From patchwork Sun Feb 16 16:16:41 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: 2836 Return-Path: Received: from vsp-unauthed02.binero.net (vsp-unauthed02.binero.net [195.74.38.227]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 632DE60438 for ; Sun, 16 Feb 2020 17:17:34 +0100 (CET) X-Halon-ID: d64c5259-50d7-11ea-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 d64c5259-50d7-11ea-9f85-005056917a89; Sun, 16 Feb 2020 17:17:33 +0100 (CET) From: =?utf-8?q?Niklas_S=C3=B6derlund?= To: libcamera-devel@lists.libcamera.org Date: Sun, 16 Feb 2020 17:16:41 +0100 Message-Id: <20200216161642.152263-2-niklas.soderlund@ragnatech.se> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200216161642.152263-1-niklas.soderlund@ragnatech.se> References: <20200216161642.152263-1-niklas.soderlund@ragnatech.se> MIME-Version: 1.0 Subject: [libcamera-devel] [PATCH 1/2] 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: Sun, 16 Feb 2020 16:17:34 -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 they cache was not used as good as it could for imported buffers. Improve this by adding a last usage timestamp 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 --- src/libcamera/include/v4l2_videodevice.h | 1 + src/libcamera/v4l2_videodevice.cpp | 9 ++++++--- 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/src/libcamera/include/v4l2_videodevice.h b/src/libcamera/include/v4l2_videodevice.h index fcf072641420dacf..f04feed87b24f28f 100644 --- a/src/libcamera/include/v4l2_videodevice.h +++ b/src/libcamera/include/v4l2_videodevice.h @@ -125,6 +125,7 @@ private: bool operator==(const FrameBuffer &buffer); bool free; + utils::time_point lastUsed; private: struct Plane { diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp index 99470ce11421c77c..9a4d2479b20f5e27 100644 --- a/src/libcamera/v4l2_videodevice.cpp +++ b/src/libcamera/v4l2_videodevice.cpp @@ -205,6 +205,7 @@ int V4L2BufferCache::get(const FrameBuffer &buffer) { bool hit = false; int use = -1; + utils::time_point oldest = utils::clock::now(); for (unsigned int index = 0; index < cache_.size(); index++) { const Entry &entry = cache_[index]; @@ -212,8 +213,10 @@ int V4L2BufferCache::get(const FrameBuffer &buffer) if (!entry.free) continue; - if (use < 0) + if (cache_[index].lastUsed < oldest) { use = index; + oldest = cache_[index].lastUsed; + } /* Try to find a cache hit by comparing the planes. */ if (cache_[index] == buffer) { @@ -245,12 +248,12 @@ void V4L2BufferCache::put(unsigned int index) } V4L2BufferCache::Entry::Entry() - : free(true) + : free(true), lastUsed(utils::clock::now()) { } V4L2BufferCache::Entry::Entry(bool free, const FrameBuffer &buffer) - : free(free) + : free(free), lastUsed(utils::clock::now()) { for (const FrameBuffer::Plane &plane : buffer.planes()) planes_.emplace_back(plane);