Re: [PATCH]: Improve performance of LZO hibernation

[Bojan Smojver]

On Mon, 2011-09-19 at 14:29 +1000, Bojan Smojver wrote:
> The want = MAP_PAGE_ENTRIES part is a bug for sure (a leftover from
> the previous version of the patch). The value of want should be set to
> npages, once npages is set after the page allocation loop, of course.

OK, v2 of the patch is here. Should address the above and the cleanup
was also made simpler. In addition, pages required for reading the image
are allocated last, which was supposed to be the case from the start.

-----------------------------------
Use threads for LZO compression/decompression on hibernate/thaw.
Improve read buffering on thaw.
v2

Signed-off-by: Bojan Smojver <bojan@xxxxxxxxxxxxx>
---
 kernel/power/swap.c |  525 +++++++++++++++++++++++++++++++++++++--------------
 1 files changed, 387 insertions(+), 138 deletions(-)

diff --git a/kernel/power/swap.c b/kernel/power/swap.c
index 7c97c3a..6d26338 100644
--- a/kernel/power/swap.c
+++ b/kernel/power/swap.c
@@ -27,6 +27,9 @@
 #include <linux/slab.h>
 #include <linux/lzo.h>
 #include <linux/vmalloc.h>
+#include <linux/cpu.h>
+#include <linux/atomic.h>
+#include <linux/kthread.h>
 
 #include "power.h"
 
@@ -372,6 +375,9 @@ static int swap_writer_finish(struct swap_map_handle *handle,
 			             LZO_HEADER, PAGE_SIZE)
 #define LZO_CMP_SIZE	(LZO_CMP_PAGES * PAGE_SIZE)
 
+/* Maximum number of threads for compression/decompression. */
+#define LZO_THREADS	2
+
 /**
  *	save_image - save the suspend image data
  */
@@ -419,6 +425,46 @@ static int save_image(struct swap_map_handle *handle,
 	return ret;
 }
 
+/**
+ * Structure used for LZO data compression.
+ */
+struct cmp_data {
+	struct task_struct *thr;                  /* thread */
+	atomic_t ready;                           /* ready to start flag */
+	atomic_t stop;                            /* ready to stop flag */
+	wait_queue_head_t go;                     /* start compression */
+	wait_queue_head_t done;                   /* compression done */
+	int ret;                                  /* return code */
+	size_t unc_len;                           /* uncompressed length */
+	size_t cmp_len;                           /* compressed length */
+	unsigned char unc[LZO_UNC_SIZE];          /* uncompressed buffer */
+	unsigned char cmp[LZO_CMP_SIZE];          /* compressed buffer */
+	unsigned char wrk[LZO1X_1_MEM_COMPRESS];  /* compression workspace */
+};
+
+/**
+ * Compression function that runs in its own thread.
+ */
+static int lzo_compress_threadfn(void *data)
+{
+	struct cmp_data *d = data;
+
+	while(1) {
+		wait_event(d->go, atomic_read(&d->ready) ||
+		                  kthread_should_stop());
+		if (kthread_should_stop())
+			break;
+
+		atomic_set(&d->ready, 0);
+		d->ret = lzo1x_1_compress(d->unc, d->unc_len,
+			                  d->cmp + LZO_HEADER, &d->cmp_len,
+		                          d->wrk);
+		atomic_set(&d->stop, 1);
+		wake_up(&d->done);
+	}
+
+	return 0;
+}
 
 /**
  * save_image_lzo - Save the suspend image data compressed with LZO.
@@ -434,41 +480,75 @@ static int save_image_lzo(struct swap_map_handle *handle,
 	int ret = 0;
 	int nr_pages;
 	int err2;
+	int cpu;
 	struct bio *bio;
 	struct timeval start;
 	struct timeval stop;
-	size_t off, unc_len, cmp_len;
-	unsigned char *unc, *cmp, *wrk, *page;
+	size_t off, thr, cthr, nthr;
+	unsigned char *page = NULL;
+	struct cmp_data *data = NULL;
+
+	/* 
+	 * Get more grunt. We don't care if this fails - we'll do it with just
+	 * one core in that case.
+	 */
+	enable_nonboot_cpus();
+
+	/*
+	 * We'll limit the number of threads for compression to limit memory
+	 * footprint.
+	 */
+	nthr = num_online_cpus() - 1;
+	nthr = nthr > LZO_THREADS ? LZO_THREADS : (nthr < 1 ? 1 : nthr);
 
 	page = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
 	if (!page) {
 		printk(KERN_ERR "PM: Failed to allocate LZO page\n");
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto out_clean;
 	}
 
-	wrk = vmalloc(LZO1X_1_MEM_COMPRESS);
-	if (!wrk) {
-		printk(KERN_ERR "PM: Failed to allocate LZO workspace\n");
-		free_page((unsigned long)page);
-		return -ENOMEM;
+	data = vmalloc(sizeof(*data) * nthr);
+	if (!data) {
+		printk(KERN_ERR "PM: Failed to allocate LZO data\n");
+		ret = -ENOMEM;
+		goto out_clean;
 	}
-
-	unc = vmalloc(LZO_UNC_SIZE);
-	if (!unc) {
-		printk(KERN_ERR "PM: Failed to allocate LZO uncompressed\n");
-		vfree(wrk);
-		free_page((unsigned long)page);
-		return -ENOMEM;
+	for (thr = 0; thr < nthr; thr++)
+		memset(&data[thr], 0, offsetof(struct cmp_data, go));
+
+	/*
+	 * Start the compression threads.
+	 */
+	for (thr = 0; thr < nthr; thr++) {
+		init_waitqueue_head(&data[thr].go);
+		init_waitqueue_head(&data[thr].done);
+
+		data[thr].thr = kthread_create(lzo_compress_threadfn,
+		                               &data[thr],
+		                               "image_compress/%zu", thr);
+		if (IS_ERR(data[thr].thr)) {
+			data[thr].thr = NULL;
+			printk(KERN_ERR
+			       "PM: Cannot start compression threads\n");
+			ret = -ENOMEM;
+			goto out_clean;
+		}
 	}
 
-	cmp = vmalloc(LZO_CMP_SIZE);
-	if (!cmp) {
-		printk(KERN_ERR "PM: Failed to allocate LZO compressed\n");
-		vfree(unc);
-		vfree(wrk);
-		free_page((unsigned long)page);
-		return -ENOMEM;
+	/*
+	 * Bind the threads to CPUs and wake them up.
+	 */
+	thr = 0;
+	for_each_online_cpu(cpu) {
+		if (cpu == smp_processor_id())
+			continue;
+		kthread_bind(data[thr++].thr, cpu);
+		if (thr >= nthr)
+			break;
 	}
+	for (thr = 0; thr < nthr; thr++)
+		wake_up_process(data[thr].thr);
 
 	printk(KERN_INFO
 		"PM: Compressing and saving image data (%u pages) ...     ",
@@ -480,54 +560,75 @@ static int save_image_lzo(struct swap_map_handle *handle,
 	bio = NULL;
 	do_gettimeofday(&start);
 	for (;;) {
-		for (off = 0; off < LZO_UNC_SIZE; off += PAGE_SIZE) {
-			ret = snapshot_read_next(snapshot);
-			if (ret < 0)
-				goto out_finish;
-
-			if (!ret)
+		for (thr = 0; thr < nthr; thr++) {
+			for (off = 0; off < LZO_UNC_SIZE; off += PAGE_SIZE) {
+				ret = snapshot_read_next(snapshot);
+				if (ret < 0)
+					goto out_finish;
+
+				if (!ret)
+					break;
+
+				memcpy(data[thr].unc + off,
+				       data_of(*snapshot), PAGE_SIZE);
+
+				if (!(nr_pages % m))
+					printk(KERN_CONT "\b\b\b\b%3d%%",
+				               nr_pages / m);
+				nr_pages++;
+			}
+			if (!off)
 				break;
 
-			memcpy(unc + off, data_of(*snapshot), PAGE_SIZE);
+			data[thr].unc_len = off;
 
-			if (!(nr_pages % m))
-				printk(KERN_CONT "\b\b\b\b%3d%%", nr_pages / m);
-			nr_pages++;
+			atomic_set(&data[thr].ready, 1);
+			wake_up(&data[thr].go);
 		}
 
-		if (!off)
+		if (!thr)
 			break;
 
-		unc_len = off;
-		ret = lzo1x_1_compress(unc, unc_len,
-		                       cmp + LZO_HEADER, &cmp_len, wrk);
-		if (ret < 0) {
-			printk(KERN_ERR "PM: LZO compression failed\n");
-			break;
-		}
+		for (cthr = thr, thr = 0; thr < cthr; thr++) {
+			wait_event(data[thr].done,
+			           atomic_read(&data[thr].stop));
+			atomic_set(&data[thr].stop, 0);
 
-		if (unlikely(!cmp_len ||
-		             cmp_len > lzo1x_worst_compress(unc_len))) {
-			printk(KERN_ERR "PM: Invalid LZO compressed length\n");
-			ret = -1;
-			break;
-		}
-
-		*(size_t *)cmp = cmp_len;
+			ret = data[thr].ret;
 
-		/*
-		 * Given we are writing one page at a time to disk, we copy
-		 * that much from the buffer, although the last bit will likely
-		 * be smaller than full page. This is OK - we saved the length
-		 * of the compressed data, so any garbage at the end will be
-		 * discarded when we read it.
-		 */
-		for (off = 0; off < LZO_HEADER + cmp_len; off += PAGE_SIZE) {
-			memcpy(page, cmp + off, PAGE_SIZE);
+			if (ret < 0) {
+				printk(KERN_ERR "PM: LZO compression failed\n");
+				goto out_finish;
+			}
 
-			ret = swap_write_page(handle, page, &bio);
-			if (ret)
+			if (unlikely(!data[thr].cmp_len ||
+			             data[thr].cmp_len >
+			             lzo1x_worst_compress(data[thr].unc_len))) {
+				printk(KERN_ERR
+				       "PM: Invalid LZO compressed length\n");
+				ret = -1;
 				goto out_finish;
+			}
+
+			*(size_t *)data[thr].cmp = data[thr].cmp_len;
+
+			/*
+			 * Given we are writing one page at a time to disk, we
+			 * copy that much from the buffer, although the last
+			 * bit will likely be smaller than full page. This is
+			 * OK - we saved the length of the compressed data, so
+			 * any garbage at the end will be discarded when we
+			 * read it.
+			 */
+			for (off = 0;
+			     off < LZO_HEADER + data[thr].cmp_len;
+			     off += PAGE_SIZE) {
+				memcpy(page, data[thr].cmp + off, PAGE_SIZE);
+
+				ret = swap_write_page(handle, page, &bio);
+				if (ret)
+					goto out_finish;
+			}
 		}
 	}
 
@@ -541,11 +642,16 @@ out_finish:
 	else
 		printk(KERN_CONT "\n");
 	swsusp_show_speed(&start, &stop, nr_to_write, "Wrote");
-
-	vfree(cmp);
-	vfree(unc);
-	vfree(wrk);
-	free_page((unsigned long)page);
+out_clean:
+	for (thr = 0; thr < nthr; thr++) {
+		if (data[thr].thr) {
+			kthread_stop(data[thr].thr);
+			wake_up(&data[thr].go);
+		}
+	}
+	if (data) vfree(data);
+	if (page) free_page((unsigned long)page);
+	disable_nonboot_cpus();
 
 	return ret;
 }
@@ -743,6 +849,46 @@ static int load_image(struct swap_map_handle *handle,
 }
 
 /**
+ * Structure used for LZO data decompression.
+ */
+struct dec_data {
+	struct task_struct *thr;                  /* thread */
+	atomic_t ready;                           /* ready to start flag */
+	atomic_t stop;                            /* ready to stop flag */
+	wait_queue_head_t go;                     /* start compression */
+	wait_queue_head_t done;                   /* compression done */
+	int ret;                                  /* return code */
+	size_t unc_len;                           /* uncompressed length */
+	size_t cmp_len;                           /* compressed length */
+	unsigned char unc[LZO_UNC_SIZE];          /* uncompressed buffer */
+	unsigned char cmp[LZO_CMP_SIZE];          /* compressed buffer */
+};
+
+/**
+ * Deompression function that runs in its own thread.
+ */
+static int lzo_decompress_threadfn(void *data)
+{
+	struct dec_data *d = data;
+
+	while (1) {
+		wait_event(d->go, atomic_read(&d->ready) ||
+		                  kthread_should_stop());
+		if (kthread_should_stop())
+			break;
+
+		atomic_set(&d->ready, 0);
+		d->unc_len = LZO_UNC_SIZE;
+		d->ret = lzo1x_decompress_safe(d->cmp + LZO_HEADER, d->cmp_len,
+		                               d->unc, &d->unc_len);
+		atomic_set(&d->stop, 1);
+		wake_up(&d->done);
+	}
+
+	return 0;
+}
+
+/**
  * load_image_lzo - Load compressed image data and decompress them with LZO.
  * @handle: Swap map handle to use for loading data.
  * @snapshot: Image to copy uncompressed data into.
@@ -754,45 +900,85 @@ static int load_image_lzo(struct swap_map_handle *handle,
 {
 	unsigned int m;
 	int error = 0;
+	int cpu;
 	struct bio *bio;
 	struct timeval start;
 	struct timeval stop;
 	unsigned nr_pages;
-	size_t i, off, unc_len, cmp_len;
-	unsigned char *unc, *cmp, *page[LZO_CMP_PAGES];
-
-	for (i = 0; i < LZO_CMP_PAGES; i++) {
-		page[i] = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
-		if (!page[i]) {
-			printk(KERN_ERR "PM: Failed to allocate LZO page\n");
-
-			while (i)
-				free_page((unsigned long)page[--i]);
+	size_t i, off, thr, cthr, nthr;
+	size_t ring = 0, pg = 0, npages, have = 0, want, need, asked = 0;
+	unsigned char **page = NULL;
+	struct dec_data *data = NULL;
+
+	/*
+	 * We'll limit the number of threads for decompression to limit memory
+	 * footprint.
+	 */
+	nthr = num_online_cpus() - 1;
+	nthr = nthr > LZO_THREADS ? LZO_THREADS : (nthr < 1 ? 1 : nthr);
+
+	page = vmalloc(sizeof(*page) * MAP_PAGE_ENTRIES);
+	if (!page) {
+		printk(KERN_ERR "PM: Failed to allocate LZO page\n");
+		error = -ENOMEM;
+		goto out_clean;
+	}
+	memset(page, 0, sizeof(*page) * MAP_PAGE_ENTRIES);
 
-			return -ENOMEM;
+	data = vmalloc(sizeof(*data) * nthr);
+	if (!data) {
+		printk(KERN_ERR "PM: Failed to allocate LZO data\n");
+		error = -ENOMEM;
+		goto out_clean;
+	}
+	for (thr = 0; thr < nthr; thr++)
+		memset(&data[thr], 0, offsetof(struct cmp_data, go));
+
+	/*
+	 * Start the decompression threads.
+	 */
+	for (thr = 0; thr < nthr; thr++) {
+		init_waitqueue_head(&data[thr].go);
+		init_waitqueue_head(&data[thr].done);
+
+		data[thr].thr = kthread_create(lzo_decompress_threadfn,
+		                               &data[thr],
+		                               "image_decompress/%zu", thr);
+		if (IS_ERR(data[thr].thr)) {
+			data[thr].thr = NULL;
+			printk(KERN_ERR
+			       "PM: Cannot start decompression threads\n");
+			error = -ENOMEM;
+			goto out_clean;
 		}
 	}
 
-	unc = vmalloc(LZO_UNC_SIZE);
-	if (!unc) {
-		printk(KERN_ERR "PM: Failed to allocate LZO uncompressed\n");
-
-		for (i = 0; i < LZO_CMP_PAGES; i++)
-			free_page((unsigned long)page[i]);
-
-		return -ENOMEM;
+	for (i = 0; i < MAP_PAGE_ENTRIES; i++) {
+		page[i] = (void *)__get_free_page(__GFP_WAIT | __GFP_HIGH);
+		if (!page[i]) {
+			if (i < LZO_CMP_PAGES) {
+				printk(KERN_ERR
+				       "PM: Failed to allocate LZO pages\n");
+				error = -ENOMEM;
+				goto out_clean;
+			}
+		}
 	}
-
-	cmp = vmalloc(LZO_CMP_SIZE);
-	if (!cmp) {
-		printk(KERN_ERR "PM: Failed to allocate LZO compressed\n");
-
-		vfree(unc);
-		for (i = 0; i < LZO_CMP_PAGES; i++)
-			free_page((unsigned long)page[i]);
-
-		return -ENOMEM;
+	want = npages = i;
+
+	/*
+	 * Bind the threads to CPUs and wake them up.
+	 */
+	thr = 0;
+	for_each_online_cpu(cpu) {
+		if (cpu == smp_processor_id())
+			continue;
+		kthread_bind(data[thr++].thr, cpu);
+		if (thr >= nthr)
+			break;
 	}
+	for (thr = 0; thr < nthr; thr++)
+		wake_up_process(data[thr].thr);
 
 	printk(KERN_INFO
 		"PM: Loading and decompressing image data (%u pages) ...     ",
@@ -808,61 +994,117 @@ static int load_image_lzo(struct swap_map_handle *handle,
 	if (error <= 0)
 		goto out_finish;
 
-	for (;;) {
-		error = swap_read_page(handle, page[0], NULL); /* sync */
-		if (error)
-			break;
-
-		cmp_len = *(size_t *)page[0];
-		if (unlikely(!cmp_len ||
-		             cmp_len > lzo1x_worst_compress(LZO_UNC_SIZE))) {
-			printk(KERN_ERR "PM: Invalid LZO compressed length\n");
-			error = -1;
-			break;
+	for(;;) {
+		for (i = 0; have < LZO_CMP_PAGES && i < want; i++) {
+			error = swap_read_page(handle, page[ring], &bio);
+			if (error) {
+				/*
+				 * On real read error, finish. On end of data,
+				 * just exit the read loop.
+				 */
+				if (handle->cur &&
+				    handle->cur->entries[handle->k])
+					goto out_finish;
+				else
+					break;
+			}
+			if (++ring >= npages)
+				ring = 0;
 		}
+		asked += i;
+		want -= i;
+
+		/*
+		 * We are out of data, wait for some more.
+		 */
+		if (!have) {
+			if (!asked)
+				break;
 
-		for (off = PAGE_SIZE, i = 1;
-		     off < LZO_HEADER + cmp_len; off += PAGE_SIZE, i++) {
-			error = swap_read_page(handle, page[i], &bio);
+			error = hib_wait_on_bio_chain(&bio);
 			if (error)
 				goto out_finish;
+			have += asked;
+			asked = 0;
 		}
 
-		error = hib_wait_on_bio_chain(&bio); /* need all data now */
-		if (error)
-			goto out_finish;
+		for (thr = 0; have && thr < nthr; thr++) {
+			data[thr].cmp_len = *(size_t *)page[pg];
+			if (unlikely(!data[thr].cmp_len ||
+			             data[thr].cmp_len >
+			             lzo1x_worst_compress(LZO_UNC_SIZE))) {
+				printk(KERN_ERR
+				       "PM: Invalid LZO compressed length\n");
+				error = -1;
+				goto out_finish;
+			}
 
-		for (off = 0, i = 0;
-		     off < LZO_HEADER + cmp_len; off += PAGE_SIZE, i++) {
-			memcpy(cmp + off, page[i], PAGE_SIZE);
-		}
+			need = DIV_ROUND_UP(data[thr].cmp_len + LZO_HEADER,
+			                    PAGE_SIZE);
+			if (need > have)
+				break;
 
-		unc_len = LZO_UNC_SIZE;
-		error = lzo1x_decompress_safe(cmp + LZO_HEADER, cmp_len,
-		                              unc, &unc_len);
-		if (error < 0) {
-			printk(KERN_ERR "PM: LZO decompression failed\n");
-			break;
+			for (off = 0;
+			     off < LZO_HEADER + data[thr].cmp_len;
+			     off += PAGE_SIZE) {
+				memcpy(data[thr].cmp + off,
+				       page[pg], PAGE_SIZE);
+				have--;
+				want++;
+				if (++pg >= npages)
+					pg = 0;
+			}
+
+			atomic_set(&data[thr].ready, 1);
+			wake_up(&data[thr].go);
 		}
 
-		if (unlikely(!unc_len ||
-		             unc_len > LZO_UNC_SIZE ||
-		             unc_len & (PAGE_SIZE - 1))) {
-			printk(KERN_ERR "PM: Invalid LZO uncompressed length\n");
-			error = -1;
-			break;
+		/*
+		 * Wait for more data while we are decompressing.
+		 */
+		if (have < LZO_CMP_PAGES && asked) {
+			error = hib_wait_on_bio_chain(&bio);
+			if (error)
+				goto out_finish;
+			have += asked;
+			asked = 0;
 		}
 
-		for (off = 0; off < unc_len; off += PAGE_SIZE) {
-			memcpy(data_of(*snapshot), unc + off, PAGE_SIZE);
+		for (cthr = thr, thr = 0; thr < cthr; thr++) {
+			wait_event(data[thr].done,
+			           atomic_read(&data[thr].stop));
+			atomic_set(&data[thr].stop, 0);
 
-			if (!(nr_pages % m))
-				printk("\b\b\b\b%3d%%", nr_pages / m);
-			nr_pages++;
+			error = data[thr].ret;
 
-			error = snapshot_write_next(snapshot);
-			if (error <= 0)
+			if (error < 0) {
+				printk(KERN_ERR
+				       "PM: LZO decompression failed\n");
 				goto out_finish;
+			}
+
+			if (unlikely(!data[thr].unc_len ||
+			             data[thr].unc_len > LZO_UNC_SIZE ||
+			             data[thr].unc_len & (PAGE_SIZE - 1))) {
+				printk(KERN_ERR
+				       "PM: Invalid LZO uncompressed length\n");
+				error = -1;
+				goto out_finish;
+			}
+
+			for (off = 0;
+			     off < data[thr].unc_len; off += PAGE_SIZE) {
+				memcpy(data_of(*snapshot),
+				       data[thr].unc + off, PAGE_SIZE);
+
+				if (!(nr_pages % m))
+					printk("\b\b\b\b%3d%%", nr_pages / m);
+				nr_pages++;
+
+				error = snapshot_write_next(snapshot);
+				if (error <= 0)
+					goto out_finish;
+			}
 		}
 	}
 
@@ -876,11 +1118,18 @@ out_finish:
 	} else
 		printk("\n");
 	swsusp_show_speed(&start, &stop, nr_to_read, "Read");
-
-	vfree(cmp);
-	vfree(unc);
-	for (i = 0; i < LZO_CMP_PAGES; i++)
-		free_page((unsigned long)page[i]);
+out_clean:
+	for (i = 0; i < npages; i++)
+		if (page[i])
+			free_page((unsigned long)page[i]);
+	for (thr = 0; thr < nthr; thr++) {
+		if (data[thr].thr) {
+			kthread_stop(data[thr].thr);
+			wake_up(&data[thr].go);
+		}
+	}
+	if (data) vfree(data);
+	if (page) vfree(page);
 
 	return error;
 }
-----------------------------------
 
-- 
Bojan

--
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