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

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Message-ID: <20150702210009.GC25177@nautica>
Date:	Thu, 2 Jul 2015 23:00:09 +0200
From:	Dominique Martinet <dominique.martinet@....fr>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Jeff Layton <jlayton@...chiereds.net>,
	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

Al Viro wrote on Thu, Jul 02, 2015:
> On Thu, Jul 02, 2015 at 07:56:29PM +0200, Dominique Martinet wrote:
> > 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...
> 
> Yes, and...?  You can get a lot more than one user thread...  Andrey is
> using trinity(1) on client, and that's *definitely* not single-threaded -
> the whole point is stressing the damn thing.

I have run trinity quite a bit and it doesn't fork bomb as far as I can
recall, with him running it with -C100 we're not quite at 2^16 yet?

I do agree it's a problem, just don't think it's the one we're
hitting -- I'll try again on a recent kernel to see if anything changed
with rdma/tcp as well, but I'm starting to doubt I'll get any luck with
anything other than virtio; which doesn't really help since it's not the
same order of latencies.

FWIW I don't *think* trinity can issue TFlush either without user
interaction, that's a really special call. It can only happen in rpc()
or zc_rpc() if it's interrupted by ERESTARTSYS which I understand as ^C?

(I'll look into making the pools use IDA unless someone else steps up,
sure. Thanks Jeff)

-- 
Dominique
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