On Mon, Aug 10, 2015 at 4:08 AM, Christoph Hellwig wrote:
> On Sun, Aug 09, 2015 at 10:50:41PM -0400, Ming Lei wrote:
>> Christoph, could you share your idea again about this approch?
>>
>> If you still don't think it is good to switch between buffered I/O
>> and direct I/O, I will not do that in
On Sun, Aug 09, 2015 at 10:50:41PM -0400, Ming Lei wrote:
> Christoph, could you share your idea again about this approch?
>
> If you still don't think it is good to switch between buffered I/O
> and direct I/O, I will not do that in next post.
If we epxose a 512 byte block size to the loop devic
On Sun, Aug 9, 2015 at 7:41 PM, Dave Chinner wrote:
> On Sun, Aug 09, 2015 at 10:27:14AM -0400, Ming Lei wrote:
>> On Sun, Aug 9, 2015 at 9:44 AM, Christoph Hellwig wrote:
>> > On Sun, Aug 09, 2015 at 09:04:32AM -0400, Ming Lei wrote:
>> >> Now the logical block size of loop is 512byte, but the s
On Sun, Aug 09, 2015 at 10:27:14AM -0400, Ming Lei wrote:
> On Sun, Aug 9, 2015 at 9:44 AM, Christoph Hellwig wrote:
> > On Sun, Aug 09, 2015 at 09:04:32AM -0400, Ming Lei wrote:
> >> Now the logical block size of loop is 512byte, but the sector size of
> >> backing device may be 4K, so we can't d
On Sun, Aug 9, 2015 at 9:44 AM, Christoph Hellwig wrote:
> On Sun, Aug 09, 2015 at 09:04:32AM -0400, Ming Lei wrote:
>> Now the logical block size of loop is 512byte, but the sector size of
>> backing device may be 4K, so we can't do 512 byte algined direct
>> I/O to the filesystem in this situati
On Sun, Aug 09, 2015 at 09:04:32AM -0400, Ming Lei wrote:
> Now the logical block size of loop is 512byte, but the sector size of
> backing device may be 4K, so we can't do 512 byte algined direct
> I/O to the filesystem in this situation.
>
> With runtime switch to buffered I/O we can fix this pr
On Sun, Aug 9, 2015 at 2:44 AM, Christoph Hellwig wrote:
> On Fri, Aug 07, 2015 at 04:25:52AM -0400, Ming Lei wrote:
>> On Fri, Aug 7, 2015 at 3:43 AM, Christoph Hellwig wrote:
>> > I really disagree with the per-cmd use_dio tracking.
>>
>> Could you explain it in a bit?
>>
>> >
>> > If we know a
On Fri, Aug 07, 2015 at 04:25:52AM -0400, Ming Lei wrote:
> On Fri, Aug 7, 2015 at 3:43 AM, Christoph Hellwig wrote:
> > I really disagree with the per-cmd use_dio tracking.
>
> Could you explain it in a bit?
>
> >
> > If we know at setup time that the loop device sector size is smaller
> > than
On Fri, Aug 7, 2015 at 3:43 AM, Christoph Hellwig wrote:
> I really disagree with the per-cmd use_dio tracking.
Could you explain it in a bit?
>
> If we know at setup time that the loop device sector size is smaller
> than the sector size of the underlying device we should never allow
> dio, and
I really disagree with the per-cmd use_dio tracking.
If we know at setup time that the loop device sector size is smaller
than the sector size of the underlying device we should never allow
dio, and othewise it should always work for data.
The ->transfer check also is one to be done at setup time
There are about 3 advantages to use direct I/O and AIO on
read/write loop's backing file:
1) double cache can be avoided, then memory usage gets
decreased a lot
2) not like user space direct I/O, there isn't cost of
pinning pages
3) avoid context switch for obtaining good throughput
- in buffere
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