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Attempt to further reduce re-parsing for globally cached images (PR 11912, 16108 follow-up)

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In PR 11912 we started caching images that occur on multiple pages globally, which improved performance a lot in many PDF documents.
However, one slightly annoying limitation of the implementation is the need to re-parse the image once the global-caching threshold has been reached. Previously this was difficult to avoid, since large image-resources will cause cleanup to run on the main-thread after rendering has finished. In PR 16108 we started delaying this cleanup a little bit, to improve performance if a user e.g. zooms and/or rotates the document immediately after rendering completes.

Taking those two PRs together, we now have a situation where it's much more likely that the main-thread has "globally used" images cached at the page-level. Hence we can instead attempt to *copy* a locally cached image into the global object-cache on the main-thread and thus reduce unnecessary re-parsing of large/complex global images, which significantly reduces the rendering time in many cases.

For the PDF document in issue 11878, the rendering time of *the second page* changes as follows (on my computer):
 - With the `master`-branch it takes >600 ms to render.
 - With this patch that goes down to ~50 ms, which is one order of magnitude faster.

(Note that all other pages are, as expected, completely unaffected by these changes.)

This new main-thread copying is limited to "large" global images, since:
 - Re-parsing of small images, on the worker-thread, is usually fast enough to not be an issue.
 - With the delayed cleanup after rendering, it's still not guaranteed that an image is available in a page-level cache on the main-thread.
 - This forces the worker-thread to wait for the main-thread, which is a pattern that you always want to avoid unless absolutely necessary.
This commit is contained in:
Jonas Jenwald 2023-12-14 21:57:48 +01:00
parent e547b198a3
commit 9f02cc36d4
3 changed files with 95 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
src/core/evaluator.js
View File

@ -771,13 +771,15 @@ class PartialEvaluator {
if (this.parsingType3Font) {
objId = `${this.idFactory.getDocId()}_type3_${objId}`;
} else if (imageRef) {
} else if (cacheKey && imageRef) {
cacheGlobally = this.globalImageCache.shouldCache(
imageRef,
this.pageIndex
);
if (cacheGlobally) {
assert(!isInline, "Cannot cache an inline image globally.");
objId = `${this.idFactory.getDocId()}_${objId}`;
}
}
@ -785,6 +787,30 @@ class PartialEvaluator {
// Ensure that the dependency is added before the image is decoded.
operatorList.addDependency(objId);
args = [objId, w, h];
operatorList.addImageOps(OPS.paintImageXObject, args, optionalContent);
// For large images, at least 500x500 in size, that we'll cache globally
// check if the image is still cached locally on the main-thread to avoid
// having to re-parse the image (since that can be slow).
if (cacheGlobally && w * h > 250000) {
const localLength = await this.handler.sendWithPromise("commonobj", [
objId,
"CopyLocalImage",
{ imageRef },
]);
if (localLength) {
this.globalImageCache.setData(imageRef, {
objId,
fn: OPS.paintImageXObject,
args,
optionalContent,
byteSize: 0, // Temporary entry, to avoid `setData` returning early.
});
this.globalImageCache.addByteSize(imageRef, localLength);
return;
}
}
PDFImage.buildImage({
xref: this.xref,
@ -803,11 +829,11 @@ class PartialEvaluator {
imgData.dataLen = imgData.bitmap
? imgData.width * imgData.height * 4
: imgData.data.length;
imgData.ref = imageRef;
if (cacheKey && imageRef && cacheGlobally) {
if (cacheGlobally) {
this.globalImageCache.addByteSize(imageRef, imgData.dataLen);
}
return this._sendImgData(objId, imgData, cacheGlobally);
})
.catch(reason => {
@ -816,8 +842,6 @@ class PartialEvaluator {
return this._sendImgData(objId, /* imgData = */ null, cacheGlobally);
});
operatorList.addImageOps(OPS.paintImageXObject, args, optionalContent);
if (cacheKey) {
const cacheData = {
fn: OPS.paintImageXObject,
@ -830,8 +854,6 @@ class PartialEvaluator {
this._regionalImageCache.set(/* name = */ null, imageRef, cacheData);
if (cacheGlobally) {
assert(!isInline, "Cannot cache an inline image globally.");
this.globalImageCache.setData(imageRef, {
objId,
fn: OPS.paintImageXObject,

32
src/display/api.js
View File

@ -2704,11 +2704,11 @@ class WorkerTransport {
messageHandler.on("commonobj", ([id, type, exportedData]) => {
if (this.destroyed) {
return; // Ignore any pending requests if the worker was terminated.
return null; // Ignore any pending requests if the worker was terminated.
}
if (this.commonObjs.has(id)) {
return;
return null;
}
switch (type) {
@ -2750,6 +2750,23 @@ class WorkerTransport {
this.commonObjs.resolve(id, font);
});
break;
case "CopyLocalImage":
const { imageRef } = exportedData;
assert(imageRef, "The imageRef must be defined.");
for (const pageProxy of this.#pageCache.values()) {
for (const [, data] of pageProxy.objs) {
if (data.ref !== imageRef) {
continue;
}
if (!data.dataLen) {
return null;
}
this.commonObjs.resolve(id, structuredClone(data));
return data.dataLen;
}
}
break;
case "FontPath":
case "Image":
case "Pattern":
@ -2758,6 +2775,8 @@ class WorkerTransport {
default:
throw new Error(`Got unknown common object type ${type}`);
}
return null;
});
messageHandler.on("obj", ([id, pageIndex, type, imageData]) => {
@ -3166,6 +3185,15 @@ class RenderTask {
* @type {function}
*/
this.onContinue = null;
if (typeof PDFJSDev === "undefined" || PDFJSDev.test("TESTING")) {
// For testing purposes.
Object.defineProperty(this, "getOperatorList", {
value: () => {
return this.#internalRenderTask.operatorList;
},
});
}
}
/**

38
test/unit/api_spec.js
View File

@ -3811,14 +3811,36 @@ Caron Broadcasting, Inc., an Ohio corporation (“Lessee”).`)
const loadingTask = getDocument(
buildGetDocumentParams("issue11878.pdf", {
isOffscreenCanvasSupported: false,
pdfBug: true,
})
);
const pdfDoc = await loadingTask.promise;
let firstImgData = null;
let checkedCopyLocalImage = false,
firstImgData = null,
firstStatsOverall = null;
for (let i = 1; i <= pdfDoc.numPages; i++) {
const pdfPage = await pdfDoc.getPage(i);
const opList = await pdfPage.getOperatorList();
const viewport = pdfPage.getViewport({ scale: 1 });
const canvasAndCtx = CanvasFactory.create(
viewport.width,
viewport.height
);
const renderTask = pdfPage.render({
canvasContext: canvasAndCtx.context,
viewport,
});
await renderTask.promise;
const opList = renderTask.getOperatorList();
// The canvas is no longer necessary, since we only care about
// the image-data below.
CanvasFactory.destroy(canvasAndCtx);
const [statsOverall] = pdfPage.stats.times
.filter(time => time.name === "Overall")
.map(time => time.end - time.start);
const { commonObjs, objs } = pdfPage;
const imgIndex = opList.fnArray.indexOf(OPS.paintImageXObject);
@ -3843,6 +3865,7 @@ Caron Broadcasting, Inc., an Ohio corporation (“Lessee”).`)
// Ensure that the actual image data is identical for all pages.
if (i === 1) {
firstImgData = objs.get(objId);
firstStatsOverall = statsOverall;
expect(firstImgData.width).toEqual(EXPECTED_WIDTH);
expect(firstImgData.height).toEqual(EXPECTED_HEIGHT);
@ -3854,6 +3877,8 @@ Caron Broadcasting, Inc., an Ohio corporation (“Lessee”).`)
const objsPool = i >= NUM_PAGES_THRESHOLD ? commonObjs : objs;
const currentImgData = objsPool.get(objId);
expect(currentImgData).not.toBe(firstImgData);
expect(currentImgData.width).toEqual(firstImgData.width);
expect(currentImgData.height).toEqual(firstImgData.height);
@ -3866,11 +3891,20 @@ Caron Broadcasting, Inc., an Ohio corporation (“Lessee”).`)
return value === firstImgData.data[index];
})
).toEqual(true);
if (i === NUM_PAGES_THRESHOLD) {
checkedCopyLocalImage = true;
// Ensure that the image was copied in the main-thread, rather
// than being re-parsed in the worker-thread (which is slower).
expect(statsOverall).toBeLessThan(firstStatsOverall / 5);
}
}
}
expect(checkedCopyLocalImage).toBeTruthy();
await loadingTask.destroy();
firstImgData = null;
firstStatsOverall = null;
});
it("render for printing, with `printAnnotationStorage` set", async function () {