Commit 3ef5d263 authored by Ojaswin Mujoo's avatar Ojaswin Mujoo Committed by Theodore Ts'o
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ext4: Add counter to track successful allocation of goal length 



Track number of allocations where the length of blocks allocated is equal to the
length of goal blocks (post normalization). This metric could be useful if
making changes to the allocator logic in the future as it could give us
visibility into how often do we trim our requests.

PS: ac_b_ex.fe_len might get modified due to preallocation efforts and
hence we use ac_f_ex.fe_len instead since we want to compare how much the
allocator was able to actually find.

Signed-off-by: default avatarOjaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: default avatarRitesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/343620e2be8a237239ea2613a7a866ee8607e973.1685449706.git.ojaswin@linux.ibm.com


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent fdd9a009

fs/ext4/ext4.h

+1 −0
Original line number Diff line number Diff line
@@ -1558,6 +1558,7 @@ struct ext4_sb_info { 
	atomic_t s_bal_cX_ex_scanned[EXT4_MB_NUM_CRS];	/* total extents scanned */

	atomic_t s_bal_groups_scanned;	/* number of groups scanned */

	atomic_t s_bal_goals;	/* goal hits */

	atomic_t s_bal_len_goals;	/* len goal hits */

	atomic_t s_bal_breaks;	/* too long searches */

	atomic_t s_bal_2orders;	/* 2^order hits */

	atomic_t s_bal_cr0_bad_suggestions;

fs/ext4/mballoc.c

+3 −0
Original line number Diff line number Diff line
@@ -2965,6 +2965,7 @@ int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset) 
		   atomic64_read(&sbi->s_bal_cX_failed[CR3]));

	seq_printf(seq, "\textents_scanned: %u\n", atomic_read(&sbi->s_bal_ex_scanned));

	seq_printf(seq, "\t\tgoal_hits: %u\n", atomic_read(&sbi->s_bal_goals));

	seq_printf(seq, "\t\tlen_goal_hits: %u\n", atomic_read(&sbi->s_bal_len_goals));

	seq_printf(seq, "\t\t2^n_hits: %u\n", atomic_read(&sbi->s_bal_2orders));

	seq_printf(seq, "\t\tbreaks: %u\n", atomic_read(&sbi->s_bal_breaks));

	seq_printf(seq, "\t\tlost: %u\n", atomic_read(&sbi->s_mb_lost_chunks));
@@ -4410,6 +4411,8 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac) 
		if (ac->ac_g_ex.fe_start == ac->ac_b_ex.fe_start &&

				ac->ac_g_ex.fe_group == ac->ac_b_ex.fe_group)

			atomic_inc(&sbi->s_bal_goals);

		if (ac->ac_f_ex.fe_len == ac->ac_g_ex.fe_len)

			atomic_inc(&sbi->s_bal_len_goals);

		if (ac->ac_found > sbi->s_mb_max_to_scan)

			atomic_inc(&sbi->s_bal_breaks);

	}