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Date: Mon, 19 Mar 2007 18:06:02 -0700 (PDT)
From: Christoph Lameter <clameter@....com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [QUICKLIST 1/5] Quicklists for page table pages V3
On Mon, 19 Mar 2007, Andrew Morton wrote:
> > +
> > +#ifdef CONFIG_QUICKLIST
> > +
> > +#ifndef CONFIG_NR_QUICK
> > +#define CONFIG_NR_QUICK 1
> > +#endif
>
> No, please don't define config items like this. Do it in Kconfig.
They can be set up in the arch specific Kconfig. Ok. I moved the
#ifndef .. #endif into mm/Kconfig.
> These guys seem to have multiple callsites for ia64 at least and probably
> would benefit from being uninlined.
Then they would no longer be optimizable. Right now one can compile out
the constructor / destructor support and provide a constant list number
as well as constant gfp masks. This can be very small and benefit
tremendously from inlining.
Many arches do not need some features and there are only a few call
sites.
> > +void quicklist_check(int nr, void (*dtor)(void *));
> > +unsigned long quicklist_total_size(void);
> > +
> > +#else
> > +void quicklist_check(int nr, void (*dtor)(void *))
> > +{
> > +}
> > +
> > +unsigned long quicklist_total_size(void)
> > +{
> > + return 0;
> > +}
> > +#endif
>
> That obviouslty won't link and wasn't tested. Making these static inline
> will help.
Hmmm... We could drop these conmpletely. If an arch does not use
quicklists then they should not be calling these.
> > +#include <linux/module.h>
> > +#include <linux/quicklist.h>
> > +
> > +DEFINE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];
>
> If we uninline those big inlines, this can perhaps be made static.
Yeah but we want the inlines.
>
> > +#define MIN_PAGES 25
> > +#define MAX_FREES_PER_PASS 16
> > +#define FRACTION_OF_NODE_MEM 16
>
> Are these constants optimal for all architectures?
I added them as parameters to quicklist_trim so that an arch
can specify their own settings.
> > + return min(pages_to_free, (long)MAX_FREES_PER_PASS);
> > +}
>
> min_t and max_t are the standard way of avoiding that warning. Or stick a
> UL on the constants (which is probably better).
We do not need those since the constants are now parameters.
>
> > +void quicklist_check(int nr, void (*dtor)(void *))
> > +{
> > + long pages_to_free;
> > + struct quicklist *q;
> > +
> > + q = &get_cpu_var(quicklist)[nr];
> > + if (q->nr_pages > MIN_PAGES) {
> > + pages_to_free = min_pages_to_free(q);
> > +
> > + while (pages_to_free > 0) {
> > + void *p = quicklist_alloc(nr, 0, NULL);
> > +
> > + if (dtor)
> > + dtor(p);
> > + free_page((unsigned long)p);
> > + pages_to_free--;
> > + }
> > + }
> > + put_cpu_var(quicklist);
> > +}
>
> The use of a literal 0 as a gfp_t is a bit ugly. I assume that we don't
> care because we should never actually call into the page allocator for this
> caller. But it's not terribly clear because there is no commentary
> describing what this function is supposed to do.
Right. Will add comments.
> The name foo_check() is unfortunate: it implies that the function checks
> something (ie: has no side-effects). But this function _does_ change
> things and perhaps should be called quicklist_trim() or something like
> that.
Tradition. Dave initially named it check_pgt_cache it seems.
> This function lacks any commentary, but I was able to work it out. I
> think. Some nice comments would be, umm, nice.
ok. Here is a fixup patch:
Index: linux-2.6.21-rc3-mm2/include/linux/quicklist.h
===================================================================
--- linux-2.6.21-rc3-mm2.orig/include/linux/quicklist.h 2007-03-19 17:41:42.000000000 -0700
+++ linux-2.6.21-rc3-mm2/include/linux/quicklist.h 2007-03-19 17:47:34.000000000 -0700
@@ -13,10 +13,6 @@
#ifdef CONFIG_QUICKLIST
-#ifndef CONFIG_NR_QUICK
-#define CONFIG_NR_QUICK 1
-#endif
-
struct quicklist {
void *page;
int nr_pages;
@@ -77,18 +73,11 @@ static inline void quicklist_free(int nr
put_cpu_var(quicklist);
}
-void quicklist_check(int nr, void (*dtor)(void *));
-unsigned long quicklist_total_size(void);
+void quicklist_trim(int nr, void (*dtor)(void *),
+ unsigned long min_pages, unsigned long max_free);
-#else
-void quicklist_check(int nr, void (*dtor)(void *))
-{
-}
+unsigned long quicklist_total_size(void);
-unsigned long quicklist_total_size(void)
-{
- return 0;
-}
#endif
#endif /* LINUX_QUICKLIST_H */
Index: linux-2.6.21-rc3-mm2/mm/Kconfig
===================================================================
--- linux-2.6.21-rc3-mm2.orig/mm/Kconfig 2007-03-19 17:41:42.000000000 -0700
+++ linux-2.6.21-rc3-mm2/mm/Kconfig 2007-03-19 17:42:49.000000000 -0700
@@ -220,3 +220,7 @@ config DEBUG_READAHEAD
Say N for production servers.
+config NR_QUICK
+ depends on QUICKLIST
+ default 1
+
Index: linux-2.6.21-rc3-mm2/mm/quicklist.c
===================================================================
--- linux-2.6.21-rc3-mm2.orig/mm/quicklist.c 2007-03-19 17:41:42.000000000 -0700
+++ linux-2.6.21-rc3-mm2/mm/quicklist.c 2007-03-19 17:53:45.000000000 -0700
@@ -21,39 +21,46 @@
DEFINE_PER_CPU(struct quicklist, quicklist)[CONFIG_NR_QUICK];
-#define MIN_PAGES 25
-#define MAX_FREES_PER_PASS 16
#define FRACTION_OF_NODE_MEM 16
-static unsigned long max_pages(void)
+static unsigned long max_pages(unsigned long min_pages)
{
unsigned long node_free_pages, max;
node_free_pages = node_page_state(numa_node_id(),
NR_FREE_PAGES);
max = node_free_pages / FRACTION_OF_NODE_MEM;
- return max(max, (unsigned long)MIN_PAGES);
+ return max(max, min_pages);
}
-static long min_pages_to_free(struct quicklist *q)
+static long min_pages_to_free(struct quicklist *q,
+ unsigned long min_pages, long max_free)
{
long pages_to_free;
- pages_to_free = q->nr_pages - max_pages();
+ pages_to_free = q->nr_pages - max_pages(min_pages);
- return min(pages_to_free, (long)MAX_FREES_PER_PASS);
+ return min(pages_to_free, max_free);
}
-void quicklist_check(int nr, void (*dtor)(void *))
+/*
+ * Trim down the number of pages in the quicklist
+ */
+void quicklist_trim(int nr, void (*dtor)(void *),
+ unsigned long min_pages, unsigned long max_free)
{
long pages_to_free;
struct quicklist *q;
q = &get_cpu_var(quicklist)[nr];
- if (q->nr_pages > MIN_PAGES) {
- pages_to_free = min_pages_to_free(q);
+ if (q->nr_pages > min_pages) {
+ pages_to_free = min_pages_to_free(q, min_pages, max_free);
while (pages_to_free > 0) {
+ /*
+ * We pass a gfp_t of 0 to quicklist_alloc here
+ * because we will never call into the page allocator.
+ */
void *p = quicklist_alloc(nr, 0, NULL);
if (dtor)
Index: linux-2.6.21-rc3-mm2/arch/i386/mm/pgtable.c
===================================================================
--- linux-2.6.21-rc3-mm2.orig/arch/i386/mm/pgtable.c 2007-03-19 17:42:44.000000000 -0700
+++ linux-2.6.21-rc3-mm2/arch/i386/mm/pgtable.c 2007-03-19 17:42:49.000000000 -0700
@@ -299,6 +299,6 @@ void pgd_free(pgd_t *pgd)
void check_pgt_cache(void)
{
- quicklist_check(QUICK_PGD, pgd_dtor);
- quicklist_check(QUICK_PMD, NULL);
+ quicklist_trim(QUICK_PGD, pgd_dtor, 25, 16);
+ quicklist_trim(QUICK_PMD, NULL, 25, 16);
}
Index: linux-2.6.21-rc3-mm2/include/asm-x86_64/pgalloc.h
===================================================================
--- linux-2.6.21-rc3-mm2.orig/include/asm-x86_64/pgalloc.h 2007-03-19 17:42:46.000000000 -0700
+++ linux-2.6.21-rc3-mm2/include/asm-x86_64/pgalloc.h 2007-03-19 17:42:49.000000000 -0700
@@ -121,7 +121,7 @@ static inline void pte_free(struct page
static inline void check_pgt_cache(void)
{
- quicklist_check(QUICK_PGD, pgd_dtor);
- quicklist_check(QUICK_PT, NULL);
+ quicklist_trim(QUICK_PGD, pgd_dtor, 25, 16);
+ quicklist_trim(QUICK_PT, NULL, 25, 16);
}
#endif /* _X86_64_PGALLOC_H */
Index: linux-2.6.21-rc3-mm2/include/asm-sparc64/pgalloc.h
===================================================================
--- linux-2.6.21-rc3-mm2.orig/include/asm-sparc64/pgalloc.h 2007-03-19 17:42:47.000000000 -0700
+++ linux-2.6.21-rc3-mm2/include/asm-sparc64/pgalloc.h 2007-03-19 17:42:49.000000000 -0700
@@ -67,7 +67,7 @@ static inline void pte_free(struct page
static inline void check_pgt_cache(void)
{
- quicklist_check(0, NULL);
+ quicklist_trim(0, NULL, 25, 16);
}
#endif /* _SPARC64_PGALLOC_H */
Index: linux-2.6.21-rc3-mm2/include/asm-ia64/pgalloc.h
===================================================================
--- linux-2.6.21-rc3-mm2.orig/include/asm-ia64/pgalloc.h 2007-03-19 17:42:43.000000000 -0700
+++ linux-2.6.21-rc3-mm2/include/asm-ia64/pgalloc.h 2007-03-19 17:42:59.000000000 -0700
@@ -106,7 +106,7 @@ static inline void pte_free_kernel(pte_t
static inline void check_pgt_cache(void)
{
- quicklist_check(0, NULL);
+ quicklist_trim(0, NULL, 25, 16);
}
#define __pte_free_tlb(tlb, pte) pte_free(pte)
-
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