linux-kernel - Re: [git pull] vfs part 2

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Message-ID: <20150702145907.08e6eb9c@tlielax.poochiereds.net>
Date:	Thu, 2 Jul 2015 14:59:07 -0400
From:	Jeff Layton <jlayton@...chiereds.net>
To:	Dominique Martinet <dominique.martinet@....fr>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Andrey Ryabinin <a.ryabinin@...sung.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [git pull] vfs part 2

On Thu, 2 Jul 2015 19:56:29 +0200
Dominique Martinet <dominique.martinet@....fr> wrote:

> Jeff Layton wrote on Thu, Jul 02, 2015:
> > So p9_idpool_create should take an argument for the "end" value, and
> > then store that in a new field in p9_idpool. Then they can pass that in
> > as the "end" parm in idr_alloc. Or, they could give up using the same
> > function there and use a different one for tags and FIDs.
> > 
> > In any case...allowing this thing to allocate tag values that can
> > collide seems fundamentally wrong. Using idr_alloc_cyclic might also
> > not hurt either, particularly given that these tag values are supposed
> > to function something like an XID and you probably don't want to be
> > reusing them too quickly.
> 
> Using cache=none here so behavious is likely different with cache, but
> basically you can't get more than one tag per user thread accessing the
> 9P mount...
> And in RDMA there's a credit so I can't get past whatever sq option was
> given (defaults to 32) -- tbh even with other transports I doubt it's
> going to get much higher.
> 
> Still definitely needs fixing, but I think the issue is somewhere
> else... If Andrey could share the workload he uses I can try with other
> servers, would be nice if we can rule a qemu bug out completely :)
> 

Fair enough...

If you're in there and decide to fix this up, then consider moving this
over to IDA instead of IDR. The pointers stored are not terribly
interesting (always the same as the p9_idpool), so by doing that you'll
save quite a bit of memory as well.

-- 
Jeff Layton <jlayton@...chiereds.net>
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