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Message-ID: <CAKYAXd9trE9b8LYuJLQ3sYn-3b-56MArTMaG0sMS01TPd+cfvA@mail.gmail.com>
Date: Fri, 2 Dec 2011 17:12:36 +0900
From: Namjae Jeon <linkinjeon@...il.com>
To: Kyungmin Park <kmpark@...radead.org>
Cc: tytso@....edu, tm@....ma, lczerner@...hat.com,
linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ext4: auto batched discard support at kernel thread
2011/12/2 Kyungmin Park <kmpark@...radead.org>:
> Hi,
>
> It's proof of concept to run kernel thread for batched discard.
>
> Now it can run fitrim at user level. but it's not clear which deamon run this activity.
> In case of android platform, the launcher is candidate
> but user can change the default launcher then it can't use the fitrim any more.
>
> To address this issue. no dependency with platform. run the fitrim at kernel.
> Basically don't bother the user it runs at 2 clock. Please note that if it's clean state, it doesn't take much time.
>
> Please give opinions and comments.
I think that it is good approach. If we can adjust wake up time and
cycle, it is more better.
And we can avoid performance degradation by copy merging in mmc/sdd internal.
On the other hand lifetime of ssd/mmc is decreased by this patch ?
> Thank you,
> Kyungmin Park
> ---
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 5b0e26a..2cad9b3 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -942,6 +942,7 @@ struct ext4_inode_info {
>
> #define EXT4_MOUNT2_EXPLICIT_DELALLOC 0x00000001 /* User explicitly
> specified delalloc */
> +#define EXT4_MOUNT2_AUTO_DISCARD 0x00000002 /* Auto batched discard */
>
> #define clear_opt(sb, opt) EXT4_SB(sb)->s_mount_opt &= \
> ~EXT4_MOUNT_##opt
> @@ -1249,6 +1250,10 @@ struct ext4_sb_info {
>
> /* record the last minlen when FITRIM is called. */
> atomic_t s_last_trim_minblks;
> +
> + /* timer for periodic auto batched discard */
> + struct timer_list s_auto_discard;
> + struct task_struct *s_auto_discard_thread;
> };
>
> static inline struct ext4_sb_info *EXT4_SB(struct super_block *sb)
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 3858767..a2e9920 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -818,6 +818,10 @@ static void ext4_put_super(struct super_block *sb)
> ext4_abort(sb, "Couldn't clean up the journal");
> }
>
> + if (test_opt2(sb, AUTO_DISCARD)) {
> + kthread_stop(sbi->s_auto_discard_thread);
> + del_timer(&sbi->s_auto_discard);
> + }
> del_timer(&sbi->s_err_report);
> ext4_release_system_zone(sb);
> ext4_mb_release(sb);
> @@ -1144,6 +1148,9 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
> if (test_opt(sb, DISCARD) && !(def_mount_opts & EXT4_DEFM_DISCARD))
> seq_puts(seq, ",discard");
>
> + if (test_opt2(sb, AUTO_DISCARD))
> + seq_puts(seq, ",auto_batched_discard");
> +
> if (test_opt(sb, NOLOAD))
> seq_puts(seq, ",norecovery");
>
> @@ -1333,7 +1340,7 @@ enum {
> Opt_nomblk_io_submit, Opt_block_validity, Opt_noblock_validity,
> Opt_inode_readahead_blks, Opt_journal_ioprio,
> Opt_dioread_nolock, Opt_dioread_lock,
> - Opt_discard, Opt_nodiscard,
> + Opt_discard, Opt_nodiscard, Opt_auto_discard,
> Opt_init_inode_table, Opt_noinit_inode_table,
> };
>
> @@ -1407,6 +1414,7 @@ static const match_table_t tokens = {
> {Opt_dioread_lock, "dioread_lock"},
> {Opt_discard, "discard"},
> {Opt_nodiscard, "nodiscard"},
> + {Opt_auto_discard, "auto_batched_discard"},
> {Opt_init_inode_table, "init_itable=%u"},
> {Opt_init_inode_table, "init_itable"},
> {Opt_noinit_inode_table, "noinit_itable"},
> @@ -1886,6 +1894,9 @@ set_qf_format:
> case Opt_nodiscard:
> clear_opt(sb, DISCARD);
> break;
> + case Opt_auto_discard:
> + set_opt2(sb, AUTO_DISCARD);
> + break;
> case Opt_dioread_nolock:
> set_opt(sb, DIOREAD_NOLOCK);
> break;
> @@ -2763,6 +2774,71 @@ static void print_daily_error_info(unsigned long arg)
> mod_timer(&sbi->s_err_report, jiffies + 24*60*60*HZ); /* Once a day */
> }
>
> +/*
> + * This function is called once a day to make a trim the device
> + */
> +static int ext4_auto_batched_discard_thread(void *data)
> +{
> + struct super_block *sb = data;
> + struct ext4_sb_info *sbi = EXT4_SB(sb);
> + struct fstrim_range range;
> + struct timeval now;
> + struct tm tm;
> + long next;
> + int ret;
> +
> + set_freezable();
> +
> + for (;;) {
> + if (kthread_should_stop())
> + break;
> +
> + if (try_to_freeze())
> + continue;
> +
> + range.start = 0;
> + range.len = ~(__u64)0;
> + range.minlen = SZ_1M;
> +
> + ret = ext4_trim_fs(sb, &range);
> + if (ret < 0)
> + ext4_msg(sb, KERN_NOTICE, "error count: %u", ret);
> + else
> + ext4_msg(sb, KERN_NOTICE, "trimmed size %llu",
> + range.len);
> +
> + do_gettimeofday(&now);
> + time_to_tm((time_t) now.tv_sec, 0, &tm);
> +
> + /* Run the every day at 2 clock */
> + /* XXX need to consider the timezone? */
> + next = 2 - tm.tm_hour;
> + if (next <= 0)
> + next += 24;
> + next *= 60*60*HZ;
> +
> + /* Re-arm the timer for next trim */
> + mod_timer(&sbi->s_auto_discard, jiffies + next);
> +
> + set_current_state(TASK_INTERRUPTIBLE);
> + schedule();
> + }
> +
> + return 0;
> +}
> +
> +static void ext4_auto_batched_discard(unsigned long arg)
> +{
> + struct super_block *sb = (struct super_block *) arg;
> + struct ext4_sb_info *sbi = EXT4_SB(sb);
> +
> + /*
> + * The ext4_trim_fs can't run at timer context
> + * So use the created kthread.
> + */
> + wake_up_process(sbi->s_auto_discard_thread);
> +}
> +
> /* Find next suitable group and run ext4_init_inode_table */
> static int ext4_run_li_request(struct ext4_li_request *elr)
> {
> @@ -3576,6 +3652,21 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> sbi->s_err_report.function = print_daily_error_info;
> sbi->s_err_report.data = (unsigned long) sb;
>
> + if (test_opt2(sb, AUTO_DISCARD)) {
> + init_timer(&sbi->s_auto_discard);
> + sbi->s_auto_discard.function = ext4_auto_batched_discard;
> + sbi->s_auto_discard.data = (unsigned long) sb;
> + sbi->s_auto_discard_thread =
> + kthread_create(ext4_auto_batched_discard_thread, sb,
> + "ext4-batched-discard");
> + if (IS_ERR(sbi->s_auto_discard_thread)) {
> + err = PTR_ERR(sbi->s_auto_discard_thread);
> + goto failed_mount2;
> + }
> + /* One hour is enough to know the time */
> + mod_timer(&sbi->s_auto_discard, jiffies + 1*60*60*HZ);
> + }
> +
> err = percpu_counter_init(&sbi->s_freeclusters_counter,
> ext4_count_free_clusters(sb));
> if (!err) {
> @@ -3848,6 +3939,10 @@ failed_mount_wq:
> sbi->s_journal = NULL;
> }
> failed_mount3:
> + if (test_opt2(sb, AUTO_DISCARD)) {
> + kthread_stop(sbi->s_auto_discard_thread);
> + del_timer(&sbi->s_auto_discard);
> + }
> del_timer(&sbi->s_err_report);
> if (sbi->s_flex_groups)
> ext4_kvfree(sbi->s_flex_groups);
> @@ -4546,6 +4641,22 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
> if (sbi->s_journal == NULL)
> ext4_commit_super(sb, 1);
>
> + if (test_opt2(sb, AUTO_DISCARD) && !sbi->s_auto_discard_thread) {
> + init_timer(&sbi->s_auto_discard);
> + sbi->s_auto_discard.function = ext4_auto_batched_discard;
> + sbi->s_auto_discard.data = (unsigned long) sb;
> + sbi->s_auto_discard_thread =
> + kthread_create(ext4_auto_batched_discard_thread, sb,
> + "ext4-batched-discard");
> + if (IS_ERR(sbi->s_auto_discard_thread)) {
> + err = PTR_ERR(sbi->s_auto_discard_thread);
> + goto restore_opts;
> + }
> +
> + /* One hour is enough to know the time */
> + mod_timer(&sbi->s_auto_discard, jiffies + 1*60*60*HZ);
> + }
> +
> #ifdef CONFIG_QUOTA
> /* Release old quota file names */
> for (i = 0; i < MAXQUOTAS; i++)
> --
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