Why does speech recognition take up 1 GB or RAM suddenly? And Gmail in Safari 738 MB

Here's a few things I would try:

1. Do basic system maintenance (repair permissions, clean caches, run daily-weekly-monthly maintenance scripts). I like ONYX (http://bit.ly/eCzYfj) for doing this, but there are plenty of other options that do the same thing.

2. Make sure you have at least 20% free disk space. If not, try clean up and free some space.

3. If things are still slow, try creating a new user account and logging in with that. If that account runs much better you still have some cleanup to do.

4. Check your login items (in system preferences, User & Groups). If there are login items you don't recognize/need try disabling them.

I would also look into investing in at least a 2MB memory upgrade. Not too expensive and it looks like you could use it.

Good luck...

Mavericks' new memory management tool was designed to do exactly that, use AS MUCH RAM as possible. See, "free ram" doesn't actually do anything until it's used. It's just there idle, waiting to be allocated. Mavericks uses physical memory much more in order to speed up actions. For example, closed applications and file will be cached until memory is needed, at which point they can be overwritten.

For example, my 24GB machine currently has around 14GB of file caches (after around 5 weeks of uptime). In total, 18 GB of my 24 is used. This demonstrates Mavericks attempt to cache everything possible. If not for file caches, I'd only be using 4GB of my 24GB of RAM, basically rendering 20GB (~83%) of my system memory (costing well over $300) as completely unused.

I don't think your performance issues are a result of the new memory management. If anything, there should be decreased disk access, faster load times, etc. You can try troubleshooting by running sudo purge in terminal to force the deletion of file caches and inactive pages. (Note: Free RAM ≠ faster performance)