On 10-11-18 12:19 PM, James Bottomley wrote:
Not stepping into the debate: I'm happy to see punch go to the mapping data and FITRIM pick it up later. However, I think it's time to question whether we actually still want to allow online discard at all. Most of the benchmarks show it to be a net lose to almost everything (either SSD or Thinly Provisioned arrays), so it's become an "enable this to degrade performance" option with no upside.
I also suspect that online TRIM exerts significant premature wear on the SSDs. TRIM operations most likely trigger immediate copy/erase operations internal to most SSDs, often regardless of the amount of data being trimmed. Performing a 256KB erase because of a 1024-byte TRIM, over and over, is going to harm the expected lifetime of an SSD. Sure, some SSDs may do things differently internally, but I don't see it working that way in much of the current crop of SSDs. Currently, I patch my kernels to remove the automatic online TRIMs. Is there a knob somewhere for this in the later kernels? Cheers -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
