Re: [PATCH 4/6] nfsd: allocate new session-based DRC slots on demand.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, 2024-11-19 at 11:41 +1100, NeilBrown wrote:
> If a client ever uses the highest available slot for a given session,
> attempt to allocate another slot so there is room for the client to use
> more slots if wanted.  GFP_NOWAIT is used so if there is not plenty of
> free memory, failure is expected - which is what we want.  It also
> allows the allocation while holding a spinlock.
> 
> We would expect to stablise with one more slot available than the client
> actually uses.
> 
> Now that we grow the slot table on demand we can start with a smaller
> allocation.  Define NFSD_MAX_INITIAL_SLOTS and allocate at most that
> many when session is created.
> 
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> ---
>  fs/nfsd/nfs4state.c | 32 ++++++++++++++++++++++++++------
>  fs/nfsd/state.h     |  2 ++
>  2 files changed, 28 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 31ff9f92a895..fb522165b376 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -1956,7 +1956,7 @@ static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *fattrs,
>  	if (!slot || xa_is_err(xa_store(&new->se_slots, 0, slot, GFP_KERNEL)))
>  		goto out_free;
>  
> -	for (i = 1; i < numslots; i++) {
> +	for (i = 1; i < numslots && i < NFSD_MAX_INITIAL_SLOTS; i++) {

nit: maybe just clamp numslots at NFSD_MAX_INITIAL_SLOTS?

>  		slot = kzalloc(slotsize, GFP_KERNEL | __GFP_NORETRY);
>  		if (!slot)
>  			break;
> @@ -4248,11 +4248,6 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	slot = xa_load(&session->se_slots, seq->slotid);
>  	dprintk("%s: slotid %d\n", __func__, seq->slotid);
>  
> -	/* We do not negotiate the number of slots yet, so set the
> -	 * maxslots to the session maxreqs which is used to encode
> -	 * sr_highest_slotid and the sr_target_slot id to maxslots */
> -	seq->maxslots = session->se_fchannel.maxreqs;
> -
>  	trace_nfsd_slot_seqid_sequence(clp, seq, slot);
>  	status = check_slot_seqid(seq->seqid, slot->sl_seqid,
>  					slot->sl_flags & NFSD4_SLOT_INUSE);
> @@ -4302,6 +4297,31 @@ nfsd4_sequence(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  	cstate->session = session;
>  	cstate->clp = clp;
>  
> +	/*
> +	 * If the client ever uses the highest available slot,
> +	 * gently try to allocate another one.
> +	 */
> +	if (seq->slotid == session->se_fchannel.maxreqs - 1 &&
> +	    session->se_fchannel.maxreqs < NFSD_MAX_SLOTS_PER_SESSION) {
> +		int s = session->se_fchannel.maxreqs;
> +
> +		/*
> +		 * GFP_NOWAIT is a low-priority non-blocking allocation
> +		 * which can be used under client_lock and only succeeds
> +		 * if there is plenty of memory.
> +		 * Use GFP_ATOMIC which is higher priority for xa_store()
> +		 * so we are less likely to waste the effort of the first
> +		 * allocation.
> +		 */
> +		slot = kzalloc(slot_bytes(&session->se_fchannel), GFP_NOWAIT);
> +		if (slot && !xa_is_err(xa_store(&session->se_slots, s, slot,
> +						GFP_ATOMIC)))
> +			session->se_fchannel.maxreqs += 1;
> +		else
> +			kfree(slot);
> +	}
> +	seq->maxslots = session->se_fchannel.maxreqs;
> +
>  out:
>  	switch (clp->cl_cb_state) {
>  	case NFSD4_CB_DOWN:
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index e97626916a68..a14a823670e9 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -249,6 +249,8 @@ static inline struct nfs4_delegation *delegstateid(struct nfs4_stid *s)
>   * get good throughput on high-latency servers.
>   */
>  #define NFSD_MAX_SLOTS_PER_SESSION	2048
> +/* Maximum number of slots per session to allocate for CREATE_SESSION */
> +#define NFSD_MAX_INITIAL_SLOTS		32
>  /* Maximum  session per slot cache size */
>  #define NFSD_SLOT_CACHE_SIZE		2048
>  /* Maximum number of NFSD_SLOT_CACHE_SIZE slots per session */

-- 
Jeff Layton <jlayton@xxxxxxxxxx>





[Index of Archives]     [Linux Filesystem Development]     [Linux USB Development]     [Linux Media Development]     [Video for Linux]     [Linux NILFS]     [Linux Audio Users]     [Yosemite Info]     [Linux SCSI]

  Powered by Linux