[9fans] Adding lookup() to 9p?

[9fans] Adding lookup() to 9p?

[Go Phone]

Hello,

Key-value lookups are expensive over 9p. We need a walk(), open(),
read() and close(). I am wondering if adding a lookup() function to
struct Dev adds much value?

Thanks
Joe

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[9fans] Re: Adding lookup() to 9p?

[wb.kloke]

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Though I see your point, you will need to show a really important improvement to justify any change in 9p protocol.

Best thing you can do: Implement it on your own source, and show the benefits.
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Re: [9fans] Adding lookup() to 9p?

[ori]

Quoth Go Phone <gophone2015@gmail.com>:
> Hello,
> 
> Key-value lookups are expensive over 9p. We need a walk(), open(),
> read() and close(). I am wondering if adding a lookup() function to
> struct Dev adds much value?
> 
> Thanks
> Joe
> 

note that you need a separate Twalk message no matter what,
so you can determine if you're crossing a mountpoint. Imagine:

        # starting fronm a fresh ns, put a file
        # on the real file system there
        % mkdir /usr/ori/kv
        % touch /usr/ori/kv/value
        # then mount in the kv store
        % bind /dev/null /usr/ori/kv/store/value
        # then do a lookup
        % lookup /usr/ori/kv/store/value

Because 'lookup' would be a single message,
you'd return the empty file from the root
file system, and not cross the mountpoint
into the kv store.


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Re: [9fans] Adding lookup() to 9p?

[Steve Simon]

can you give some examples of where this new api would be used?

nemo added a readfile and (i think) writefile message in his fork. that was aimed at transferring large sequential files from a fileserver.

there was also many discussions of doing parallel or chained reads to improve 9p performance 


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