From patchwork Wed Mar 4 23:22:46 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Niklas_S=C3=B6derlund?= X-Patchwork-Id: 2963 Return-Path: Received: from vsp-unauthed02.binero.net (vsp-unauthed02.binero.net [195.74.38.227]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 77CC96285C for ; Thu, 5 Mar 2020 00:23:49 +0100 (CET) X-Halon-ID: 334a5e81-5e6f-11ea-9f85-005056917a89 Authorized-sender: niklas@soderlund.pp.se Received: from bismarck.berto.se (p4fca2392.dip0.t-ipconnect.de [79.202.35.146]) by bin-vsp-out-01.atm.binero.net (Halon) with ESMTPA id 334a5e81-5e6f-11ea-9f85-005056917a89; Thu, 05 Mar 2020 00:23:48 +0100 (CET) From: =?utf-8?q?Niklas_S=C3=B6derlund?= To: libcamera-devel@lists.libcamera.org Date: Thu, 5 Mar 2020 00:22:46 +0100 Message-Id: <20200304232246.325384-8-niklas.soderlund@ragnatech.se> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200304232246.325384-1-niklas.soderlund@ragnatech.se> References: <20200304232246.325384-1-niklas.soderlund@ragnatech.se> MIME-Version: 1.0 Subject: [libcamera-devel] [PATCH v3 7/7] libcamera: V4L2BufferCache: Improve cache eviction strategy X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 04 Mar 2020 23:23:49 -0000 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 numer 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 Reviewed-by: Naushir Patuck Reviewed-by: Laurent Pinchart --- * Changes since v2 - Use a sequence number instead of timestamp to judge age of a cached entry. --- src/libcamera/include/v4l2_videodevice.h | 5 ++++- src/libcamera/v4l2_videodevice.cpp | 20 ++++++++++++-------- 2 files changed, 16 insertions(+), 9 deletions(-) diff --git a/src/libcamera/include/v4l2_videodevice.h b/src/libcamera/include/v4l2_videodevice.h index 359b366454e4e782..993ebb3069c595bf 100644 --- a/src/libcamera/include/v4l2_videodevice.h +++ b/src/libcamera/include/v4l2_videodevice.h @@ -10,6 +10,7 @@ #include #include +#include #include #include @@ -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 planes_; }; + std::atomic_uint64_t lastUsedCounter_; std::vector 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 c495de85f26efe14..3043aebfe0588290 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 +176,11 @@ V4L2BufferCache::V4L2BufferCache(unsigned int numEntries) * allocated. */ V4L2BufferCache::V4L2BufferCache(const std::vector> &buffers) - : missCounter_(0) + : lastUsedCounter_(1), missCounter_(0) { for (const std::unique_ptr &buffer : buffers) - cache_.emplace_back(true, buffer->planes()); + cache_.emplace_back(true, lastUsedCounter_.fetch_add(1), + buffer->planes()); } V4L2BufferCache::~V4L2BufferCache() @@ -205,6 +206,7 @@ int V4L2BufferCache::get(const FrameBuffer &buffer) { bool hit = false; int use = -1; + uint64_t oldest = UINT32_MAX; for (unsigned int index = 0; index < cache_.size(); index++) { const Entry &entry = cache_[index]; @@ -219,8 +221,10 @@ int V4L2BufferCache::get(const FrameBuffer &buffer) break; } - if (use < 0) + if (entry.lastUsed < oldest) { use = index; + oldest = entry.lastUsed; + } } if (!hit) @@ -229,7 +233,7 @@ int V4L2BufferCache::get(const FrameBuffer &buffer) if (use < 0) return -ENOENT; - cache_[use] = Entry(false, buffer); + cache_[use] = Entry(false, lastUsedCounter_.fetch_add(1), buffer); return use; } @@ -245,12 +249,12 @@ 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);