Re: [PATCH] blk: don't account discard request size

From: Jeff Moyer
Date: Wed May 13 2015 - 11:49:06 EST

Jens Axboe <axboe@xxxxxx> writes:

> On 05/13/2015 11:00 AM, Jeff Moyer wrote:
>> Jens Axboe <axboe@xxxxxx> writes:
>>> That would be better. But I'm still not sure we want to turn off
>>> accounting for discards. For the mixed write/discard cases it's
>>> definitely confusing. The better option would be to account it as a
>>> discard and not a write. Preferably in a way that would not break
>>> existing tools, but so that they could get updated to support it.
>> Are you suggesting adding a few fields to the end of diskstats or adding
>> a new proc file altogether? (or something else?)
> I didn't suggest any specific solution. Obviously it'd be nice if we
> could just extend diskstats, but that might break userland. Worth
> checking up on.

OK, I didn't know if you had any other tricks up your sleeve. We've had
luck adding fields to the end of some files in the past (I'd really have
to dig to remember what files), but I'm fairly certain this would break
*something*. It's definitely safer (albeit uglier) to just add a file.

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