Memory used by Photoshop: 100 %
By @Javadst
Never do that! Even if Photoshop reports a little less available (which is normal as Ged says).
First of all, Photoshop will reserve that memory within seconds, leaving nothing for other applications and processes. Setting that allocation doesn't mean Photoshop can use that memory - it means Photoshop will use that memory! That will slow down your whole system and push other things into disk paging. And once taken, the memory is not released again until the application is closed out. Instead, it gets recycled and reused as you work.
What few people know, is that even plugins like Camera Raw run outside Photoshop's address space and require their own memory in addition to what Photoshop uses.
Secondly, Photoshop doesn't really need all that memory. RAM is just a cache for the scratch disk, which is where the real heavy lifting is. There is no such thing as "enough RAM", no matter how much you have. Everything is written to scratch disk at all times. It is much more important that you have enough scratch disk space, than vast amounts of RAM. That situation was a bit different in the old days when we had slow and sluggish hard drives - but today, with ultra-fast NVMe drives, the speed difference is insignificant. The scratch disk is for all practical purposes as fast as RAM.
In short, you can safely dial that down to 80 % or so, and discover that general system responsiveness actually increases.
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