From: bfields@fieldses.org (J. Bruce Fields)
To: "J. Bruce Fields" <bfields@redhat.com>
Cc: NeilBrown <neilb@suse.de>, linux-nfs@vger.kernel.org
Subject: Re: [PATCH 2/2] nfsd: give out fewer session slots as limit approaches
Date: Thu, 19 Sep 2019 14:41:39 -0400 [thread overview]
Message-ID: <20190919184139.GG26654@fieldses.org> (raw)
In-Reply-To: <20190919171730.GB333@pick.fieldses.org>
On Thu, Sep 19, 2019 at 01:17:30PM -0400, J. Bruce Fields wrote:
> - Maybe we should just keep allowing small sessions (1 slot?)
> even past the limit. Worst case the subsequent kmalloc fails.
So to be clear, I think that's what I'd do for now instead of trying to
find a better error return.
And probably put the 1/3->1/16 change in a separate patch.
--b.
>
> --b.
>
> >
> > > Also, I'd like to suggest that the '1/3' heuristic be change to 1/16.
> > > Assuming 30 slots get handed out normally (which my testing shows -
> > > about 2k each, with an upper limit of 64k):
> > > When 90 slots left, we hand out
> > > 30 (now 60 left)
> > > 20 (now 40 left)
> > > 13 (now 27 left)
> > > 9 (now 18 left)
> > > 6 (now 12 left)
> > > 4 (now 8 left)
> > > 2 (now 6 left)
> > > 2 (now 4 left)
> > > 1
> > > 1
> > > 1
> > > 1
> > > which is a rapid decline as clients are added.
> > > With 16, we hand out 30 at a time until 480 slots are left (30Meg)
> > > then: 30 28 26 24 23 21 20 19 18 6 15 15 14 13 12 11 10 10 9 9 8 8 7 7
> > > 6 6 5 5 5 5 4 4 4 3 3 3 3 3 3 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1
> > > 1 1
> > > slots per session
> > >
> > > Am I convincing?
> > >
> > > To make it more concrete: this is what I'm thinking of. Which bits do
> > > you like?
> >
> > Except for the error return, it looks good to me.
> >
> > --b.
> >
> > >
> > > Thanks,
> > > NeilBrown
> > >
> > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > index 7857942c5ca6..5d11ceaee998 100644
> > > --- a/fs/nfsd/nfs4state.c
> > > +++ b/fs/nfsd/nfs4state.c
> > > @@ -1573,11 +1573,15 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca)
> > > total_avail = nfsd_drc_max_mem - nfsd_drc_mem_used;
> > > avail = min((unsigned long)NFSD_MAX_MEM_PER_SESSION, total_avail);
> > > /*
> > > - * Never use more than a third of the remaining memory,
> > > + * Never use more than a 1/16 of the remaining memory,
> > > * unless it's the only way to give this client a slot:
> > > */
> > > - avail = clamp_t(unsigned long, avail, slotsize, total_avail/3);
> > > + avail = clamp_t(unsigned long, avail, slotsize, total_avail/16);
> > > num = min_t(int, num, avail / slotsize);
> > > + if (nfsd_drc_mem_used + num * slotsize > nfsd_drc_max_mem)
> > > + /* Completely out of space - sorry */
> > > + num = 0;
> > > +
> > > nfsd_drc_mem_used += num * slotsize;
> > > spin_unlock(&nfsd_drc_lock);
> > >
> > > @@ -3172,7 +3176,7 @@ static __be32 check_forechannel_attrs(struct nfsd4_channel_attrs *ca, struct nfs
> > > */
> > > ca->maxreqs = nfsd4_get_drc_mem(ca);
> > > if (!ca->maxreqs)
> > > - return nfserr_jukebox;
> > > + return nfserr_resource;
> > >
> > > return nfs_ok;
> > > }
> >
> >
next prev parent reply other threads:[~2019-09-19 18:41 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-25 13:21 [PATCH 0/2] tweak knfsd session slot table sizing J. Bruce Fields
2017-09-25 13:21 ` [PATCH 1/2] nfsd: increase DRC cache limit J. Bruce Fields
2017-09-25 13:21 ` [PATCH 2/2] nfsd: give out fewer session slots as limit approaches J. Bruce Fields
2019-09-19 1:08 ` NeilBrown
2019-09-19 16:22 ` J. Bruce Fields
2019-09-19 17:17 ` J. Bruce Fields
2019-09-19 18:41 ` J. Bruce Fields [this message]
2019-09-20 6:15 ` [PATCH 1/2] nfsd: handle drc over-allocation gracefully NeilBrown
2019-09-20 6:33 ` [PATCH 1/2 - vers2] " NeilBrown
2019-09-20 6:36 ` [PATCH - 2/2] nfsd: degraded slot-count more gracefully as allocation nears exhaustion NeilBrown
2019-09-20 16:28 ` [PATCH 1/2 - vers2] nfsd: handle drc over-allocation gracefully J. Bruce Fields
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