Darren Reed wrote:
> James Mansion wrote:
>> Is it feasible to enable swap to any remote file or remote block 
>> device with (Open)Solaris- without
>> risking a deadlock?
>
> I don't know about iSCSI, but I do know that Solaris *did* swap over NFS.
>
> Why don't you set up a test system and give it a try?
>
> Darren
>

Because that would be a pointless waste of time?

Seriously, the sort of low-memory race that can trigger such a deadlock 
isn't necessarily
straightforward to trigger in lab conditions, and its the sort of thing 
that needs to be
designed out.  You need to make sure that in low memory conditions the 
IP stack has
somewhere to assemble responses to iSCSI requests related to swap such 
that it can do
so without any possibility of causing allocation or anything else that 
can cause a page-out.
This is something that can only be there by careful design.

Its not somethng that I could infer from 'seems to work when I tried'.

I'm assuming that if Solaris did support swap over NFS then - hopefully 
- there is at least
some support for TCP stack memory reservation to support swapping and - 
hopefully - that's
also been used in the iSCSI subsystem.  But only those who know the 
implementation details
can confirm this.

So I'm asking.  Is that unreasonable?  Where else should I ask?


James

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