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 <neilb@xxxxxxx>
---
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
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