4 ms·

That doesn't necessarily mean it will be erased, it just gets put back in the list of unallocated blocks.

• Someone 16y ago
  No. Flash memory is sort-of write-once in the sense that a page starts with all bits in one state. From there, you can flip individual bits to the other state, but to flip them back, you have to flip back all of them. So, to update a single bit, you may have to read a block, erase it, update the in-memory block, then write the in-memory block. The trim command will do the 'erase block' part of this procedure before the block is actually needed for data. That speeds up a future write to that block.