summaryrefslogtreecommitdiff
path: root/src
diff options
context:
space:
mode:
authorNiklas Söderlund <niklas.soderlund@ragnatech.se>2020-02-16 16:51:53 +0100
committerNiklas Söderlund <niklas.soderlund@ragnatech.se>2020-03-06 17:45:48 +0100
commit4e0d1eca10b7d2cf0ccbdbebee698d6b716d075b (patch)
tree099a879c4532b871351bded5e07b142a318d5e73 /src
parent69d1e24ac75dc4003737b926bee3ce05420d047b (diff)
libcamera: V4L2BufferCache: Improve cache eviction strategy
The strategy used to find a free cache entry in the first implementation was not the smartest, it picked the first free entry. This lead to unwanted performance issues as the cache was not used as good as it could for imported buffers. Improve this by adding a last usage sequence number to the cache entries and change the eviction strategy to use the oldest free entry instead of the first one it finds. Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Naushir Patuck <naush@raspberrypi.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Diffstat (limited to 'src')
-rw-r--r--src/libcamera/include/v4l2_videodevice.h7
-rw-r--r--src/libcamera/v4l2_videodevice.cpp23
2 files changed, 20 insertions, 10 deletions
diff --git a/src/libcamera/include/v4l2_videodevice.h b/src/libcamera/include/v4l2_videodevice.h
index 359b3664..04802012 100644
--- a/src/libcamera/include/v4l2_videodevice.h
+++ b/src/libcamera/include/v4l2_videodevice.h
@@ -7,11 +7,12 @@
#ifndef __LIBCAMERA_V4L2_VIDEODEVICE_H__
#define __LIBCAMERA_V4L2_VIDEODEVICE_H__
+#include <atomic>
+#include <memory>
#include <string>
#include <vector>
#include <linux/videodev2.h>
-#include <memory>
#include <libcamera/buffer.h>
#include <libcamera/geometry.h>
@@ -120,11 +121,12 @@ private:
{
public:
Entry();
- Entry(bool free, const FrameBuffer &buffer);
+ Entry(bool free, uint64_t lastUsed, const FrameBuffer &buffer);
bool operator==(const FrameBuffer &buffer) const;
bool free;
+ uint64_t lastUsed;
private:
struct Plane {
@@ -140,6 +142,7 @@ private:
std::vector<Plane> planes_;
};
+ std::atomic_uint64_t lastUsedCounter_;
std::vector<Entry> cache_;
/* \todo Expose the miss counter through an instrumentation API. */
unsigned int missCounter_;
diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
index c495de85..ca0d147f 100644
--- a/src/libcamera/v4l2_videodevice.cpp
+++ b/src/libcamera/v4l2_videodevice.cpp
@@ -162,7 +162,7 @@ LOG_DECLARE_CATEGORY(V4L2)
* buffer import, with buffers added to the cache as they are queued.
*/
V4L2BufferCache::V4L2BufferCache(unsigned int numEntries)
- : missCounter_(0)
+ : lastUsedCounter_(1), missCounter_(0)
{
cache_.resize(numEntries);
}
@@ -176,10 +176,12 @@ V4L2BufferCache::V4L2BufferCache(unsigned int numEntries)
* allocated.
*/
V4L2BufferCache::V4L2BufferCache(const std::vector<std::unique_ptr<FrameBuffer>> &buffers)
- : missCounter_(0)
+ : lastUsedCounter_(1), missCounter_(0)
{
for (const std::unique_ptr<FrameBuffer> &buffer : buffers)
- cache_.emplace_back(true, buffer->planes());
+ cache_.emplace_back(true,
+ lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
+ buffer->planes());
}
V4L2BufferCache::~V4L2BufferCache()
@@ -205,6 +207,7 @@ int V4L2BufferCache::get(const FrameBuffer &buffer)
{
bool hit = false;
int use = -1;
+ uint64_t oldest = UINT64_MAX;
for (unsigned int index = 0; index < cache_.size(); index++) {
const Entry &entry = cache_[index];
@@ -219,8 +222,10 @@ int V4L2BufferCache::get(const FrameBuffer &buffer)
break;
}
- if (use < 0)
+ if (entry.lastUsed < oldest) {
use = index;
+ oldest = entry.lastUsed;
+ }
}
if (!hit)
@@ -229,7 +234,9 @@ int V4L2BufferCache::get(const FrameBuffer &buffer)
if (use < 0)
return -ENOENT;
- cache_[use] = Entry(false, buffer);
+ cache_[use] = Entry(false,
+ lastUsedCounter_.fetch_add(1, std::memory_order_acq_rel),
+ buffer);
return use;
}
@@ -245,12 +252,12 @@ void V4L2BufferCache::put(unsigned int index)
}
V4L2BufferCache::Entry::Entry()
- : free(true)
+ : free(true), lastUsed(0)
{
}
-V4L2BufferCache::Entry::Entry(bool free, const FrameBuffer &buffer)
- : free(free)
+V4L2BufferCache::Entry::Entry(bool free, uint64_t lastUsed, const FrameBuffer &buffer)
+ : free(free), lastUsed(lastUsed)
{
for (const FrameBuffer::Plane &plane : buffer.planes())
planes_.emplace_back(plane);