On Fri 01-09-23 17:28:20, Fengnan Chang wrote:
> In commit a015434480dc("ext4: send parallel discards on commit
> completions"), issue all discard commands in parallel make all
> bios could merged into one request, so lowlevel drive can issue
> multi segments in one time which is more efficiency, but commit
> 55cdd0af2bc5 ("ext4: get discard out of jbd2 commit kthread contex")
> seems broke this way, let's fix it.
>
> In my test:
> 1. create 10 normal files, each file size is 10G.
> 2. deallocate file, punch a 16k holes every 32k.
> 3. trim all fs.
> the time of fstrim fs reduce from 6.7s to 1.3s.
>
> Signed-off-by: Fengnan Chang <[email protected]>
This seems to have fallen through the cracks... I'm sorry for that.
> static int ext4_try_to_trim_range(struct super_block *sb,
> struct ext4_buddy *e4b, ext4_grpblk_t start,
> ext4_grpblk_t max, ext4_grpblk_t minblocks)
> __acquires(ext4_group_lock_ptr(sb, e4b->bd_group))
> __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> {
> - ext4_grpblk_t next, count, free_count;
> + ext4_grpblk_t next, count, free_count, bak;
> void *bitmap;
> + struct ext4_free_data *entry = NULL, *fd, *nfd;
> + struct list_head discard_data_list;
> + struct bio *discard_bio = NULL;
> + struct blk_plug plug;
> + ext4_group_t group = e4b->bd_group;
> + struct ext4_free_extent ex;
> + bool noalloc = false;
> + int ret = 0;
> +
> + INIT_LIST_HEAD(&discard_data_list);
>
> bitmap = e4b->bd_bitmap;
> start = max(e4b->bd_info->bb_first_free, start);
> count = 0;
> free_count = 0;
>
> + blk_start_plug(&plug);
> while (start <= max) {
> start = mb_find_next_zero_bit(bitmap, max + 1, start);
> if (start > max)
> break;
> + bak = start;
> next = mb_find_next_bit(bitmap, max + 1, start);
> -
> if ((next - start) >= minblocks) {
> - int ret = ext4_trim_extent(sb, start, next - start, e4b);
> + /* when only one segment, there is no need to alloc entry */
> + noalloc = (free_count == 0) && (next >= max);
Is the single extent case really worth the complications to save one
allocation? I don't think it is but maybe I'm missing something. Otherwise
the patch looks good to me!
Honza
>
> - if (ret && ret != -EOPNOTSUPP)
> + trace_ext4_trim_extent(sb, group, start, next - start);
> + ex.fe_start = start;
> + ex.fe_group = group;
> + ex.fe_len = next - start;
> + /*
> + * Mark blocks used, so no one can reuse them while
> + * being trimmed.
> + */
> + mb_mark_used(e4b, &ex);
> + ext4_unlock_group(sb, group);
> + ret = ext4_issue_discard(sb, group, start, next - start, &discard_bio);
> + if (!noalloc) {
> + entry = kmem_cache_alloc(ext4_free_data_cachep,
> + GFP_NOFS|__GFP_NOFAIL);
> + entry->efd_start_cluster = start;
> + entry->efd_count = next - start;
> + list_add_tail(&entry->efd_list, &discard_data_list);
> + }
> + ext4_lock_group(sb, group);
> + if (ret < 0)
> break;
> count += next - start;
> }
> @@ -6959,6 +6950,22 @@ __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> break;
> }
>
> + if (discard_bio) {
> + ext4_unlock_group(sb, e4b->bd_group);
> + submit_bio_wait(discard_bio);
> + bio_put(discard_bio);
> + ext4_lock_group(sb, e4b->bd_group);
> + }
> + blk_finish_plug(&plug);
> +
> + if (noalloc && free_count)
> + mb_free_blocks(NULL, e4b, bak, free_count);
> +
> + list_for_each_entry_safe(fd, nfd, &discard_data_list, efd_list) {
> + mb_free_blocks(NULL, e4b, fd->efd_start_cluster, fd->efd_count);
> + kmem_cache_free(ext4_free_data_cachep, fd);
> + }
> +
> return count;
> }
>
> --
> 2.20.1
>
--
Jan Kara <[email protected]>
SUSE Labs, CR
Jan Kara <[email protected]> 于2024年1月9日周二 01:15写道：
>
> On Fri 01-09-23 17:28:20, Fengnan Chang wrote:
> > In commit a015434480dc("ext4: send parallel discards on commit
> > completions"), issue all discard commands in parallel make all
> > bios could merged into one request, so lowlevel drive can issue
> > multi segments in one time which is more efficiency, but commit
> > 55cdd0af2bc5 ("ext4: get discard out of jbd2 commit kthread contex")
> > seems broke this way, let's fix it.
> >
> > In my test:
> > 1. create 10 normal files, each file size is 10G.
> > 2. deallocate file, punch a 16k holes every 32k.
> > 3. trim all fs.
> > the time of fstrim fs reduce from 6.7s to 1.3s.
> >
> > Signed-off-by: Fengnan Chang <[email protected]>
>
> This seems to have fallen through the cracks... I'm sorry for that.
>
> > static int ext4_try_to_trim_range(struct super_block *sb,
> > struct ext4_buddy *e4b, ext4_grpblk_t start,
> > ext4_grpblk_t max, ext4_grpblk_t minblocks)
> > __acquires(ext4_group_lock_ptr(sb, e4b->bd_group))
> > __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> > {
> > - ext4_grpblk_t next, count, free_count;
> > + ext4_grpblk_t next, count, free_count, bak;
> > void *bitmap;
> > + struct ext4_free_data *entry = NULL, *fd, *nfd;
> > + struct list_head discard_data_list;
> > + struct bio *discard_bio = NULL;
> > + struct blk_plug plug;
> > + ext4_group_t group = e4b->bd_group;
> > + struct ext4_free_extent ex;
> > + bool noalloc = false;
> > + int ret = 0;
> > +
> > + INIT_LIST_HEAD(&discard_data_list);
> >
> > bitmap = e4b->bd_bitmap;
> > start = max(e4b->bd_info->bb_first_free, start);
> > count = 0;
> > free_count = 0;
> >
> > + blk_start_plug(&plug);
> > while (start <= max) {
> > start = mb_find_next_zero_bit(bitmap, max + 1, start);
> > if (start > max)
> > break;
> > + bak = start;
> > next = mb_find_next_bit(bitmap, max + 1, start);
> > -
> > if ((next - start) >= minblocks) {
> > - int ret = ext4_trim_extent(sb, start, next - start, e4b);
> > + /* when only one segment, there is no need to alloc entry */
> > + noalloc = (free_count == 0) && (next >= max);
>
> Is the single extent case really worth the complications to save one
> allocation? I don't think it is but maybe I'm missing something. Otherwise
> the patch looks good to me!
yeah, it's necessary, if there is only one segment, alloc memory may cause
performance regression.
Refer to this https://lore.kernel.org/linux-ext4/CALWNXx-6y0=ZDBMicv2qng9pKHWcpJbCvUm9TaRBwg81WzWkWQ@mail.gmail.com/
Thanks.
>
> Honza
>
> >
> > - if (ret && ret != -EOPNOTSUPP)
> > + trace_ext4_trim_extent(sb, group, start, next - start);
> > + ex.fe_start = start;
> > + ex.fe_group = group;
> > + ex.fe_len = next - start;
> > + /*
> > + * Mark blocks used, so no one can reuse them while
> > + * being trimmed.
> > + */
> > + mb_mark_used(e4b, &ex);
> > + ext4_unlock_group(sb, group);
> > + ret = ext4_issue_discard(sb, group, start, next - start, &discard_bio);
> > + if (!noalloc) {
> > + entry = kmem_cache_alloc(ext4_free_data_cachep,
> > + GFP_NOFS|__GFP_NOFAIL);
> > + entry->efd_start_cluster = start;
> > + entry->efd_count = next - start;
> > + list_add_tail(&entry->efd_list, &discard_data_list);
> > + }
> > + ext4_lock_group(sb, group);
> > + if (ret < 0)
> > break;
> > count += next - start;
> > }
> > @@ -6959,6 +6950,22 @@ __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> > break;
> > }
> >
> > + if (discard_bio) {
> > + ext4_unlock_group(sb, e4b->bd_group);
> > + submit_bio_wait(discard_bio);
> > + bio_put(discard_bio);
> > + ext4_lock_group(sb, e4b->bd_group);
> > + }
> > + blk_finish_plug(&plug);
> > +
> > + if (noalloc && free_count)
> > + mb_free_blocks(NULL, e4b, bak, free_count);
> > +
> > + list_for_each_entry_safe(fd, nfd, &discard_data_list, efd_list) {
> > + mb_free_blocks(NULL, e4b, fd->efd_start_cluster, fd->efd_count);
> > + kmem_cache_free(ext4_free_data_cachep, fd);
> > + }
> > +
> > return count;
> > }
> >
> > --
> > 2.20.1
> >
> --
> Jan Kara <[email protected]>
> SUSE Labs, CR
On Tue 09-01-24 19:28:07, Fengnan Chang wrote:
> Jan Kara <[email protected]> 于2024年1月9日周二 01:15写道：
> >
> > On Fri 01-09-23 17:28:20, Fengnan Chang wrote:
> > > In commit a015434480dc("ext4: send parallel discards on commit
> > > completions"), issue all discard commands in parallel make all
> > > bios could merged into one request, so lowlevel drive can issue
> > > multi segments in one time which is more efficiency, but commit
> > > 55cdd0af2bc5 ("ext4: get discard out of jbd2 commit kthread contex")
> > > seems broke this way, let's fix it.
> > >
> > > In my test:
> > > 1. create 10 normal files, each file size is 10G.
> > > 2. deallocate file, punch a 16k holes every 32k.
> > > 3. trim all fs.
> > > the time of fstrim fs reduce from 6.7s to 1.3s.
> > >
> > > Signed-off-by: Fengnan Chang <[email protected]>
> >
> > This seems to have fallen through the cracks... I'm sorry for that.
> >
> > > static int ext4_try_to_trim_range(struct super_block *sb,
> > > struct ext4_buddy *e4b, ext4_grpblk_t start,
> > > ext4_grpblk_t max, ext4_grpblk_t minblocks)
> > > __acquires(ext4_group_lock_ptr(sb, e4b->bd_group))
> > > __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> > > {
> > > - ext4_grpblk_t next, count, free_count;
> > > + ext4_grpblk_t next, count, free_count, bak;
> > > void *bitmap;
> > > + struct ext4_free_data *entry = NULL, *fd, *nfd;
> > > + struct list_head discard_data_list;
> > > + struct bio *discard_bio = NULL;
> > > + struct blk_plug plug;
> > > + ext4_group_t group = e4b->bd_group;
> > > + struct ext4_free_extent ex;
> > > + bool noalloc = false;
> > > + int ret = 0;
> > > +
> > > + INIT_LIST_HEAD(&discard_data_list);
> > >
> > > bitmap = e4b->bd_bitmap;
> > > start = max(e4b->bd_info->bb_first_free, start);
> > > count = 0;
> > > free_count = 0;
> > >
> > > + blk_start_plug(&plug);
> > > while (start <= max) {
> > > start = mb_find_next_zero_bit(bitmap, max + 1, start);
> > > if (start > max)
> > > break;
> > > + bak = start;
> > > next = mb_find_next_bit(bitmap, max + 1, start);
> > > -
> > > if ((next - start) >= minblocks) {
> > > - int ret = ext4_trim_extent(sb, start, next - start, e4b);
> > > + /* when only one segment, there is no need to alloc entry */
> > > + noalloc = (free_count == 0) && (next >= max);
> >
> > Is the single extent case really worth the complications to save one
> > allocation? I don't think it is but maybe I'm missing something. Otherwise
> > the patch looks good to me!
> yeah, it's necessary, if there is only one segment, alloc memory may cause
> performance regression.
> Refer to this https://lore.kernel.org/linux-ext4/CALWNXx-6y0=ZDBMicv2qng9pKHWcpJbCvUm9TaRBwg81WzWkWQ@mail.gmail.com/
Ah, thanks for the reference! Then what I'd suggest is something like:
struct ext4_free_data first_entry;
/*
* We preallocate the first entry on stack to optimize for the common
* case of trimming single extent in each group. It has measurable
* performance impact.
*/
struct ext4_free_data *entry = &first_entry;
then when we allocate we do:
if (!entry)
entry = kmem_cache_alloc(...)
entry->efd_start_cluster = start;
entry->efd_count = next - start;
list_add_tail(&entry->efd_list, &discard_data_list);
entry = NULL;
and then when freeing we can have:
list_for_each_entry_safe(fd, nfd, &discard_data_list, efd_list) {
mb_free_blocks(NULL, e4b, fd->efd_start_cluster, fd->efd_count);
if (fd != &first_entry)
kmem_cache_free(ext4_free_data_cachep, fd);
}
Then it is more understandable what's going on...
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR
Jan Kara <[email protected]> 于2024年1月9日周二 20:09写道：
>
> On Tue 09-01-24 19:28:07, Fengnan Chang wrote:
> > Jan Kara <[email protected]> 于2024年1月9日周二 01:15写道：
> > >
> > > On Fri 01-09-23 17:28:20, Fengnan Chang wrote:
> > > > In commit a015434480dc("ext4: send parallel discards on commit
> > > > completions"), issue all discard commands in parallel make all
> > > > bios could merged into one request, so lowlevel drive can issue
> > > > multi segments in one time which is more efficiency, but commit
> > > > 55cdd0af2bc5 ("ext4: get discard out of jbd2 commit kthread contex")
> > > > seems broke this way, let's fix it.
> > > >
> > > > In my test:
> > > > 1. create 10 normal files, each file size is 10G.
> > > > 2. deallocate file, punch a 16k holes every 32k.
> > > > 3. trim all fs.
> > > > the time of fstrim fs reduce from 6.7s to 1.3s.
> > > >
> > > > Signed-off-by: Fengnan Chang <[email protected]>
> > >
> > > This seems to have fallen through the cracks... I'm sorry for that.
> > >
> > > > static int ext4_try_to_trim_range(struct super_block *sb,
> > > > struct ext4_buddy *e4b, ext4_grpblk_t start,
> > > > ext4_grpblk_t max, ext4_grpblk_t minblocks)
> > > > __acquires(ext4_group_lock_ptr(sb, e4b->bd_group))
> > > > __releases(ext4_group_lock_ptr(sb, e4b->bd_group))
> > > > {
> > > > - ext4_grpblk_t next, count, free_count;
> > > > + ext4_grpblk_t next, count, free_count, bak;
> > > > void *bitmap;
> > > > + struct ext4_free_data *entry = NULL, *fd, *nfd;
> > > > + struct list_head discard_data_list;
> > > > + struct bio *discard_bio = NULL;
> > > > + struct blk_plug plug;
> > > > + ext4_group_t group = e4b->bd_group;
> > > > + struct ext4_free_extent ex;
> > > > + bool noalloc = false;
> > > > + int ret = 0;
> > > > +
> > > > + INIT_LIST_HEAD(&discard_data_list);
> > > >
> > > > bitmap = e4b->bd_bitmap;
> > > > start = max(e4b->bd_info->bb_first_free, start);
> > > > count = 0;
> > > > free_count = 0;
> > > >
> > > > + blk_start_plug(&plug);
> > > > while (start <= max) {
> > > > start = mb_find_next_zero_bit(bitmap, max + 1, start);
> > > > if (start > max)
> > > > break;
> > > > + bak = start;
> > > > next = mb_find_next_bit(bitmap, max + 1, start);
> > > > -
> > > > if ((next - start) >= minblocks) {
> > > > - int ret = ext4_trim_extent(sb, start, next - start, e4b);
> > > > + /* when only one segment, there is no need to alloc entry */
> > > > + noalloc = (free_count == 0) && (next >= max);
> > >
> > > Is the single extent case really worth the complications to save one
> > > allocation? I don't think it is but maybe I'm missing something. Otherwise
> > > the patch looks good to me!
> > yeah, it's necessary, if there is only one segment, alloc memory may cause
> > performance regression.
> > Refer to this https://lore.kernel.org/linux-ext4/CALWNXx-6y0=ZDBMicv2qng9pKHWcpJbCvUm9TaRBwg81WzWkWQ@mail.gmail.com/
>
> Ah, thanks for the reference! Then what I'd suggest is something like:
>
> struct ext4_free_data first_entry;
> /*
> * We preallocate the first entry on stack to optimize for the common
> * case of trimming single extent in each group. It has measurable
> * performance impact.
> */
> struct ext4_free_data *entry = &first_entry;
>
> then when we allocate we do:
>
> if (!entry)
> entry = kmem_cache_alloc(...)
> entry->efd_start_cluster = start;
> entry->efd_count = next - start;
> list_add_tail(&entry->efd_list, &discard_data_list);
> entry = NULL;
>
> and then when freeing we can have:
>
> list_for_each_entry_safe(fd, nfd, &discard_data_list, efd_list) {
> mb_free_blocks(NULL, e4b, fd->efd_start_cluster, fd->efd_count);
> if (fd != &first_entry)
> kmem_cache_free(ext4_free_data_cachep, fd);
> }
>
> Then it is more understandable what's going on...
Looks better, I'll modify it in the next version.
Thanks.
>
> Honza
> --
> Jan Kara <[email protected]>
> SUSE Labs, CR