This patch
(1) eliminates the pte_chain_freelist_lock and all contention on it
(2) gives the VM the ability to recover unused pte_chain pages
Anton Blanchard has reported (1) from prior incarnations of this patch.
Craig Kulesa has reported (2) in combination with slab-on-LRU patches.
I've left OOM detection out of this patch entirely as upcoming patches
will do real OOM handling for pte_chains and all the code changed anyway.
This also removes more code than it adds:
$ diffstat ~/patches/pte_chain_slab-1
fs/proc/proc_misc.c | 6 +--
include/linux/page-flags.h | 3 -
init/main.c | 4 +-
mm/page_alloc.c | 3 -
mm/rmap.c | 82 +++++++++------------------------------------
5 files changed, 23 insertions(+), 75 deletions(-)
It only took a couple of minutes while my test machines were busy
booting anyway so it hasn't taken time away from highpte_chain.
Cheers,
Bill
===== fs/proc/proc_misc.c 1.31 vs edited =====
--- 1.31/fs/proc/proc_misc.c Tue Jul 16 14:46:30 2002
+++ edited/fs/proc/proc_misc.c Mon Jul 22 18:33:38 2002
@@ -161,8 +161,7 @@
"Dirty: %8lu kB\n"
"Writeback: %8lu kB\n"
"PageTables: %8lu kB\n"
- "PteChainTot: %8lu kB\n"
- "PteChainUsed: %8lu kB\n",
+ "ReverseMaps: %8lu\n",
K(i.totalram),
K(i.freeram),
K(i.sharedram),
@@ -179,8 +178,7 @@
K(ps.nr_dirty),
K(ps.nr_writeback),
K(ps.nr_page_table_pages),
- K(ps.nr_pte_chain_pages),
- ps.used_pte_chains_bytes >> 10
+ ps.nr_reverse_maps
);
return proc_calc_metrics(page, start, off, count, eof, len);
===== include/linux/page-flags.h 1.12 vs edited =====
--- 1.12/include/linux/page-flags.h Tue Jul 16 14:46:30 2002
+++ edited/include/linux/page-flags.h Mon Jul 22 18:33:38 2002
@@ -79,8 +79,7 @@
unsigned long nr_active; /* on active_list LRU */
unsigned long nr_inactive; /* on inactive_list LRU */
unsigned long nr_page_table_pages;
- unsigned long nr_pte_chain_pages;
- unsigned long used_pte_chains_bytes;
+ unsigned long nr_reverse_maps;
} ____cacheline_aligned_in_smp page_states[NR_CPUS];
extern void get_page_state(struct page_state *ret);
===== init/main.c 1.52 vs edited =====
--- 1.52/init/main.c Sun Jul 21 09:09:17 2002
+++ edited/init/main.c Mon Jul 22 18:33:38 2002
@@ -70,7 +70,7 @@
extern void sysctl_init(void);
extern void signals_init(void);
extern void buffer_init(void);
-
+extern void pte_chain_init(void);
extern void radix_tree_init(void);
extern void free_initmem(void);
@@ -386,7 +386,7 @@
mem_init();
kmem_cache_sizes_init();
pgtable_cache_init();
-
+ pte_chain_init();
mempages = num_physpages;
fork_init(mempages);
===== mm/page_alloc.c 1.82 vs edited =====
--- 1.82/mm/page_alloc.c Tue Jul 16 14:46:36 2002
+++ edited/mm/page_alloc.c Mon Jul 22 18:33:38 2002
@@ -566,8 +566,7 @@
ret->nr_active += ps->nr_active;
ret->nr_inactive += ps->nr_inactive;
ret->nr_page_table_pages += ps->nr_page_table_pages;
- ret->nr_pte_chain_pages += ps->nr_pte_chain_pages;
- ret->used_pte_chains_bytes += ps->used_pte_chains_bytes;
+ ret->nr_reverse_maps += ps->nr_reverse_maps;
}
}
===== mm/rmap.c 1.3 vs edited =====
--- 1.3/mm/rmap.c Tue Jul 16 14:46:30 2002
+++ edited/mm/rmap.c Mon Jul 22 18:36:51 2002
@@ -23,6 +23,8 @@
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/swapops.h>
+#include <linux/slab.h>
+#include <linux/init.h>
#include <asm/pgalloc.h>
#include <asm/rmap.h>
@@ -50,10 +52,10 @@
pte_t * ptep;
};
+static kmem_cache_t *pte_chain_cache;
static inline struct pte_chain * pte_chain_alloc(void);
static inline void pte_chain_free(struct pte_chain *, struct pte_chain *,
struct page *);
-static void alloc_new_pte_chains(void);
/**
* page_referenced - test if the page was referenced
@@ -148,6 +151,7 @@
}
pte_chain_unlock(page);
+ inc_page_state(nr_reverse_maps);
}
/**
@@ -208,9 +212,9 @@
#endif
out:
+ dec_page_state(nr_reverse_maps);
pte_chain_unlock(page);
return;
-
}
/**
@@ -355,27 +359,6 @@
** functions.
**/
-struct pte_chain * pte_chain_freelist;
-spinlock_t pte_chain_freelist_lock = SPIN_LOCK_UNLOCKED;
-
-/* Maybe we should have standard ops for singly linked lists ... - Rik */
-static inline void pte_chain_push(struct pte_chain * pte_chain)
-{
- pte_chain->ptep = NULL;
- pte_chain->next = pte_chain_freelist;
- pte_chain_freelist = pte_chain;
-}
-
-static inline struct pte_chain * pte_chain_pop(void)
-{
- struct pte_chain *pte_chain;
-
- pte_chain = pte_chain_freelist;
- pte_chain_freelist = pte_chain->next;
- pte_chain->next = NULL;
-
- return pte_chain;
-}
/**
* pte_chain_free - free pte_chain structure
@@ -391,15 +374,12 @@
static inline void pte_chain_free(struct pte_chain * pte_chain,
struct pte_chain * prev_pte_chain, struct page * page)
{
- mod_page_state(used_pte_chains_bytes, -sizeof(struct pte_chain));
if (prev_pte_chain)
prev_pte_chain->next = pte_chain->next;
else if (page)
page->pte.chain = pte_chain->next;
- spin_lock(&pte_chain_freelist_lock);
- pte_chain_push(pte_chain);
- spin_unlock(&pte_chain_freelist_lock);
+ kmem_cache_free(pte_chain_cache, pte_chain);
}
/**
@@ -409,47 +389,20 @@
* pte_chain structures as required.
* Caller needs to hold the page's pte_chain_lock.
*/
-static inline struct pte_chain * pte_chain_alloc()
+static inline struct pte_chain *pte_chain_alloc(void)
{
- struct pte_chain * pte_chain;
-
- spin_lock(&pte_chain_freelist_lock);
-
- /* Allocate new pte_chain structs as needed. */
- if (!pte_chain_freelist)
- alloc_new_pte_chains();
-
- /* Grab the first pte_chain from the freelist. */
- pte_chain = pte_chain_pop();
-
- spin_unlock(&pte_chain_freelist_lock);
-
- mod_page_state(used_pte_chains_bytes, sizeof(struct pte_chain));
- return pte_chain;
+ return kmem_cache_alloc(pte_chain_cache, GFP_ATOMIC);
}
-/**
- * alloc_new_pte_chains - convert a free page to pte_chain structures
- *
- * Grabs a free page and converts it to pte_chain structures. We really
- * should pre-allocate these earlier in the pagefault path or come up
- * with some other trick.
- *
- * Note that we cannot use the slab cache because the pte_chain structure
- * is way smaller than the minimum size of a slab cache allocation.
- * Caller needs to hold the pte_chain_freelist_lock
- */
-static void alloc_new_pte_chains()
+void __init pte_chain_init(void)
{
- struct pte_chain * pte_chain = (void *) get_zeroed_page(GFP_ATOMIC);
- int i = PAGE_SIZE / sizeof(struct pte_chain);
+ pte_chain_cache = kmem_cache_create( "pte_chain",
+ sizeof(struct pte_chain),
+ 0,
+ 0,
+ NULL,
+ NULL);
- if (pte_chain) {
- inc_page_state(nr_pte_chain_pages);
- for (; i-- > 0; pte_chain++)
- pte_chain_push(pte_chain);
- } else {
- /* Yeah yeah, I'll fix the pte_chain allocation ... */
- panic("Fix pte_chain allocation, you lazy bastard!\n");
- }
+ if (!pte_chain_cache)
+ panic("failed to create pte_chain cache!\n");
}
-
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