linux-kernel - [PATCH] f2fs: change virtual mapping way for compression pages

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Date:   Tue, 11 Aug 2020 12:37:53 +0900
From:   Daeho Jeong <daeho43@...il.com>
To:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com
Cc:     Daeho Jeong <daehojeong@...gle.com>
Subject: [PATCH] f2fs: change virtual mapping way for compression pages

From: Daeho Jeong <daehojeong@...gle.com>

By profiling f2fs compression works, I've found vmap() callings are
bottlenecks of f2fs decompression path. Changing these with
vm_map_ram(), we can enhance f2fs decompression speed pretty much.

[Verification]
dd if=/dev/zero of=dummy bs=1m count=1000
echo 3 > /proc/sys/vm/drop_caches
dd if=dummy of=/dev/zero bs=512k

- w/o compression -
1048576000 bytes (0.9 G) copied, 1.999384 s, 500 M/s
1048576000 bytes (0.9 G) copied, 2.035988 s, 491 M/s
1048576000 bytes (0.9 G) copied, 2.039457 s, 490 M/s

- before patch -
1048576000 bytes (0.9 G) copied, 9.146217 s, 109 M/s
1048576000 bytes (0.9 G) copied, 9.997542 s, 100 M/s
1048576000 bytes (0.9 G) copied, 10.109727 s, 99 M/s

- after patch -
1048576000 bytes (0.9 G) copied, 2.253441 s, 444 M/s
1048576000 bytes (0.9 G) copied, 2.739764 s, 365 M/s
1048576000 bytes (0.9 G) copied, 2.185649 s, 458 M/s

Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
---
 fs/f2fs/compress.c | 42 ++++++++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 6e7db450006c..46b7e359f313 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -554,6 +554,8 @@ static void f2fs_compress_free_page(struct page *page)
 	mempool_free(page, compress_page_pool);
 }
 
+#define MAX_VMAP_RETRIES	3
+
 static int f2fs_compress_pages(struct compress_ctx *cc)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(cc->inode);
@@ -590,13 +592,23 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
 		}
 	}
 
-	cc->rbuf = vmap(cc->rpages, cc->cluster_size, VM_MAP, PAGE_KERNEL_RO);
+	for (i = 0; i < MAX_VMAP_RETRIES; i++) {
+		cc->rbuf = vm_map_ram(cc->rpages, cc->cluster_size, -1);
+		if (cc->rbuf)
+			break;
+		vm_unmap_aliases();
+	}
 	if (!cc->rbuf) {
 		ret = -ENOMEM;
 		goto out_free_cpages;
 	}
 
-	cc->cbuf = vmap(cc->cpages, cc->nr_cpages, VM_MAP, PAGE_KERNEL);
+	for (i = 0; i < MAX_VMAP_RETRIES; i++) {
+		cc->cbuf = vm_map_ram(cc->cpages, cc->nr_cpages, -1);
+		if (cc->cbuf)
+			break;
+		vm_unmap_aliases();
+	}
 	if (!cc->cbuf) {
 		ret = -ENOMEM;
 		goto out_vunmap_rbuf;
@@ -624,8 +636,8 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
 	memset(&cc->cbuf->cdata[cc->clen], 0,
 	       (nr_cpages * PAGE_SIZE) - (cc->clen + COMPRESS_HEADER_SIZE));
 
-	vunmap(cc->cbuf);
-	vunmap(cc->rbuf);
+	vm_unmap_ram(cc->cbuf, cc->nr_cpages);
+	vm_unmap_ram(cc->rbuf, cc->cluster_size);
 
 	for (i = nr_cpages; i < cc->nr_cpages; i++) {
 		f2fs_compress_free_page(cc->cpages[i]);
@@ -642,9 +654,9 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
 	return 0;
 
 out_vunmap_cbuf:
-	vunmap(cc->cbuf);
+	vm_unmap_ram(cc->cbuf, cc->nr_cpages);
 out_vunmap_rbuf:
-	vunmap(cc->rbuf);
+	vm_unmap_ram(cc->rbuf, cc->cluster_size);
 out_free_cpages:
 	for (i = 0; i < cc->nr_cpages; i++) {
 		if (cc->cpages[i])
@@ -715,13 +727,23 @@ void f2fs_decompress_pages(struct bio *bio, struct page *page, bool verity)
 			goto out_free_dic;
 	}
 
-	dic->rbuf = vmap(dic->tpages, dic->cluster_size, VM_MAP, PAGE_KERNEL);
+	for (i = 0; i < MAX_VMAP_RETRIES; i++) {
+		dic->rbuf = vm_map_ram(dic->tpages, dic->cluster_size, -1);
+		if (dic->rbuf)
+			break;
+		vm_unmap_aliases();
+	}
 	if (!dic->rbuf) {
 		ret = -ENOMEM;
 		goto destroy_decompress_ctx;
 	}
 
-	dic->cbuf = vmap(dic->cpages, dic->nr_cpages, VM_MAP, PAGE_KERNEL_RO);
+	for (i = 0; i < MAX_VMAP_RETRIES; i++) {
+		dic->cbuf = vm_map_ram(dic->cpages, dic->nr_cpages, -1);
+		if (dic->cbuf)
+			break;
+		vm_unmap_aliases();
+	}
 	if (!dic->cbuf) {
 		ret = -ENOMEM;
 		goto out_vunmap_rbuf;
@@ -738,9 +760,9 @@ void f2fs_decompress_pages(struct bio *bio, struct page *page, bool verity)
 	ret = cops->decompress_pages(dic);
 
 out_vunmap_cbuf:
-	vunmap(dic->cbuf);
+	vm_unmap_ram(dic->cbuf, dic->nr_cpages);
 out_vunmap_rbuf:
-	vunmap(dic->rbuf);
+	vm_unmap_ram(dic->rbuf, dic->cluster_size);
 destroy_decompress_ctx:
 	if (cops->destroy_decompress_ctx)
 		cops->destroy_decompress_ctx(dic);
-- 
2.28.0.236.gb10cc79966-goog