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authorYafang Shao <laoar.shao@gmail.com>2020-10-14 02:51:47 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-14 04:38:29 +0300
commiteb1d7a65f08a52dfb828bf45b4ead7f617c64047 (patch)
tree8817546462fcbf644e239f04bc1f3c070c4212a1 /mm/truncate.c
parent27a83a609b3b39b0a4ec6c75050b1183d7c302db (diff)
downloadlinux-eb1d7a65f08a52dfb828bf45b4ead7f617c64047.tar.xz
mm, fadvise: improve the expensive remote LRU cache draining after FADV_DONTNEED
Our users reported that there're some random latency spikes when their RT process is running. Finally we found that latency spike is caused by FADV_DONTNEED. Which may call lru_add_drain_all() to drain LRU cache on remote CPUs, and then waits the per-cpu work to complete. The wait time is uncertain, which may be tens millisecond. That behavior is unreasonable, because this process is bound to a specific CPU and the file is only accessed by itself, IOW, there should be no pagecache pages on a per-cpu pagevec of a remote CPU. That unreasonable behavior is partially caused by the wrong comparation of the number of invalidated pages and the number of the target. For example, if (count < (end_index - start_index + 1)) The count above is how many pages were invalidated in the local CPU, and (end_index - start_index + 1) is how many pages should be invalidated. The usage of (end_index - start_index + 1) is incorrect, because they are virtual addresses, which may not mapped to pages. Besides that, there may be holes between start and end. So we'd better check whether there are still pages on per-cpu pagevec after drain the local cpu, and then decide whether or not to call lru_add_drain_all(). After I applied it with a hotfix to our production environment, most of the lru_add_drain_all() can be avoided. Suggested-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Link: https://lkml.kernel.org/r/20200923133318.14373-1-laoar.shao@gmail.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/truncate.c')
-rw-r--r--mm/truncate.c58
1 files changed, 40 insertions, 18 deletions
diff --git a/mm/truncate.c b/mm/truncate.c
index dd9ebc1da356..6bbe0f0b3ce9 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -528,23 +528,8 @@ void truncate_inode_pages_final(struct address_space *mapping)
}
EXPORT_SYMBOL(truncate_inode_pages_final);
-/**
- * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
- * @mapping: the address_space which holds the pages to invalidate
- * @start: the offset 'from' which to invalidate
- * @end: the offset 'to' which to invalidate (inclusive)
- *
- * This function only removes the unlocked pages, if you want to
- * remove all the pages of one inode, you must call truncate_inode_pages.
- *
- * invalidate_mapping_pages() will not block on IO activity. It will not
- * invalidate pages which are dirty, locked, under writeback or mapped into
- * pagetables.
- *
- * Return: the number of the pages that were invalidated
- */
-unsigned long invalidate_mapping_pages(struct address_space *mapping,
- pgoff_t start, pgoff_t end)
+unsigned long __invalidate_mapping_pages(struct address_space *mapping,
+ pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
{
pgoff_t indices[PAGEVEC_SIZE];
struct pagevec pvec;
@@ -610,8 +595,13 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
* Invalidation is a hint that the page is no longer
* of interest and try to speed up its reclaim.
*/
- if (!ret)
+ if (!ret) {
deactivate_file_page(page);
+ /* It is likely on the pagevec of a remote CPU */
+ if (nr_pagevec)
+ (*nr_pagevec)++;
+ }
+
if (PageTransHuge(page))
put_page(page);
count += ret;
@@ -623,8 +613,40 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
}
return count;
}
+
+/**
+ * invalidate_mapping_pages - Invalidate all the unlocked pages of one inode
+ * @mapping: the address_space which holds the pages to invalidate
+ * @start: the offset 'from' which to invalidate
+ * @end: the offset 'to' which to invalidate (inclusive)
+ *
+ * This function only removes the unlocked pages, if you want to
+ * remove all the pages of one inode, you must call truncate_inode_pages.
+ *
+ * invalidate_mapping_pages() will not block on IO activity. It will not
+ * invalidate pages which are dirty, locked, under writeback or mapped into
+ * pagetables.
+ *
+ * Return: the number of the pages that were invalidated
+ */
+unsigned long invalidate_mapping_pages(struct address_space *mapping,
+ pgoff_t start, pgoff_t end)
+{
+ return __invalidate_mapping_pages(mapping, start, end, NULL);
+}
EXPORT_SYMBOL(invalidate_mapping_pages);
+/**
+ * This helper is similar with the above one, except that it accounts for pages
+ * that are likely on a pagevec and count them in @nr_pagevec, which will used by
+ * the caller.
+ */
+void invalidate_mapping_pagevec(struct address_space *mapping,
+ pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)
+{
+ __invalidate_mapping_pages(mapping, start, end, nr_pagevec);
+}
+
/*
* This is like invalidate_complete_page(), except it ignores the page's
* refcount. We do this because invalidate_inode_pages2() needs stronger