: Hibernation: lower/better control the amount of pages used for buffering

Hi Rafael,

Hopefully, this one has your comments addressed. Thanks for reviewing!

---------------------------------------
Hibernation/thaw improvements:

1. Set maximum number of pages for read buffering consistently, instead of inadvertently depending on the size of the sector type.

2. Use at most one quarter of free pages for read buffering.

3. Require that number of free pages when writing the image never falls below three quarters of total free pages available.

Signed-off-by Bojan Smojver <[email protected]>

---
 kernel/power/swap.c |   32 +++++++++++++++++++++-----------
 1 files changed, 21 insertions(+), 11 deletions(-)

kernel/power/swap.c +1 -1

index 8742fd0..6c58fa3 100644
@@ -6,7 +6,7 @@
  *
  * Copyright (C) 1998,2001-2005 Pavel Machek <[email protected]>
  * Copyright (C) 2006 Rafael J. Wysocki <[email protected]>
- * Copyright (C) 2010 Bojan Smojver <[email protected]>
+ * Copyright (C) 2010-2012 Bojan Smojver <[email protected]>
  *
  * This file is released under the GPLv2.
  *

kernel/power/swap.c +15 -11

+
 struct swap_map_page {
 	sector_t entries[MAP_PAGE_ENTRIES];
 	sector_t next_swap;

@@ -72,7 +78,7 @@ struct swap_map_handle {
 	sector_t cur_swap;
 	sector_t first_sector;
 	unsigned int k;
-	unsigned long nr_free_pages, written;
+	unsigned long reqd_free_pages;
 	u32 crc32;
 };
 

@@ -316,8 +322,7 @@ static int get_swap_writer(struct swap_map_handle *handle)
 		goto err_rel;
 	}
 	handle->k = 0;
-	handle->nr_free_pages = nr_free_pages() >> 1;
-	handle->written = 0;
+	handle->reqd_free_pages = reqd_free_pages();
 	handle->first_sector = handle->cur_swap;
 	return 0;
 err_rel:

@@ -352,11 +357,15 @@ static int swap_write_page(struct swap_map_handle *handle, void *buf,
 		handle->cur_swap = offset;
 		handle->k = 0;
 	}
-	if (bio_chain && ++handle->written > handle->nr_free_pages) {
+	if (bio_chain && nr_free_pages() < handle->reqd_free_pages) {
 		error = hib_wait_on_bio_chain(bio_chain);
 		if (error)
 			goto out;
-		handle->written = 0;
+		/*
+		 * Recalculate the number of required free pages, to make sure
+		 * we never take more than a quarter.
+		 */
+		handle->reqd_free_pages = reqd_free_pages();
 	}
  out:
 	return error;

@@ -404,7 +413,7 @@ static int swap_writer_finish(struct swap_map_handle *handle,
 #define LZO_THREADS	3
 
 /* Maximum number of pages for read buffering. */
-#define LZO_READ_PAGES	(MAP_PAGE_ENTRIES * 8)
+#define LZO_READ_PAGES	8192
 
 
 /**

@@ -615,10 +624,10 @@ static int save_image_lzo(struct swap_map_handle *handle,
 	}
 
 	/*
-	 * Adjust number of free pages after all allocations have been done.
-	 * We don't want to run out of pages when writing.
+	 * Adjust the number of required free pages after all allocations have
+	 * been done. We don't want to run out of pages when writing.
 	 */
-	handle->nr_free_pages = nr_free_pages() >> 1;
+	handle->reqd_free_pages = reqd_free_pages();
 
 	/*
 	 * Start the CRC32 thread.

@@ -1129,8 +1138,9 @@ static int load_image_lzo(struct swap_map_handle *handle,
 
 	/*
 	 * Adjust number of pages for read buffering, in case we are short.
+	 * Never take more than a quarter of all available pages.
 	 */
-	read_pages = (nr_free_pages() - snapshot_get_image_size()) >> 1;
+	read_pages = (nr_free_pages() - snapshot_get_image_size()) / 4;
 	read_pages = clamp_val(read_pages, LZO_CMP_PAGES, LZO_READ_PAGES);
 
 	for (i = 0; i < read_pages; i++) {
---------------------------------------

If you define a macro, please use capital letters in the name. Also, the parentheses aren't necessary I think.

Perhaps it would be better to use a static inline function instead?

Quoted 3 lines · Rafael J. Wysocki

If you define a macro, please use capital letters in the name. Also, the parentheses aren't necessary I think.

Quoted 1 line

Perhaps it would be better to use a static inline function instead?

Hmm, was just following the nr_free_pages() definition in swap.h:

/* Definition of global_page_state not available yet */ #define nr_free_pages() global_page_state(NR_FREE_PAGES)

Still no good?

Not really, that should be a static inline too. :-)

Quoted 1 line · Rafael J. Wysocki

Not really, that should be a static inline too. :-)

OK, I'll send you a v6 with REQD_FREE_PAGES.

That's better, but what's wrong with a static inline, actually?

Quoted 1 line · Rafael J. Wysocki

That's better, but what's wrong with a static inline, actually?

Nothing, if that is what is required to get the patch accepted. :-)

I just thought that given that nr_free_pages() is already a macro with no side effects, it would make sense for reqd_free_pages() or REQD_FREE_PAGES to remain a macro.

But, if you insist on static inline, I'll do static inline. Let me know.

Please do.

You can even convert nr_free_pages() to a static inline while you're at it. :-)