and map a bounce buffer. */
map = map_single(dev, phys, size, dir);
if (map == SWIOTLB_MAP_ERROR) {