[PATCH v11]: Hibernation: fix the number of pages used forhibernate/thaw buffering
From: Bojan Smojver
Date: Thu Apr 12 2012 - 17:59:30 EST
Hi Rafael,
Yes, I know - it is getting a bit ridiculous. Such a simple problem, so
many patches. Anyhow...
Here we also fix the calculation of pages for read buffering. Not really
very significant, but may become important in some really tight memory
scenarios. And after thinking more about low_free_pages() inline
function, Per was right - it is better to call an already existing
function, rather than roll our own. Keeps kernel smaller and there is no
significant performance gain otherwise.
Per,
Feel free to reply with your signed-off.
---------------------------------------
Hibernation/thaw fixes/improvements:
1. Calculate the number of required free pages based on non-high memory
pages only, because that is where the buffers will come from.
2. Do not allocate memory for buffers from emergency pools, unless
absolutely required. Do not warn about and do not retry non-essential
failed allocations.
3. Do not check the amount of free pages left on every single page
write, but wait until one map is completely populated and then check.
4. Set maximum number of pages for read buffering consistently, instead
of inadvertently depending on the size of the sector type.
5. Fix copyright line, which I missed when I submitted the hibernation
threading patch.
6. Dispense with bit shifting arithmetic to improve readability.
Signed-off-by: Bojan Smojver <bojan@xxxxxxxxxxxxx>
---
kernel/power/swap.c | 84 +++++++++++++++++++++++++++++++++++----------------
1 files changed, 58 insertions(+), 26 deletions(-)
diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index 8742fd0..11e22c0 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -6,7 +6,7 @@
*
* Copyright (C) 1998,2001-2005 Pavel Machek <pavel@xxxxxx>
* Copyright (C) 2006 Rafael J. Wysocki <rjw@xxxxxxx>
- * Copyright (C) 2010 Bojan Smojver <bojan@xxxxxxxxxxxxx>
+ * Copyright (C) 2010-2012 Bojan Smojver <bojan@xxxxxxxxxxxxx>
*
* This file is released under the GPLv2.
*
@@ -51,6 +51,23 @@
#define MAP_PAGE_ENTRIES (PAGE_SIZE / sizeof(sector_t) - 1)
+/*
+ * Number of free pages that are not high.
+ */
+static inline unsigned long low_free_pages(void)
+{
+ return nr_free_pages() - nr_free_highpages();
+}
+
+/*
+ * Number of pages required to be kept free while writing the image. Always
+ * half of all available low pages before the writing starts.
+ */
+static inline unsigned long reqd_free_pages(void)
+{
+ return low_free_pages() / 2;
+}
+
struct swap_map_page {
sector_t entries[MAP_PAGE_ENTRIES];
sector_t next_swap;
@@ -72,7 +89,7 @@ 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;
};
@@ -265,14 +282,17 @@ static int write_page(void *buf, sector_t offset, struct bio **bio_chain)
return -ENOSPC;
if (bio_chain) {
- src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
+ src = (void *)__get_free_page(__GFP_WAIT | __GFP_NOWARN |
+ __GFP_NORETRY);
if (src) {
copy_page(src, buf);
} else {
ret = hib_wait_on_bio_chain(bio_chain); /* Free pages */
if (ret)
return ret;
- src = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
+ src = (void *)__get_free_page(__GFP_WAIT |
+ __GFP_NOWARN |
+ __GFP_NORETRY);
if (src) {
copy_page(src, buf);
} else {
@@ -316,8 +336,7 @@ 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:
@@ -351,12 +370,17 @@ static int swap_write_page(struct swap_map_handle *handle, void *buf,
clear_page(handle->cur);
handle->cur_swap = offset;
handle->k = 0;
- }
- if (bio_chain && ++handle->written > handle->nr_free_pages) {
- error = hib_wait_on_bio_chain(bio_chain);
- if (error)
- goto out;
- handle->written = 0;
+
+ if (bio_chain && low_free_pages() <= handle->reqd_free_pages) {
+ error = hib_wait_on_bio_chain(bio_chain);
+ if (error)
+ goto out;
+ /*
+ * Recalculate the number of required free pages, to
+ * make sure we never take more than half.
+ */
+ handle->reqd_free_pages = reqd_free_pages();
+ }
}
out:
return error;
@@ -403,8 +427,9 @@ static int swap_writer_finish(struct swap_map_handle *handle,
/* Maximum number of threads for compression/decompression. */
#define LZO_THREADS 3
-/* Maximum number of pages for read buffering. */
-#define LZO_READ_PAGES (MAP_PAGE_ENTRIES * 8)
+/* Minimum/maximum number of pages for read buffering. */
+#define LZO_MIN_RD_PAGES 1024
+#define LZO_MAX_RD_PAGES 8192
/**
@@ -615,12 +640,6 @@ 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.
- */
- handle->nr_free_pages = nr_free_pages() >> 1;
-
- /*
* Start the CRC32 thread.
*/
init_waitqueue_head(&crc->go);
@@ -641,6 +660,12 @@ static int save_image_lzo(struct swap_map_handle *handle,
goto out_clean;
}
+ /*
+ * 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->reqd_free_pages = reqd_free_pages();
+
printk(KERN_INFO
"PM: Using %u thread(s) for compression.\n"
"PM: Compressing and saving image data (%u pages) ... ",
@@ -1051,7 +1076,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
unsigned i, thr, run_threads, nr_threads;
unsigned ring = 0, pg = 0, ring_size = 0,
have = 0, want, need, asked = 0;
- unsigned long read_pages;
+ unsigned long read_pages = 0;
unsigned char **page = NULL;
struct dec_data *data = NULL;
struct crc_data *crc = NULL;
@@ -1063,7 +1088,7 @@ static int load_image_lzo(struct swap_map_handle *handle,
nr_threads = num_online_cpus() - 1;
nr_threads = clamp_val(nr_threads, 1, LZO_THREADS);
- page = vmalloc(sizeof(*page) * LZO_READ_PAGES);
+ page = vmalloc(sizeof(*page) * LZO_MAX_RD_PAGES);
if (!page) {
printk(KERN_ERR "PM: Failed to allocate LZO page\n");
ret = -ENOMEM;
@@ -1128,15 +1153,22 @@ static int load_image_lzo(struct swap_map_handle *handle,
}
/*
- * Adjust number of pages for read buffering, in case we are short.
+ * Set the number of pages for read buffering.
+ * This is complete guesswork, because we'll only know the real
+ * picture once prepare_image() is called, which is much later on
+ * during the image load phase. We'll assume the worst case and
+ * say that none of the image pages are from high memory.
*/
- read_pages = (nr_free_pages() - snapshot_get_image_size()) >> 1;
- read_pages = clamp_val(read_pages, LZO_CMP_PAGES, LZO_READ_PAGES);
+ if (low_free_pages() > snapshot_get_image_size())
+ read_pages = (low_free_pages() - snapshot_get_image_size()) / 2;
+ read_pages = clamp_val(read_pages, LZO_MIN_RD_PAGES, LZO_MAX_RD_PAGES);
for (i = 0; i < read_pages; i++) {
page[i] = (void *)__get_free_page(i < LZO_CMP_PAGES ?
__GFP_WAIT | __GFP_HIGH :
- __GFP_WAIT);
+ __GFP_WAIT | __GFP_NOWARN |
+ __GFP_NORETRY);
+
if (!page[i]) {
if (i < LZO_CMP_PAGES) {
ring_size = i;
---------------------------------------
--
Bojan
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