benchmark has no specifications so won't be run by default

spec/unit/benchmark.lua

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+require "defaults"
+package.path = "?.lua;common/?.lua;frontend/?.lua"
+package.cpath = "?.so;common/?.so;/usr/lib/lua/?.so"
+
+-- global einkfb for Screen
+einkfb = require("ffi/framebuffer")
+-- do not show SDL window
+einkfb.dummy = true
+Blitbuffer = require("ffi/blitbuffer")
+
+local Screen = require("ui/screen")
+local DocSettings = require("docsettings")
+G_reader_settings = DocSettings:open(".reader")
+local DocumentRegistry = require("document/documentregistry")
+local util = require("ffi/util")
+local DEBUG = require("dbg")
+
+-- screen should be inited for crengine
+Screen:init()
+
+function logDuration(filename, pageno, dur)
+    local file = io.open(filename, "a+")
+    if file then
+        if file:seek("end") == 0 then -- write the header only once
+            file:write("PAGE\tDUR\n")
+        end
+        file:write(string.format("%s\t%s\n", pageno, dur))
+        file:close()
+    end
+end
+
+describe("PDF rendering benchmark", function()
+    local sample_pdf = "spec/front/unit/data/sample.pdf"
+    local doc = DocumentRegistry:openDocument(sample_pdf)
+    for pageno = 1, math.min(10, doc.info.number_of_pages) do
+        local secs, usecs = util.gettime()
+        assert.truthy(doc:renderPage(pageno, nil, 1, 0, 1.0, 0))
+        local nsecs, nusecs = util.gettime()
+        local dur = nsecs - secs + (nusecs - usecs) / 1000000
+        logDuration("pdf_rendering.log", pageno, dur)
+    end
+    doc:close()
+end)
+
+describe("PDF reflowing benchmark", function()
+    local sample_pdf = "spec/front/unit/data/sample.pdf"
+    local doc = DocumentRegistry:openDocument(sample_pdf)
+    doc.configurable.text_wrap = 1
+    for pageno = 1, math.min(10, doc.info.number_of_pages) do
+        local secs, usecs = util.gettime()
+        assert.truthy(doc:renderPage(pageno, nil, 1, 0, 1.0, 0))
+        local nsecs, nusecs = util.gettime()
+        local dur = nsecs - secs + (nusecs - usecs) / 1000000
+        logDuration("pdf_reflowing.log", pageno, dur)
+    end
+    doc:close()
+end)
+