Re: [PATCH] zerocopy NFS updated

Hirokazu Takahashi
2002-04-16T02:21:01Z

Hi,

jakob> Won't this serialize too much ? I mean, consider the situation where we
jakob> have file-A and file-B completely in cache, while file-C needs to be
jakob> read from the physical disk.
jakob>
jakob> Three different clients (A, B and C) request file-A, file-B and file-C
jakob> respectively. The send of file-C is started first, and the sends of files
jakob> A and B (which could commence immediately and complete at near wire-speed)
jakob> will now have to wait (leaving the NIC idle) until file-C is read from
jakob> the disks.
jakob>
jakob> Even if it's not the entire file but only a single NFS request (probably 8kB),
jakob> one disk seek (7ms) is still around 85 kB, or 10 8kB NFS requests (at 100Mbit).
jakob>
jakob> Or am I misunderstanding ? Will your UDP sendpage() queue the requests ?

No problem.
On my implementation, at the beginning a knfsd grabs all pages -- a part
of file-C -- to reply to the NFS client. After that the knfsd starts to
send them. It won't block any other knfsds during disk I/Os.

Thank you,
Hirokazu Takahashi.