Hi Friends,
I realize that we're expecting the new renderer, planned for release with version 0.49 (sometime next year) which will hopefully resolve many of these issues. But it seems like I've been answering these questions a lot lately. So I wanted to make a short tutorial, to which I and others can link, rather than type the same explanation every time. At least until the new renderer is available.....although, I suspect it won't be long before folks begin to challenge even the shiny new renderer, and then these tips might still be useful. (There are some older topics on this issue, but they seem a little outdated, as some things have changed in this area, over the last few new releases.)

If Inkscape starts to work very slowly, whether suddenly or gradually, or sometimes might even crash, there are probably some things you can do to improve the situation. If you're in a hurry at this moment, jump down to "***Ok, .....". Otherwise, I think it will be helpful to mention some things that can contribute to performance issues, first. In some cases, you can plan how to create your graphics, and perhaps not run into these problems in the first place, or at least minimize it from the start. Pre-planning can be especially important for photo-realistic work, in my experience

These things can increase the file size, and potentially create performance issues:

• embedded images
• certain Filters or combinations of filters or number of filters -- note that Blur is a very simple filter, but using a lot of it can still cause problems
• certain Extensions or combinations of extensions or number of uses of extensions
• large quantity of Nodes
• a lot of gradients
• extreme zooming in combination with the above
• various combinations of the above

In general, the more RAM you have on the computer where you're using Inkscape, the less you'll have this kind of problem. These days, 4 gb RAM seems to be a minimum requirement. You can certainly use Inkscape with less RAM, but these perfomance problems will proliferate, sometimes even in small files. [Off Topic: If anyone knows where minimum system requirements for running Inkscape can be found, please let me know ]

If you have a desktop computer, you might be able to buy and add more RAM yourself! I've actually done it myself, and it's not hard or complicated, and doesn't take a long time. I actually found more info by googling, than my computer's manufacturer provided. The little RAM gadgets (whatever they're called -- cards?) are.....well-ll-ll....I'd say moderately expensive, but not outrageous. To my understanding, it's not possible for ordinary users to add RAM to a laptop. I learned that too late. If I'd known, I would've bought my laptop with more RAM.

***Ok, now for the tips to avoid these problems:

• Divide your file into layers, and maybe even sublayers. Then you can hide all the layers that you don't need at the moment. Since Inkscape doesn't need to display hidden layers, it frees up resources for whatever you're working on.
• If you're using an embedded image as a reference, either delete it from the file as soon as you no longer need it, or move it to another layer where you can hide it.
• Use View menu > Display Mode > No Filters. This has a similar effect that hiding layers has -- it frees up more RAM for whatever you're working on.
• If you have a huge number of nodes, you might not need them, depending on the circumstances. If not, you could try Path menu > Simplify, which potentially could drastically reduce the number of nodes. In certain situations though, it can distort the path, so just be ready to Undo, if the result is not acceptable.
• Use View menu > Display Mode > Outline, to prevent Inkscape from displaying gradients, which again, frees up some RAM.
• Avoid extreme zooming, and zoom only as much as you need. If I have to zoom, and I know it will take a long time, I've found that I can scroll over to an empty area of canvas, zoom to whatever level I need, then scroll back into the area where I need to work. It's much faster than waiting, waiting, waiting, for Inkscape to reach a high zoom in a large file.

Well that's about all I can think of at the moment. I've got that nagging feeling that I forgot something, so if I've left out anything, please feel free to reply with more tips or info

1) In File > Inkscape Preferences, in the Rendering section, you can adjust the trade-off between quality and speed for Gaussian blur and other filters.

2) Just because you bought a shiny new widescreen monitor it doesn't mean you have to run Inkscape full screen. I have my Inkscape window at full height but about 2/3 of the width of the screen, positioned in the centre. That way when I zoom in Inkscape has less to draw, which is faster (especially with filters involved).

3) If you've got a complex part of your drawing, possibly filled with filters or blurs, which is slowing Inkscape's rendering then you can move it to a different layer and hide the layer, as Brynn suggested. Sometimes, however, you still need to see those parts for reference or context. In this case you can select the problem objects then use Edit > Make a Bitmap Copy to create a "snapshot" of those objects as a bitmap. Move the bitmap onto a visible layer and hide the one with the problem objects on it. The bitmap will render much faster than the original objects and is usually good enough to provide a little context. Don't forget to delete the bitmap and unhide the objects' layer when you're done though!

Ah-ha! One more thing I can add.

If your computer uses more than 1 core (I think called processors?) you can change a setting in Inkscape Preferences, to have them better utilized. Depending on your version, you may either find it under Filter, or Rendering. Change the Number of Thread to however many cores/processors you have. If you're not sure, change it to say 12, and after you restart Inkscape, it will be set to however many you actually have. (It is possible to have more than 12, but I don't think it's very common to have more than that.)

My current understanding is that this only helps with display of filters (which includes a simple blur). But I could be wrong about that. Will update as soon as I learn

Edit
Ok, here's the poop. Pre 0.49 the multi-threading helps only with displaying gaussian blur filters. 0.49 and after, it helps with any kind of filters

curious captain, you speak of 0.49 but the latest stable release I could find is 0.48.4. has 0.49 been released? thanks.

Thanks for posting these tips. I've been working with the 64x64 canvas exclusively and anytime I used a filter, it was tanking inkscape for minutes on end and then it became unusable with the filter applied. I'm running on a 5i+SDD+32g of ram. I thought the build was buggy or something. The suggestion to zoom out before messing with filters works great though. I think the thread thing might have helped a little bit as well.

Anyway, thanks again.

Update

Note that since I wrote this, it was decided to give the next major version the number 0.91 (instead of 0.49). I don't really know why. But we're getting very close to the release of 0.91 now! If you can't wait, it's already available in developmental 0.91pre2 (https://inkscape.org/en/download/).

This is material for a sticky no? "Performance issues in Inkscape" or something? And then just the tips, without further ado? The less clutter, the better. Like "Here are some tips to try out when you have performance issues in Inkscape (slow rendering, ...): " and then a bullet list.
And/or maybe even a tutorial/FAQ on inkscape.org.
No?

No one here has access to that part of the forum. Only the owner, who apparently doesn't keep up with forum activity.

But maybe I'll write up a new tutorial, where it will be linked from the FAQ on my Inkscape website (links in my signature). I guess I was hoping the new renderer in 0.91 would reduce a lot of message that are posted about performance issues. But yours was the 2nd time since 0.91 came out, that I referred someone to this topic. I guess it could be helpful anyway though. So I'll start working on that.

I know that will not help here. But then again, no one here has access.

And I certainly cannot WAIT until the Inkscape website will show images that are uploaded into the gallery with Tutorials category, on the Tutorials page. I'm planning to use that feature a lot, when it's ready!

And by the way, if anyone is interested, the Inkscape website needs a long term content manager/webmaster, in the worst way. While development of the website is continuing, new content is more or less on hold, until someone with the right experience volunteers. (Or maybe some other jobs on that list will catch someone's attention??)