On (20/11/07 10:14), Lee Schermerhorn didst pronounce:
> On Tue, 2007-11-20 at 14:19 +0000, Mel Gorman wrote:
> > On (09/11/07 07:45), Christoph Lameter didst pronounce:
> > > On Fri, 9 Nov 2007, Mel Gorman wrote:
> > >
> > > > struct page * fastcall
> > > > __alloc_pages(gfp_t gfp_mask, unsigned int order,
> > > > struct zonelist *zonelist)
> > > > {
> > > > + /*
> > > > + * Use a temporary nodemask for __GFP_THISNODE allocations. If
> > > > the
> > > > + * cost of allocating on the stack or the stack usage becomes
> > > > + * noticable, allocate the nodemasks per node at boot or
> > > > compile time
> > > > + */
> > > > + if (unlikely(gfp_mask & __GFP_THISNODE)) {
> > > > + nodemask_t nodemask;
> > >
> > > Hmmm.. This places a potentially big structure on the stack. nodemask can
> > > contain up to 1024 bits which means 128 bytes. Maybe keep an array of
> > > gfp_thisnode nodemasks (node_nodemask?) and use node_nodemask[nid]?
> >
> > Went back and revisited this. Allocating them at boot-time is below but
> > essentially it is a silly and it makes sense to just have two zonelists
> > where one of them is for __GFP_THISNODE. Implementation wise, this involves
> > dropping the last patch in the set and the overall result is still a
> > reduction
> > in the number of zonelists.
>
> Hi, Mel:
>
> I'll try this out [n 24-rc2-mm1 or later].
Hold off testing for the moment. Getting all the corner cases right for
__GFP_THISNODE has turned too complicated to be considered as part of a larger
patchset. I believe it makes sense to drop the final patch and settle with
having two zonelists. One of these will be for __GFP_THISNODE allocations. We
can then tackle removing that zonelist at a later date.
This will still remove the hack, reduce the number of zonelists and
improve how MPOL_BIND policies are applied so it is still an overall
win.
I should have a revised patchset with the final one dropped posted in a
few hours.
> I have a series with yet
> another rework of policy reference counting that will be easier/cleaner
> atop your series w/o the external zonelist hung off 'BIND policies. So,
> I'm hoping your series goes into -mm "real soon now".
>
Sounds good.
> Question: Just wondering why you didn't embed the '_THISNODE nodemask
> in the pgdat_t--initialized at boot/node-hot-add time?
At the time, to save space in the pg_data_t structure but it is not
worth the complexity.
> Perhaps under
> #ifdef CONFIG_NUMA. The size is known at build time, right? And
> wouldn't that be way smaller than an additional zonelist?
>
Yes it would.
> Lee
>
> >
> > diff -rup -X /usr/src/patchset-0.6/bin//dontdiff
> > linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/gfp.h
> > linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/gfp.h
> > --- linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/gfp.h
> > 2007-11-19 19:27:15.000000000 +0000
> > +++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/gfp.h
> > 2007-11-19 19:28:55.000000000 +0000
> > @@ -175,7 +175,6 @@ FASTCALL(__alloc_pages(gfp_t, unsigned i
> > extern struct page *
> > FASTCALL(__alloc_pages_nodemask(gfp_t, unsigned int,
> > struct zonelist *, nodemask_t *nodemask));
> > -extern nodemask_t *nodemask_thisnode(int nid, nodemask_t *nodemask);
> >
> > static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
> > unsigned int order)
> > @@ -187,13 +186,10 @@ static inline struct page *alloc_pages_n
> > if (nid < 0)
> > nid = numa_node_id();
> >
> > - /* Use a temporary nodemask for __GFP_THISNODE allocations */
> > if (unlikely(gfp_mask & __GFP_THISNODE)) {
> > - nodemask_t nodemask;
> > -
> > return __alloc_pages_nodemask(gfp_mask, order,
> > node_zonelist(nid),
> > - nodemask_thisnode(nid, &nodemask));
> > + NODE_DATA(nid)->nodemask_thisnode);
> > }
> >
> > return __alloc_pages(gfp_mask, order, node_zonelist(nid));
> > diff -rup -X /usr/src/patchset-0.6/bin//dontdiff
> > linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/mmzone.h
> > linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/mmzone.h
> > --- linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/mmzone.h
> > 2007-11-19 19:27:15.000000000 +0000
> > +++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/mmzone.h
> > 2007-11-19 19:28:55.000000000 +0000
> > @@ -519,6 +519,9 @@ typedef struct pglist_data {
> > struct zone node_zones[MAX_NR_ZONES];
> > struct zonelist node_zonelist;
> > int nr_zones;
> > +
> > + /* nodemask suitable for __GFP_THISNODE */
> > + nodemask_t *nodemask_thisnode;
> > #ifdef CONFIG_FLAT_NODE_MEM_MAP
> > struct page *node_mem_map;
> > #endif
> > diff -rup -X /usr/src/patchset-0.6/bin//dontdiff
> > linux-2.6.24-rc2-mm1-040_use_one_zonelist/mm/page_alloc.c
> > linux-2.6.24-rc2-mm1-045_use_static_nodemask/mm/page_alloc.c
> > --- linux-2.6.24-rc2-mm1-040_use_one_zonelist/mm/page_alloc.c
> > 2007-11-19 19:27:15.000000000 +0000
> > +++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/mm/page_alloc.c
> > 2007-11-19 19:28:55.000000000 +0000
> > @@ -1695,28 +1695,36 @@ got_pg:
> > }
> >
> > /* Creates a nodemask suitable for GFP_THISNODE allocations */
> > -nodemask_t *nodemask_thisnode(int nid, nodemask_t *nodemask)
> > +static inline void alloc_node_nodemask_thisnode(pg_data_t *pgdat)
> > {
> > - nodes_clear(*nodemask);
> > - node_set(nid, *nodemask);
> > + nodemask_t *nodemask_thisnode;
> >
> > - return nodemask;
> > + /* Only a machine with multiple nodes needs the nodemask */
> > + if (!NUMA_BUILD || num_online_nodes() == 1)
> > + return;
> > +
> > + /* Allocate the nodemask. Serious if it fails, but not world ending */
> > + nodemask_thisnode = alloc_bootmem_node(pgdat, sizeof(nodemask_t));
> > + if (!nodemask_thisnode) {
> > + printk(KERN_WARNING
> > + "thisnode nodemask allocation failed."
> > + "There may be sub-optimal NUMA placement.\n");
> > + return;
> > + }
> > +
> > + /* Initialise the nodemask to only cover the current node */
> > + nodes_clear(*nodemask_thisnode);
> > + node_set(pgdat->node_id, *nodemask_thisnode);
> > + pgdat->nodemask_thisnode = nodemask_thisnode;
> > }
> >
> > struct page * fastcall
> > __alloc_pages(gfp_t gfp_mask, unsigned int order,
> > struct zonelist *zonelist)
> > {
> > - /*
> > - * Use a temporary nodemask for __GFP_THISNODE allocations. If the
> > - * cost of allocating on the stack or the stack usage becomes
> > - * noticable, allocate the nodemasks per node at boot or compile time
> > - */
> > if (unlikely(gfp_mask & __GFP_THISNODE)) {
> > - nodemask_t nodemask;
> > -
> > - return __alloc_pages_internal(gfp_mask, order,
> > - zonelist, nodemask_thisnode(numa_node_id(), &nodemask));
> > + return __alloc_pages_internal(gfp_mask, order, zonelist,
> > + NODE_DATA(numa_node_id())->nodemask_thisnode);
> > }
> >
> > return __alloc_pages_internal(gfp_mask, order, zonelist, NULL);
> > @@ -3501,6 +3509,7 @@ void __meminit free_area_init_node(int n
> > calculate_node_totalpages(pgdat, zones_size, zholes_size);
> >
> > alloc_node_mem_map(pgdat);
> > + alloc_node_nodemask_thisnode(pgdat);
> >
> > free_area_init_core(pgdat, zones_size, zholes_size);
> > }
> >
>
--
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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