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Date: Tue, 14 Jul 2015 09:29:14 -0600 From: Jens Axboe <axboe@...com> To: Mike Snitzer <snitzer@...hat.com> CC: <linux-kernel@...r.kernel.org>, <hch@....de> Subject: Re: [PATCH 2/2] block: make /sys/block/<dev>/queue/discard_max_bytes writeable On 07/14/2015 09:23 AM, Mike Snitzer wrote: > On Tue, Jul 14 2015 at 11:02am -0400, > Jens Axboe <axboe@...com> wrote: > >> Lots of devices support huge discard sizes these days. Depending >> on how the device handles them internally, huge discards can >> introduce massive latencies (hundreds of msec) on the device side. >> >> We have a sysfs file, discard_max_bytes, that advertises the max >> hardware supported discard size. Make this writeable, and split >> the settings into a soft and hard limit. This can be set from >> 'discard_granularity' and up to the hardware limit. > > Looks pretty good, but we'll lose the original discard_max_bytes once it > is changed. That information loss will prevent users from knowing what > adjustments are possible over time. > > This may be OK, but figured i'd raise it. That's true, I should have mentioned that. But if you write a higher value than the device supports, then it will be truncated to the max value that the device supports. So it's not really lost, and it was the best alternative I could think of. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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