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Re: posix message queues and multiple receivers
On 3 December 2013 22:45, David Laight <david%l8s.co.uk@localhost> wrote:
> On Tue, Nov 26, 2013 at 01:32:44PM -0500, Mouse wrote:
>> When serving a request takes nontrivial time, and multiple requests can
>> usefully be in progress at once, it is useful - it typically improves
>> performance - to have multiple workers serving requests. NFS, as
>> mentioned above, is a fairly good example (in these respects).
> Except that NFS is a bad example, and mostly should have a single server.
> If you could arrange a NFS server for each disk spindle you might win.
> But what tends to happen is that the disk 'elevator' algorithm makes
> one of the server process wait ages for its disk access to complete,
> by which time the client has timed out and resubmitted the RPC request.
> The effect is that a slightly overloaded NFS server hits a catastrophic
> overload and transfer rates become almost zero.
> Run a single nfsd and it all works much better.
On that basis should the NetBSD default be changed from -n 4?
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