linux-kernel - [PATCH] f2fs: reduce stack memory cost by using bitfield in struct f2fs_io

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Message-Id: <20230129083045.7754-1-chao@kernel.org>
Date:   Sun, 29 Jan 2023 16:30:45 +0800
From:   Chao Yu <chao@...nel.org>
To:     jaegeuk@...nel.org
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <chao@...nel.org>
Subject: [PATCH] f2fs: reduce stack memory cost by using bitfield in struct f2fs_io_info

This patch tries to use bitfield in struct f2fs_io_info to improve
memory usage.

struct f2fs_io_info {
...
	int need_lock:8;	/* indicate we need to lock cp_rwsem */
	int version:8;		/* version of the node */
	int submitted:1;	/* indicate IO submission */
	int in_list:1;		/* indicate fio is in io_list */
	int is_por:1;		/* indicate IO is from recovery or not */
	int retry:1;		/* need to reallocate block address */
	int encrypted:1;	/* indicate file is encrypted */
	int post_read:1;	/* require post read */
...
};

After this patch, size of struct f2fs_io_info reduces from 136 to 120.

Signed-off-by: Chao Yu <chao@...nel.org>
---
 fs/f2fs/f2fs.h | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index fa41c0dad308..f2f201e2a6a6 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1212,19 +1212,19 @@ struct f2fs_io_info {
 	struct page *encrypted_page;	/* encrypted page */
 	struct page *compressed_page;	/* compressed page */
 	struct list_head list;		/* serialize IOs */
-	bool submitted;		/* indicate IO submission */
-	int need_lock;		/* indicate we need to lock cp_rwsem */
-	bool in_list;		/* indicate fio is in io_list */
-	bool is_por;		/* indicate IO is from recovery or not */
-	bool retry;		/* need to reallocate block address */
 	int compr_blocks;	/* # of compressed block addresses */
-	bool encrypted;		/* indicate file is encrypted */
-	bool post_read;		/* require post read */
+	int need_lock:8;	/* indicate we need to lock cp_rwsem */
+	int version:8;		/* version of the node */
+	int submitted:1;	/* indicate IO submission */
+	int in_list:1;		/* indicate fio is in io_list */
+	int is_por:1;		/* indicate IO is from recovery or not */
+	int retry:1;		/* need to reallocate block address */
+	int encrypted:1;	/* indicate file is encrypted */
+	int post_read:1;	/* require post read */
 	enum iostat_type io_type;	/* io type */
 	struct writeback_control *io_wbc; /* writeback control */
 	struct bio **bio;		/* bio for ipu */
 	sector_t *last_block;		/* last block number in bio */
-	unsigned char version;		/* version of the node */
 };
 
 struct bio_entry {
-- 
2.36.1