Messages in this thread | | | Date | Tue, 27 Jan 2015 13:26:54 +0800 | Subject | Re: [PATCH v2 3/4] block: loop: introduce 'use_aio' sysfs file | From | Ming Lei <> |
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On 1/25/15, Christoph Hellwig <hch@infradead.org> wrote: > On Tue, Jan 13, 2015 at 11:44:47PM +0800, Ming Lei wrote: >> So that users can control if kernel aio is used to submit I/O. > > Why do you want a sysfs flag for this instead of a flags in ->lo_flags > at setup time? That's how all other loop-related ABI flags work.
The flag only effects performance or CPU/memory resource utilization, and I plan to change it as dio flag.
On Tue, Jan 27, 2015 at 1:57 AM, Jeff Moyer <jmoyer@redhat.com> wrote: > Ming Lei <ming.lei@canonical.com> writes: > >> So that users can control if kernel aio is used to submit I/O. > > How would a user know to choose aio or, um, /not/ aio? At the very > least, documentation is required for this. I'd rather see the option > disappear completely, though.
As the comment says in patch 4/4, using direct I/O can save memory/CPU a lot, and won't hurt throughput if I/O is from filesystem. Otherwise, user may choose to not use direct I/O for sake of throughput.
Thanks, Ming Lei
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