Re: [RFC][PATCH][3/4] Add reclaim support
From: Balbir Singh
Date: Mon Feb 19 2007 - 05:52:44 EST
Andrew Morton wrote:
On Mon, 19 Feb 2007 12:20:42 +0530 Balbir Singh <balbir@xxxxxxxxxx> wrote:
This patch reclaims pages from a container when the container limit is hit.
The executable is oom'ed only when the container it is running in, is overlimit
and we could not reclaim any pages belonging to the container
A parameter called pushback, controls how much memory is reclaimed when the
limit is hit. It should be easy to expose this knob to user space, but
currently it is hard coded to 20% of the total limit of the container.
isolate_lru_pages() has been modified to isolate pages belonging to a
particular container, so that reclaim code will reclaim only container
pages. For shared pages, reclaim does not unmap all mappings of the page,
it only unmaps those mappings that are over their limit. This ensures
that other containers are not penalized while reclaiming shared pages.
Parallel reclaim per container is not allowed. Each controller has a wait
queue that ensures that only one task per control is running reclaim on
that container.
...
--- linux-2.6.20/include/linux/rmap.h~memctlr-reclaim-on-limit 2007-02-18 23:29:14.000000000 +0530
+++ linux-2.6.20-balbir/include/linux/rmap.h 2007-02-18 23:29:14.000000000 +0530
@@ -90,7 +90,15 @@ static inline void page_dup_rmap(struct
* Called from mm/vmscan.c to handle paging out
*/
int page_referenced(struct page *, int is_locked);
-int try_to_unmap(struct page *, int ignore_refs);
+int try_to_unmap(struct page *, int ignore_refs, void *container);
+#ifdef CONFIG_CONTAINER_MEMCTLR
+bool page_in_container(struct page *page, struct zone *zone, void *container);
+#else
+static inline bool page_in_container(struct page *page, struct zone *zone, void *container)
+{
+ return true;
+}
+#endif /* CONFIG_CONTAINER_MEMCTLR */
/*
* Called from mm/filemap_xip.c to unmap empty zero page
@@ -118,7 +126,8 @@ int page_mkclean(struct page *);
#define anon_vma_link(vma) do {} while (0)
#define page_referenced(page,l) TestClearPageReferenced(page)
-#define try_to_unmap(page, refs) SWAP_FAIL
+#define try_to_unmap(page, refs, container) SWAP_FAIL
+#define page_in_container(page, zone, container) true
I spy a compile error.
The static-inline version looks nicer.
I will compile with the feature turned off and double check. I'll
also convert it to a static inline function.
static inline int page_mkclean(struct page *page)
{
diff -puN include/linux/swap.h~memctlr-reclaim-on-limit include/linux/swap.h
--- linux-2.6.20/include/linux/swap.h~memctlr-reclaim-on-limit 2007-02-18 23:29:14.000000000 +0530
+++ linux-2.6.20-balbir/include/linux/swap.h 2007-02-18 23:29:14.000000000 +0530
@@ -188,6 +188,10 @@ extern void swap_setup(void);
/* linux/mm/vmscan.c */
extern unsigned long try_to_free_pages(struct zone **, gfp_t);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
+#ifdef CONFIG_CONTAINER_MEMCTLR
+extern unsigned long memctlr_shrink_mapped_memory(unsigned long nr_pages,
+ void *container);
+#endif
Usually one doesn't need to put ifdefs around the declaration like this.
If the function doesn't exist and nobody calls it, we're fine. If someone
_does_ call it, we'll find out the error at link-time.
Sure, sounds good. I'll get rid of the #ifdefs.
+/*
+ * checks if the mm's container and scan control passed container match, if
+ * so, is the container over it's limit. Returns 1 if the container is above
+ * its limit.
+ */
+int memctlr_mm_overlimit(struct mm_struct *mm, void *sc_cont)
+{
+ struct container *cont;
+ struct memctlr *mem;
+ long usage, limit;
+ int ret = 1;
+
+ if (!sc_cont)
+ goto out;
+
+ read_lock(&mm->container_lock);
+ cont = mm->container;
+
+ /*
+ * Regular reclaim, let it proceed as usual
+ */
+ if (!sc_cont)
+ goto out;
+
+ ret = 0;
+ if (cont != sc_cont)
+ goto out;
+
+ mem = memctlr_from_cont(cont);
+ usage = atomic_long_read(&mem->counter.usage);
+ limit = atomic_long_read(&mem->counter.limit);
+ if (limit && (usage > limit))
+ ret = 1;
+out:
+ read_unlock(&mm->container_lock);
+ return ret;
+}
hm, I wonder how much additional lock traffic all this adds.
It's a read_lock() and most of the locks are read_locks
which allow for concurrent access, until the container
changes or goes away
int memctlr_mm_init(struct mm_struct *mm)
{
mm->counter = kmalloc(sizeof(struct res_counter), GFP_KERNEL);
@@ -77,6 +125,46 @@ void memctlr_mm_assign_container(struct
write_unlock(&mm->container_lock);
}
+static int memctlr_check_and_reclaim(struct container *cont, long usage,
+ long limit)
+{
+ unsigned long nr_pages = 0;
+ unsigned long nr_reclaimed = 0;
+ int retries = nr_retries;
+ int ret = 1;
+ struct memctlr *mem;
+
+ mem = memctlr_from_cont(cont);
+ spin_lock(&mem->lock);
+ while ((retries-- > 0) && limit && (usage > limit)) {
+ if (mem->reclaim_in_progress) {
+ spin_unlock(&mem->lock);
+ wait_event(mem->wq, !mem->reclaim_in_progress);
+ spin_lock(&mem->lock);
+ } else {
+ if (!nr_pages)
+ nr_pages = (pushback * limit) / 100;
+ mem->reclaim_in_progress = true;
+ spin_unlock(&mem->lock);
+ nr_reclaimed += memctlr_shrink_mapped_memory(nr_pages,
+ cont);
+ spin_lock(&mem->lock);
+ mem->reclaim_in_progress = false;
+ wake_up_all(&mem->wq);
+ }
+ /*
+ * Resample usage and limit after reclaim
+ */
+ usage = atomic_long_read(&mem->counter.usage);
+ limit = atomic_long_read(&mem->counter.limit);
+ }
+ spin_unlock(&mem->lock);
+
+ if (limit && (usage > limit))
+ ret = 0;
+ return ret;
+}
This all looks a bit racy. And that's common in memory reclaim. We just
have to ensure that when the race happens, we do reasonable things.
I suspect the locking in here could simply be removed.
The locking is mostly to ensure that tasks belonging to the same container
see a consistent value of reclaim_in_progress. I'll see if the locking
can be simplified or simply removed.
@@ -66,6 +67,9 @@ struct scan_control {
int swappiness;
int all_unreclaimable;
+
+ void *container; /* Used by containers for reclaiming */
+ /* pages when the limit is exceeded */
};
eww. Why void*?
I did not want to expose struct container in mm/vmscan.c. An additional
thought was that no matter what container goes in the field would be
useful for reclaim.
+#ifdef CONFIG_CONTAINER_MEMCTLR
+/*
+ * Try to free `nr_pages' of memory, system-wide, and return the number of
+ * freed pages.
+ * Modelled after shrink_all_memory()
+ */
+unsigned long memctlr_shrink_mapped_memory(unsigned long nr_pages, void *container)
80-columns, please.
I'll fix this.
+{
+ unsigned long ret = 0;
+ int pass;
+ unsigned long nr_total_scanned = 0;
+
+ struct scan_control sc = {
+ .gfp_mask = GFP_KERNEL,
+ .may_swap = 0,
+ .swap_cluster_max = nr_pages,
+ .may_writepage = 1,
+ .swappiness = vm_swappiness,
+ .container = container,
+ .may_swap = 1,
+ .swappiness = 100,
+ };
swappiness got initialised twice.
I should have caught that earlier. Thanks for spotting this.
I'll fix it.
+ /*
+ * We try to shrink LRUs in 3 passes:
+ * 0 = Reclaim from inactive_list only
+ * 1 = Reclaim mapped (normal reclaim)
+ * 2 = 2nd pass of type 1
+ */
+ for (pass = 0; pass < 3; pass++) {
+ int prio;
+
+ for (prio = DEF_PRIORITY; prio >= 0; prio--) {
+ unsigned long nr_to_scan = nr_pages - ret;
+
+ sc.nr_scanned = 0;
+ ret += shrink_all_zones(nr_to_scan, prio,
+ pass, 1, &sc);
+ if (ret >= nr_pages)
+ goto out;
+
+ nr_total_scanned += sc.nr_scanned;
+ if (sc.nr_scanned && prio < DEF_PRIORITY - 2)
+ congestion_wait(WRITE, HZ / 10);
+ }
+ }
+out:
+ return ret;
+}
+#endif
--
Warm Regards,
Balbir Singh
-
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