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Date: Sun, 09 Dec 2012 23:57:27 +0800
From: xtu4 <xiaobing.tu@...el.com>
To: linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
linux-mm@...ck.org, di.zhang@...el.com,
xtu4 <xiaobing.tu@...el.com>
Subject: [PATCH] improve read ahead in kernel
Subject: [PATCH] when system in low memory scenario, imaging there is a mp3
play, or video play, we need to read mp3 or video file
from memory to page cache,but when system lack of memory,
page cache of mp3 or video file will be reclaimed.once read
in memory, then reclaimed, it will cause audio or video
glitch,and it will increase the io operation at the same
time.
Signed-off-by: xiaobing tu <xiaobing.tu@...el.com>
---
include/linux/mm_types.h | 4 ++++
mm/Kconfig | 6 ++++++
mm/filemap.c | 4 ++++
mm/readahead.c | 20 +++++++++++++++++---
mm/vmscan.c | 10 ++++++++--
5 files changed, 39 insertions(+), 5 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5b42f1b..541864d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -149,6 +149,10 @@ struct page {
*/
void *shadow;
#endif
+#ifdef CONFIG_LOWMEMORY_READAHEAD
+ unsigned int ioprio;
+#endif
+
}
/*
* If another subsystem starts using the double word pairing for atomic
diff --git a/mm/Kconfig b/mm/Kconfig
index e338407..dade8d3 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -140,6 +140,12 @@ config ARCH_DISCARD_MEMBLOCK
config NO_BOOTMEM
boolean
+# improve readahead in low memory scenario
+config LOWMEMORY_READAHEAD
+ bool "improve readahead in low memory scenario"
+ depends on (IA64 || X86)
+
+
# eventually, we can have this option just 'select SPARSEMEM'
config MEMORY_HOTPLUG
bool "Allow for memory hot-add"
diff --git a/mm/filemap.c b/mm/filemap.c
index a0701e6..e32efed8 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -129,6 +129,10 @@ void __delete_from_page_cache(struct page *page)
page->mapping = NULL;
/* Leave page->index set: truncation lookup relies upon it */
mapping->nrpages--;
+ #ifdef CONFIG_LOWMEMORY_READAHEAD
+ page->ioprio = 0;
+ #endif
+
__dec_zone_page_state(page, NR_FILE_PAGES);
if (PageSwapBacked(page))
__dec_zone_page_state(page, NR_SHMEM);
diff --git a/mm/readahead.c b/mm/readahead.c
index cbcbb02..dd07cfe 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -159,6 +159,11 @@ __do_page_cache_readahead(struct address_space
*mapping, struct file *filp,
int page_idx;
int ret = 0;
loff_t isize = i_size_read(inode);
+#ifdef CONFIG_LOWMEMORY_READAHEAD
+ int class = 0;
+ if (p->io_context)
+ class = IOPRIO_PRIO_CLASS(p->io_context->ioprio);
+#endif
if (isize == 0)
goto out;
@@ -177,12 +182,21 @@ __do_page_cache_readahead(struct address_space
*mapping, struct file *filp,
rcu_read_lock();
page = radix_tree_lookup(&mapping->page_tree, page_offset);
rcu_read_unlock();
- if (page)
- continue;
-
+ if (page){
+#ifdef CONFIG_LOWMEMORY_READAHEAD
+ if (class == IOPRIO_CLASS_RT) {
+ page->ioprio = 1;
+#endif
+ continue;
+ }
page = page_cache_alloc_readahead(mapping);
if (!page)
break;
+#ifdef CONFIG_LOWMEMORY_READAHEAD
+ if (class == IOPRIO_CLASS_RT) {
+ page->ioprio = 1;
+#endif
+
page->index = page_offset;
list_add(&page->lru, &page_pool);
if (page_idx == nr_to_read - lookahead_size)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 753a2dc..86e03aa 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -728,8 +728,14 @@ static enum page_references
page_check_references(struct page *page,
}
/* Reclaim if clean, defer dirty pages to writeback */
- if (referenced_page && !PageSwapBacked(page))
- return PAGEREF_RECLAIM_CLEAN;
+ if (referenced_page && !PageSwapBacked(page)) {
+#ifdef CONFIG_LOWMEMORY_READAHEAD
+ if (page->ioprio == 1) {
+ return PAGEREF_ACTIVATE;
+ } else
+#endif
+ return PAGEREF_RECLAIM_CLEAN;
+ }
return PAGEREF_RECLAIM;
}
--
1.7.6
--
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