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; > > > } > > > >
