On 09/26/2013 01:06:41 PM, Miklos Szeredi wrote:
On Thu, Sep 26, 2013 at 5:34 PM, J. Bruce Fields
<bfields@xxxxxxxxxxxx> wrote:
> On Thu, Sep 26, 2013 at 10:58:05AM +0200, Miklos Szeredi wrote:
>> On Wed, Sep 25, 2013 at 11:07 PM, Zach Brown <zab@xxxxxxxxxx>
wrote:
>> >> A client-side copy will be slower, but I guess it does have the
>> >> advantage that the application can track progress to some
degree, and
>> >> abort it fairly quickly without leaving the file in a totally
undefined
>> >> state--and both might be useful if the copy's not a simple
constant-time
>> >> operation.
>> >
>> > I suppose, but can't the app achieve a nice middle ground by
copying the
>> > file in smaller syscalls? Avoid bulk data motion back to the
client,
>> > but still get notification every, I dunno, few hundred meg?
>>
>> Yes. And if "cp" could just be switched from a read+write syscall
>> pair to a single splice syscall using the same buffer size.
>
> Will the various magic fs-specific copy operations become
inefficient
> when the range copied is too small?
We could treat spice-copy operations just like write operations (can
be buffered, coalesced, synced).
But I'm not sure it's worth the effort; 99% of the use of this
interface will be copying whole files.
My "patch" implementation (in busybox and toybox) hits a point where it
wants to copy the rest of the file, once there are no more hunks to
apply. This is not copying a whole file. A similar thing happens with
tail when you use the +N syntax to skip start instead of end lines. I
can see sed doing a similar thing when told to operate on line ranges...
Note sure your 99% holds up here.
Rob--
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