Re: [PATCH v12 3/3] ipc: Do cyclic id allocation with ipcmni_extend mode

[Manfred Spraul]

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Hi Waiman,


On 3/18/19 7:46 PM, Waiman Long wrote:
> --- a/ipc/util.c
> > +++ b/ipc/util.c
> > @@ -221,9 +221,17 @@ static inline int ipc_idr_alloc(struct ipc_ids *ids, struct kern_ipc_perm *new)
> >   	 */
> >   
> >   	if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
> > +		int max_idx;
> > +
> > +		max_idx = ids->in_use*3/2;
> > +		if (max_idx > ipc_mni)
> > +			max_idx = ipc_mni;
> > +		if (max_idx < ipc_min_cycle)
> > +			max_idx = ipc_min_cycle;
>
> Why don't you use the min() and max() macros which will make it easier 
> to read?
Changed.
> >   
> >   		/* allocate the idx, with a NULL struct kern_ipc_perm */
> > -		idx = idr_alloc(&ids->ipcs_idr, NULL, 0, 0, GFP_NOWAIT);
> > +		idx = idr_alloc_cyclic(&ids->ipcs_idr, NULL, 0, max_idx,
> > +					GFP_NOWAIT);
> >   
> >   		if (idx >= 0) {
> >   			/*
> > diff --git a/ipc/util.h b/ipc/util.h
> > index 8c834ed39012..ef4e86bb2db8 100644
> > --- a/ipc/util.h
> > +++ b/ipc/util.h
> > @@ -27,12 +27,14 @@
> >    */
> >   #define IPCMNI_SHIFT		15
> >   #define IPCMNI_EXTEND_SHIFT	24
> > +#define IPCMNI_EXTEND_MIN_CYCLE	(2 << 12)
>
> How about
>
> #define IPCMNI_EXTEND_MIN_CYCLEÂÂÂ (RADIX_TREE_MAP_SIZE * 
> RADIX_TREE_MAP_SIZE)
Good idea.
Actually, "2<<12" was the initial guess.

And then I noticed that this ends up as a two level radix tree during 
testing :-)


Updated patch attached.

--

ÂÂÂ Manfred