Control: tags -1 + pending Hi Sergio,
On Mon, May 07, 2018 at 09:40:08PM +0200, Sergio Gelato wrote: > Source: linux > Version: 4.9.88-1 > Severity: wishlist > Tags: patch > > I've run into this capacity limitation in stretch, which is addressed > upstream in Linux 4.15 by the following commit: > > commit 44d8660d3bb0a1c8363ebcb906af2343ea8e15f6 > Author: J. Bruce Fields <bfie...@redhat.com> > Date: Tue Sep 19 20:51:31 2017 -0400 > > nfsd: increase DRC cache limit > > which trivially applies to Linux 4.9 (I haven't checked 3.16) and provides > significant relief in my use case. It would save me (and perhaps others) > work if this change could be included in Debian's 4.9 kernel packages; > otherwise I'll have to keep maintaining my own fork. (4.15 has other > issues so I don't want to use it in production yet.) > > For the benefit of others who may be running into the same problem, here > is a more detailed description. > > Symptom: an NFS server accepts only a limited number of concurrent v4.1+ > mounts. Once that limit is reached, new clients get NFS4ERR_DELAY (10008) > replies to CREATE_SESSION. (This can be seen in the server's dmesg after > rpcdebug -m nfsd -s proc.) Increasing the number of nfsd threads has no > impact on the number of mounts allowed. A server with 512MB of RAM > only accepts 7 or 8 concurrent NFSv4.1+ mounts. From the perspective of > an affected client, mount.nfs appears to hang (triggering a kernel backtrace > after 120 seconds); in reality, though, it just keeps reissuing CREATE_SESSION > calls until one of them succeeds. > > Pre-v4.1 clients are unaffected by this since sessions are new to NFS v4.1. > > The proposed patch just increases the limit by an order of magnitude, at > the cost of using more kernel memory. As noted in comments in the source > code, it would be nice to make this tuneable by the server administrator. Alright, I have added 44d8660d3bb0a1c8363ebcb906af2343ea8e15f6 in the stretch branch, so it will be included in the next point release update for src:linux packages. Regards, Salvatore