linux-ext4 - [RFCv1 58/72] e2fsck: make default smallest RA size to 1M

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Date:   Mon,  7 Nov 2022 17:51:46 +0530
From:   "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
To:     Theodore Ts'o <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>,
        Wang Shilong <wshilong@....com>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Li Xi <lixi@....com>, Ritesh Harjani <ritesh.list@...il.com>
Subject: [RFCv1 58/72] e2fsck: make default smallest RA size to 1M

From: Wang Shilong <wshilong@....com>

If we have a smaller inodes per group, default ra size could
be very small(etc 128KiB), this hurts performances.

Tune above 128K to 1M, i see pass1 time drop down from
677.12 seconds to 246 secons with 32 threads.

Signed-off-by: Wang Shilong <wshilong@....com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
---
 e2fsck/readahead.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/e2fsck/readahead.c b/e2fsck/readahead.c
index 38d4ec42..40b73664 100644
--- a/e2fsck/readahead.c
+++ b/e2fsck/readahead.c
@@ -234,6 +234,8 @@ int e2fsck_can_readahead(ext2_filsys fs)
 	return err != EXT2_ET_OP_NOT_SUPPORTED;
 }
 
+#define MIN_DEFAULT_RA	(1024 * 1024)
+
 unsigned long long e2fsck_guess_readahead(ext2_filsys fs)
 {
 	unsigned long long guess;
@@ -245,6 +247,8 @@ unsigned long long e2fsck_guess_readahead(ext2_filsys fs)
 	 * in e2fsck runtime.
 	 */
 	guess = 2ULL * fs->blocksize * fs->inode_blocks_per_group;
+	if (guess < MIN_DEFAULT_RA)
+		guess = MIN_DEFAULT_RA;
 
 	/* Disable RA if it'd use more 1/50th of RAM. */
 	if (get_memory_size() > (guess * 50))
-- 
2.37.3