linux-ext4 - [PATCH] libext2fs: readahead for meta

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Date:   Mon, 20 Feb 2017 13:03:45 +0300
From:   Artem Blagodarenko <artem.blagodarenko@...il.com>
To:     linux-ext4@...r.kernel.org
Cc:     adilger.kernel@...ger.ca, alexey.lyashkov@...il.com
Subject: [PATCH] libext2fs: readahead for meta_bg

From: Alexey Lyashkov <alexey.lyashkov@...gate.com>

There are ~37k of random IOs with meta_bg option on 300T target.
Debugfs requires 20 minutes to be started. Enabling readahead for
group blocks metadata save time dramatically. Only 12s to start.

Signed-off-by: Alexey Lyashkov <alexey.lyashkov@...gate.com>
---
 lib/ext2fs/openfs.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
index ba501e6..f158b0a 100644
--- a/lib/ext2fs/openfs.c
+++ b/lib/ext2fs/openfs.c
@@ -399,6 +399,12 @@ errcode_t ext2fs_open2(const char *name, const char *io_options,
 #endif
 		dest += fs->blocksize*first_meta_bg;
 	}
+
+	for (i = first_meta_bg ; i < fs->desc_blocks; i++) {
+		blk = ext2fs_descriptor_block_loc2(fs, group_block, i);
+		io_channel_cache_readahead(fs->io, blk, 1);
+	}
+
 	for (i=first_meta_bg ; i < fs->desc_blocks; i++) {
 		blk = ext2fs_descriptor_block_loc2(fs, group_block, i);
 		retval = io_channel_read_blk64(fs->io, blk, 1, dest);
-- 
1.7.1