On Thu, Jun 10, 2021 at 10:56 AM Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> wrote: > > On Thu, 2021-06-10 at 10:31 -0400, Olga Kornievskaia wrote: > > On Thu, Jun 10, 2021 at 10:13 AM Trond Myklebust > > <trondmy@xxxxxxxxxxxxxxx> wrote: > > > > > > On Thu, 2021-06-10 at 13:56 +0000, Chuck Lever III wrote: > > > > > > > > > > > > > On Jun 10, 2021, at 9:34 AM, Trond Myklebust < > > > > > trondmy@xxxxxxxxxxxxxxx> wrote: > > > > > > > > > > On Thu, 2021-06-10 at 13:30 +0000, Chuck Lever III wrote: > > > > > > > > > > > > > > > > > > > On Jun 9, 2021, at 5:53 PM, Olga Kornievskaia < > > > > > > > olga.kornievskaia@xxxxxxxxx> wrote: > > > > > > > > > > > > > > From: Olga Kornievskaia <kolga@xxxxxxxxxx> > > > > > > > > > > > > > > This option will control up to how many xprts can the > > > > > > > client > > > > > > > establish to the server. This patch parses the value and > > > > > > > sets > > > > > > > up structures that keep track of max_connect. > > > > > > > > > > > > > > Signed-off-by: Olga Kornievskaia <kolga@xxxxxxxxxx> > > > > > > > --- > > > > > > > fs/nfs/client.c | 1 + > > > > > > > fs/nfs/fs_context.c | 8 ++++++++ > > > > > > > fs/nfs/internal.h | 2 ++ > > > > > > > fs/nfs/nfs4client.c | 12 ++++++++++-- > > > > > > > fs/nfs/super.c | 2 ++ > > > > > > > include/linux/nfs_fs_sb.h | 1 + > > > > > > > 6 files changed, 24 insertions(+), 2 deletions(-) > > > > > > > > > > > > > > diff --git a/fs/nfs/client.c b/fs/nfs/client.c > > > > > > > index 330f65727c45..486dec59972b 100644 > > > > > > > --- a/fs/nfs/client.c > > > > > > > +++ b/fs/nfs/client.c > > > > > > > @@ -179,6 +179,7 @@ struct nfs_client > > > > > > > *nfs_alloc_client(const > > > > > > > struct nfs_client_initdata *cl_init) > > > > > > > > > > > > > > clp->cl_proto = cl_init->proto; > > > > > > > clp->cl_nconnect = cl_init->nconnect; > > > > > > > + clp->cl_max_connect = cl_init->max_connect ? > > > > > > > cl_init- > > > > > > > > max_connect : 1; > > > > > > > > > > > > So, 1 is the default setting, meaning the "add another > > > > > > transport" > > > > > > facility is disabled by default. Would it be less surprising > > > > > > for > > > > > > an admin to allow some extra connections by default? > > > > > > > > > > > > > > > > > > > clp->cl_net = get_net(cl_init->net); > > > > > > > > > > > > > > clp->cl_principal = "*"; > > > > > > > diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c > > > > > > > index d95c9a39bc70..cfbff7098f8e 100644 > > > > > > > --- a/fs/nfs/fs_context.c > > > > > > > +++ b/fs/nfs/fs_context.c > > > > > > > @@ -29,6 +29,7 @@ > > > > > > > #endif > > > > > > > > > > > > > > #define NFS_MAX_CONNECTIONS 16 > > > > > > > +#define NFS_MAX_TRANSPORTS 128 > > > > > > > > > > > > This maximum seems excessive... again, there are diminishing > > > > > > returns to adding more connections to the same server. what's > > > > > > wrong with re-using NFS_MAX_CONNECTIONS for the maximum? > > > > > > > > > > > > As always, I'm a little queasy about adding yet another mount > > > > > > option. Are there real use cases where a whole-client setting > > > > > > (like a sysfs attribute) would be inadequate? Is there a way > > > > > > the client could figure out a reasonable maximum without a > > > > > > human intervention, say, by counting the number of NICs on > > > > > > the system? > > > > > > > > > > Oh, hell no! We're not tying anything to the number of NICs... > > > > > > > > That's a bit of an over-reaction. :-) A little more explanation > > > > would be welcome. I mean, don't you expect someone to ask "How > > > > do I pick a good value?" and someone might reasonably answer > > > > "Well, start with the number of NICs on your client times 3" or > > > > something like that. > > > > > > > > IMO we're about to add another admin setting without > > > > understanding > > > > how it will be used, how to select a good maximum value, or even > > > > whether this maximum needs to be adjustable. In a previous e-mail > > > > Olga has already demonstrated that it will be difficult to > > > > explain > > > > how to use this setting with nconnect=. > > > > > > > > Thus I would favor a (moderate) soldered-in maximum to start > > > > with, > > > > and then as real world use cases arise, consider adding a tuning > > > > mechanism based on actual requirements. > > > > > > It's not an overreaction. It's insane to think that counting NICs > > > gives > > > you any notion whatsoever about the network topology and > > > connectivity > > > between the client and server. It doesn't even tell you how many of > > > those NICs might potentially be available to your application. > > > > > > We're not doing any automation based on that kind of layering > > > violation. > > > > I'm not suggesting to programmatically determine the number of NIC to > > determine the value of max_connect. > > > > > No, but that's what Chuck appeared to be suggesting in order to avoid > the need for the mount option. > > To me, the main reason for the mount option is to allow the user to > limit the number of new IP addresses being added so that if the DNS > server is configured to hand out lots of different addresses for the > same servername, the user can basically say 'no, I just want to use the > one IP address that I'm already connected to' (i.e. max_connect=1). I > can imagine that some clustered setups might need that ability in order > to work efficiently. > > I'm fine with the idea of nconnect setting the number of connections > per IP address, but that would need some plumbing in > rpc_clnt_test_and_add_xprt() to allow us to add up to 'nconnect' copies > of a given transport. > Presumably rpc_xprt_switch_has_addr() would need to return a count of > the number of copies of the transport that are already present so that > we can decide whether or not we should add a new one. I think the last paragraph is what I'm asking for. But I would like to again confirm if you still mean "max_connect" to be the total number of connections since you say we could/will allow for nconnect number of connections per IP address. Would max_connect need to be a multiple of nconnect (max_connect = X *nconnect)? Actually when I said supporting (or rather allowing for) nconnect * max_connect transport, is that correct? Given how the code works now this is going to be nconnect + max_connect (only if 1st mount had nconnect option). We can't "add" nconnect connections to the new mounts (but with my patch we can add a single trunk connection). By that I mean: say the first was "mount IP1:/vol1 /mnt1" (1 connection to IP2). Now the client is doing "mount IP2:/vol2 /mnt2". IP1 and IP2 are trunkable addresses of the same server so we add a trunk. We currently don't allow for doing "mount -o nconnec=2 IP2:vol2 /mnt2" and then also add "nconnect" connections to IP2 along with a trunk. In the 2nd example, we'd have 1 connections to IP1, then 2 connections to IP2. Can we allow for that (with needed code change)? If not, then we really need to commit to only support nconnect (16) connections + some number of trunkable connections. > > -- > Trond Myklebust > Linux NFS client maintainer, Hammerspace > trond.myklebust@xxxxxxxxxxxxxxx > >
