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Date: Sat, 2 May 2009 09:30:11 -0700
From: Curt Wohlgemuth <curtw@...gle.com>
To: "Theodore Ts'o" <tytso@....edu>
Cc: Michael Rubin <mrubin@...gle.com>,
Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: Make the length of the mb_history file tunable
Hi Ted:
Thanks for sending this out. It was on my list to re-vamp the patch
to use your suggestion of a mount option, but I didn't get a chance.
I tested it on our 2.6.26+patches kernel, and it works fine.
Curt
On Fri, May 1, 2009 at 5:31 PM, Theodore Ts'o <tytso@....edu> wrote:
> From: Curt Wohlgemuth <curtw@...gle.com>
>
> In memory-constrained systems with many partitions, the ~68K for each
> partition for the mb_history buffer can be excessive.
>
> This patch adds a new mount option, mb_history_length, as well as a
> way of setting the default via a module parameter (or via a sysfs
> parameter in /sys/module/ext4/parameter/default_mb_history_length).
> If the mb_history_length is set to zero, the mb_history facility is
> disabled entirely.
>
> Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>
> I completely revamped how how tunable is set. The combination of a
> mount option plus a default which can be tuned via a sysfs file or a
> module parameter is cleaner, and certainly requires less code. (No need
> to open-code new file in /proc, which should be avoided if at all
> possible.)
>
> Anyway, this is what I've dropped into the ext4 patch queue.
>
> fs/ext4/mballoc.c | 13 +++++++------
> fs/ext4/super.c | 18 +++++++++++++++++-
> 2 files changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index dbd47ea..df75855 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2413,7 +2413,8 @@ static void ext4_mb_history_release(struct super_block *sb)
>
> if (sbi->s_proc != NULL) {
> remove_proc_entry("mb_groups", sbi->s_proc);
> - remove_proc_entry("mb_history", sbi->s_proc);
> + if (sbi->s_mb_history_max)
> + remove_proc_entry("mb_history", sbi->s_proc);
> }
> kfree(sbi->s_mb_history);
> }
> @@ -2424,17 +2425,17 @@ static void ext4_mb_history_init(struct super_block *sb)
> int i;
>
> if (sbi->s_proc != NULL) {
> - proc_create_data("mb_history", S_IRUGO, sbi->s_proc,
> - &ext4_mb_seq_history_fops, sb);
> + if (sbi->s_mb_history_max)
> + proc_create_data("mb_history", S_IRUGO, sbi->s_proc,
> + &ext4_mb_seq_history_fops, sb);
> proc_create_data("mb_groups", S_IRUGO, sbi->s_proc,
> &ext4_mb_seq_groups_fops, sb);
> }
>
> - sbi->s_mb_history_max = 1000;
> sbi->s_mb_history_cur = 0;
> spin_lock_init(&sbi->s_mb_history_lock);
> i = sbi->s_mb_history_max * sizeof(struct ext4_mb_history);
> - sbi->s_mb_history = kzalloc(i, GFP_KERNEL);
> + sbi->s_mb_history = i ? kzalloc(i, GFP_KERNEL) : NULL;
> /* if we can't allocate history, then we simple won't use it */
> }
>
> @@ -2444,7 +2445,7 @@ ext4_mb_store_history(struct ext4_allocation_context *ac)
> struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
> struct ext4_mb_history h;
>
> - if (unlikely(sbi->s_mb_history == NULL))
> + if (sbi->s_mb_history == NULL)
> return;
>
> if (!(ac->ac_op & sbi->s_mb_history_filter))
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 7903f20..39223a5 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -47,6 +47,13 @@
> #include "xattr.h"
> #include "acl.h"
>
> +static int default_mb_history_length = 1000;
> +
> +module_param_named(default_mb_history_length, default_mb_history_length,
> + int, 0644);
> +MODULE_PARM_DESC(default_mb_history_length,
> + "Default number of entries saved for mb_history");
> +
> struct proc_dir_entry *ext4_proc_root;
> static struct kset *ext4_kset;
>
> @@ -1042,7 +1049,7 @@ enum {
> Opt_journal_update, Opt_journal_dev,
> Opt_journal_checksum, Opt_journal_async_commit,
> Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
> - Opt_data_err_abort, Opt_data_err_ignore,
> + Opt_data_err_abort, Opt_data_err_ignore, Opt_mb_history_length,
> Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
> Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
> Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err, Opt_resize,
> @@ -1088,6 +1095,7 @@ static const match_table_t tokens = {
> {Opt_data_writeback, "data=writeback"},
> {Opt_data_err_abort, "data_err=abort"},
> {Opt_data_err_ignore, "data_err=ignore"},
> + {Opt_mb_history_length, "mb_history_length=%u"},
> {Opt_offusrjquota, "usrjquota="},
> {Opt_usrjquota, "usrjquota=%s"},
> {Opt_offgrpjquota, "grpjquota="},
> @@ -1329,6 +1337,13 @@ static int parse_options(char *options, struct super_block *sb,
> case Opt_data_err_ignore:
> clear_opt(sbi->s_mount_opt, DATA_ERR_ABORT);
> break;
> + case Opt_mb_history_length:
> + if (match_int(&args[0], &option))
> + return 0;
> + if (option < 0)
> + return 0;
> + sbi->s_mb_history_max = option;
> + break;
> #ifdef CONFIG_QUOTA
> case Opt_usrjquota:
> qtype = USRQUOTA;
> @@ -2345,6 +2360,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
> sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
> sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;
> + sbi->s_mb_history_max = default_mb_history_length;
>
> set_opt(sbi->s_mount_opt, BARRIER);
>
> --
> 1.6.0.4
>
>
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