This original code in nfsd4_get_drc_mem() would hand out 30 slots (approximately NFSD_MAX_MEM_PER_SESSION bytes at slightly over 2K per slot) to each requesting client until it ran out of space, then it would possibly give one last client a reduced allocation, then fail the allocation. Since commit de766e570413 ("nfsd: give out fewer session slots as limit approaches") the last 90 slots to be given to about 12 clients with quickly reducing slot counts (better than just 3 clients). This still seems unnecessarily hasty. A subsequent patch allows over-allocation so every client gets at least one slot, but that might be a bit restrictive. The requested number of nfsd threads is the best guide we have to the expected number of clients, so use that - if it is at least 8. 256 threads on a 256Meg machine - which is a lot for a tiny machine - would result in nfsd_drc_max_mem being 2Meg, so 8K (3 slots) would be available for the first client, and over 200 clients would get more than 1 slot. So I don't think this change will be too debilitating on poorly configured machines, though it does mean that a sensible configuration is a little more important. Signed-off-by: NeilBrown --- fs/nfsd/nfs4state.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 084a30d77359..c49af2ba3924 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -1563,11 +1563,12 @@ static inline u32 slot_bytes(struct nfsd4_channel_attrs *ca) * re-negotiate active sessions and reduce their slot usage to make * room for new connections. For now we just fail the create session. */ -static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca) +static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca, struct nfsd_net *nn) { u32 slotsize = slot_bytes(ca); u32 num = ca->maxreqs; unsigned long avail, total_avail; + unsigned int scale_factor; spin_lock(&nfsd_drc_lock); if (nfsd_drc_max_mem > nfsd_drc_mem_used) @@ -1581,12 +1582,18 @@ static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca) total_avail = 0; 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 fraction of the remaining memory, * unless it's the only way to give this client a slot. + * The chosen fraction is either 1/8 or 1/number of threads, + * whichever is smaller. This ensures there are adequate + * slots to support multiple clients per thread. * Give the client one slot even that would require * over-allocation, it is better than failure. */ - avail = clamp_t(unsigned long, avail, slotsize, total_avail/3); + scale_factor = max_t(unsigned int, 8, nn->nfsd_serv->sv_nrthreads); + + avail = clamp_t(unsigned long, avail, slotsize, + total_avail/scale_factor); num = min_t(int, num, avail / slotsize); num = max_t(int, num, 1); nfsd_drc_mem_used += num * slotsize; @@ -3183,7 +3190,7 @@ static __be32 check_forechannel_attrs(struct nfsd4_channel_attrs *ca, struct nfs * Note that we always allow at least one slot, because our * accounting is soft and provides no guarantees either way. */ - ca->maxreqs = nfsd4_get_drc_mem(ca); + ca->maxreqs = nfsd4_get_drc_mem(ca, nn); return nfs_ok; } -- 2.23.0