Re: [PATCH] RSS Container, make page_referenced() container aware

Balbir Singh
2007-04-27T11:12:00Z

Pavel Emelianov wrote:
> Balbir Singh wrote:
>> Hi, Pavel,
>>
>> This patch should help with the shared page issue of one container
>> holding shared pages in a another container (the container that
>> brought in the page -- by first touch) hostage.
>
> The shared pages accounting is tricky.
> Actually we planned not to do it right now, but later,
> when (if) this will be accepted and we'll move forward
> to the fractions accounting.
>

Yes, but this patch ensures that we do not hit bottle necks
when pages are shared

>> ------------------------------------------------------------------------
>>
>>
>>
>> Make page_referenced() container aware. Without this patch, page_referenced()
>> can cause a page to be skipped while reclaiming pages. This patch
>> ensures that other containers do not hold pages in a particular container
>> hostage. It is required to ensure that shared pages are freed from a container
>> when they are not actively referenced from the container that brought
>> them in
>>
>> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
>> ---
>>
>> include/linux/rmap.h | 5 +++--
>> mm/rmap.c | 26 ++++++++++++++++++++------
>> mm/vmscan.c | 4 ++--
>> 3 files changed, 25 insertions(+), 10 deletions(-)
>>
>> diff -puN mm/vmscan.c~rss-implement-per-container-page-referenced mm/vmscan.c
>> --- linux-2.6.20/mm/vmscan.c~rss-implement-per-container-page-referenced 2007-04-26 23:28:44.000000000 +0530
>> +++ linux-2.6.20-balbir/mm/vmscan.c 2007-04-27 00:04:38.000000000 +0530
>> @@ -489,7 +489,7 @@ static unsigned long shrink_page_list(st
>> if (PageWriteback(page))
>> goto keep_locked;
>>
>> - referenced = page_referenced(page, 1);
>> + referenced = page_referenced(page, 1, sc->cnt);
>> /* In active use or really unfreeable? Activate it. */
>> if (referenced && page_mapping_inuse(page))
>> goto activate_locked;
>> @@ -852,7 +852,7 @@ force_reclaim_mapped:
>> if (page_mapped(page)) {
>> if (!reclaim_mapped ||
>> (total_swap_pages == 0 && PageAnon(page)) ||
>> - page_referenced(page, 0)) {
>> + page_referenced(page, 0, sc->cnt)) {
>> list_add(&page->lru, &l_active);
>> continue;
>> }
>> diff -puN mm/rmap.c~rss-implement-per-container-page-referenced mm/rmap.c
>> --- linux-2.6.20/mm/rmap.c~rss-implement-per-container-page-referenced 2007-04-26 23:28:44.000000000 +0530
>> +++ linux-2.6.20-balbir/mm/rmap.c 2007-04-26 23:33:41.000000000 +0530
>> @@ -318,7 +318,7 @@ out:
>> return referenced;
>> }
>>
>> -static int page_referenced_anon(struct page *page)
>> +static int page_referenced_anon(struct page *page, struct rss_container *cnt)
>> {
>> unsigned int mapcount;
>> struct anon_vma *anon_vma;
>> @@ -331,6 +331,13 @@ static int page_referenced_anon(struct p
>>
>> mapcount = page_mapcount(page);
>> list_for_each_entry(vma, &anon_vma->head, anon_vma_node) {
>> + /*
>> + * If we are reclaiming on behalf of a container, skip
>> + * counting on behalf of references from different
>> + * containers
>> + */
>> + if (cnt && (vma->vm_mm->rss_container != cnt))
>> + continue;
>
> An #ifdef missed - mm->rss_container makes sense with
> the CONFIG_RSS_COUNTAINER set only.

Good catch. I'll fix it!

>
>> referenced += page_referenced_one(page, vma, &mapcount);
>> if (!mapcount)
>> break;
>> @@ -350,7 +357,7 @@ static int page_referenced_anon(struct p
>> *
>> * This function is only called from page_referenced for object-based pages.
>> */
>> -static int page_referenced_file(struct page *page)
>> +static int page_referenced_file(struct page *page, struct rss_container *cnt)
>> {
>> unsigned int mapcount;
>> struct address_space *mapping = page->mapping;
>> @@ -383,6 +390,13 @@ static int page_referenced_file(struct p
>> mapcount = page_mapcount(page);
>>
>> vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
>> + /*
>> + * If we are reclaiming on behalf of a container, skip
>> + * counting on behalf of references from different
>> + * containers
>> + */
>> + if (cnt && (vma->vm_mm->rss_container != cnt))
>> + continue;
>> if ((vma->vm_flags & (VM_LOCKED|VM_MAYSHARE))
>> == (VM_LOCKED|VM_MAYSHARE)) {
>> referenced++;
>> @@ -405,7 +419,7 @@ static int page_referenced_file(struct p
>> * Quick test_and_clear_referenced for all mappings to a page,
>> * returns the number of ptes which referenced the page.
>> */
>> -int page_referenced(struct page *page, int is_locked)
>> +int page_referenced(struct page *page, int is_locked, struct rss_container *cnt)
>> {
>> int referenced = 0;
>>
>> @@ -417,14 +431,14 @@ int page_referenced(struct page *page, i
>>
>> if (page_mapped(page) && page->mapping) {
>> if (PageAnon(page))
>> - referenced += page_referenced_anon(page);
>> + referenced += page_referenced_anon(page, cnt);
>> else if (is_locked)
>> - referenced += page_referenced_file(page);
>> + referenced += page_referenced_file(page, cnt);
>> else if (TestSetPageLocked(page))
>> referenced++;
>> else {
>> if (page->mapping)
>> - referenced += page_referenced_file(page);
>> + referenced += page_referenced_file(page, cnt);
>> unlock_page(page);
>> }
>> }
>> diff -puN include/linux/rmap.h~rss-implement-per-container-page-referenced include/linux/rmap.h
>> --- linux-2.6.20/include/linux/rmap.h~rss-implement-per-container-page-referenced 2007-04-26 23:28:44.000000000 +0530
>> +++ linux-2.6.20-balbir/include/linux/rmap.h 2007-04-26 23:29:31.000000000 +0530
>> @@ -8,6 +8,7 @@
>> #include <linux/slab.h>
>> #include <linux/mm.h>
>> #include <linux/spinlock.h>
>> +#include <linux/rss_container.h>
>>
>> /*
>> * The anon_vma heads a list of private "related" vmas, to scan if
>> @@ -93,7 +94,7 @@ 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 page_referenced(struct page *, int is_locked, struct rss_container *cnt);
>> int try_to_unmap(struct page *, int ignore_refs);
>>
>> /*
>> @@ -121,7 +122,7 @@ int page_mkclean(struct page *);
>> #define anon_vma_prepare(vma) (0)
>> #define anon_vma_link(vma) do {} while (0)
>>
>> -#define page_referenced(page,l) TestClearPageReferenced(page)
>> +#define page_referenced(page,l,cnt) TestClearPageReferenced(page)
>> #define try_to_unmap(page, refs) SWAP_FAIL
>>
>> static inline int page_mkclean(struct page *page)
>> _
>

--
Thanks,
Balbir Singh
Linux Technology Center
IBM, ISTL