| Message ID | 20211103145122.17338-2-lczerner@redhat.com |
|---|---|
| State | Awaiting Upstream |
| Headers | show |
| Series | [1/2] ext4: Change s_last_trim_minblks type to unsigned long | expand |
On Nov 3, 2021, at 8:51 AM, Lukas Czerner <lczerner@redhat.com> wrote: > > Ext4 has an optimization mechanism for batched disacrd (FITRIM) that > should help speed up subsequent calls of FITRIM ioctl by skipping the > groups that were previously trimmed. However because the FITRIM allows > to set the minimum size of an extent to trim, ext4 stores the last > minimum extent size and only avoids trimming the group if it was > previously trimmed with minimum extent size equal to, or smaller than > the current call. > > There is currently no way to bypass the optimization without > umount/mount cycle. This becomes a problem when the file system is > live migrated to a different storage, because the optimization will > prevent possibly useful discard calls to the storage. > > Fix it by exporting the s_last_trim_minblks via sysfs interface which > will allow us to set the minimum size to the number of blocks larger > than subsequent FITRIM call, effectively bypassing the optimization. > > By setting the s_last_trim_minblks to ULONG_MAX the optimization will be > effectively cleared regardless of the previous state, or file system > configuration. > > For example: > getconf ULONG_MAX > /sys/fs/ext4/dm-1/last_trim_minblks > > Signed-off-by: Lukas Czerner <lczerner@redhat.com> > Reported-by: Laurent GUERBY <laurent@guerby.net> Reviewed-by: Andreas Dilger <adilger@dilger.ca> > --- > v2: Remove unnecessary assignment > v3: s_last_trim_minblks is now unsinged long which simplifies this > > fs/ext4/sysfs.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c > index 2314f7446592..95d8a996d2d8 100644 > --- a/fs/ext4/sysfs.c > +++ b/fs/ext4/sysfs.c > @@ -245,6 +245,7 @@ EXT4_ATTR(last_error_time, 0444, last_error_time); > EXT4_ATTR(journal_task, 0444, journal_task); > EXT4_RW_ATTR_SBI_UI(mb_prefetch, s_mb_prefetch); > EXT4_RW_ATTR_SBI_UI(mb_prefetch_limit, s_mb_prefetch_limit); > +EXT4_RW_ATTR_SBI_UL(last_trim_minblks, s_last_trim_minblks); > > static unsigned int old_bump_val = 128; > EXT4_ATTR_PTR(max_writeback_mb_bump, 0444, pointer_ui, &old_bump_val); > @@ -295,6 +296,7 @@ static struct attribute *ext4_attrs[] = { > #endif > ATTR_LIST(mb_prefetch), > ATTR_LIST(mb_prefetch_limit), > + ATTR_LIST(last_trim_minblks), > NULL, > }; > ATTRIBUTE_GROUPS(ext4); > -- > 2.31.1 > Cheers, Andreas
ping -Lukas On Wed, Nov 03, 2021 at 03:51:22PM +0100, Lukas Czerner wrote: > Ext4 has an optimization mechanism for batched disacrd (FITRIM) that > should help speed up subsequent calls of FITRIM ioctl by skipping the > groups that were previously trimmed. However because the FITRIM allows > to set the minimum size of an extent to trim, ext4 stores the last > minimum extent size and only avoids trimming the group if it was > previously trimmed with minimum extent size equal to, or smaller than > the current call. > > There is currently no way to bypass the optimization without > umount/mount cycle. This becomes a problem when the file system is > live migrated to a different storage, because the optimization will > prevent possibly useful discard calls to the storage. > > Fix it by exporting the s_last_trim_minblks via sysfs interface which > will allow us to set the minimum size to the number of blocks larger > than subsequent FITRIM call, effectively bypassing the optimization. > > By setting the s_last_trim_minblks to ULONG_MAX the optimization will be > effectively cleared regardless of the previous state, or file system > configuration. > > For example: > getconf ULONG_MAX > /sys/fs/ext4/dm-1/last_trim_minblks > > Signed-off-by: Lukas Czerner <lczerner@redhat.com> > Reported-by: Laurent GUERBY <laurent@guerby.net> > --- > v2: Remove unnecessary assignment > v3: s_last_trim_minblks is now unsinged long which simplifies this > > fs/ext4/sysfs.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c > index 2314f7446592..95d8a996d2d8 100644 > --- a/fs/ext4/sysfs.c > +++ b/fs/ext4/sysfs.c > @@ -245,6 +245,7 @@ EXT4_ATTR(last_error_time, 0444, last_error_time); > EXT4_ATTR(journal_task, 0444, journal_task); > EXT4_RW_ATTR_SBI_UI(mb_prefetch, s_mb_prefetch); > EXT4_RW_ATTR_SBI_UI(mb_prefetch_limit, s_mb_prefetch_limit); > +EXT4_RW_ATTR_SBI_UL(last_trim_minblks, s_last_trim_minblks); > > static unsigned int old_bump_val = 128; > EXT4_ATTR_PTR(max_writeback_mb_bump, 0444, pointer_ui, &old_bump_val); > @@ -295,6 +296,7 @@ static struct attribute *ext4_attrs[] = { > #endif > ATTR_LIST(mb_prefetch), > ATTR_LIST(mb_prefetch_limit), > + ATTR_LIST(last_trim_minblks), > NULL, > }; > ATTRIBUTE_GROUPS(ext4); > -- > 2.31.1 >
On Wed, 3 Nov 2021 15:51:22 +0100, Lukas Czerner wrote: > Ext4 has an optimization mechanism for batched disacrd (FITRIM) that > should help speed up subsequent calls of FITRIM ioctl by skipping the > groups that were previously trimmed. However because the FITRIM allows > to set the minimum size of an extent to trim, ext4 stores the last > minimum extent size and only avoids trimming the group if it was > previously trimmed with minimum extent size equal to, or smaller than > the current call. > > [...] Applied, thanks! [2/2] ext4: Allow to change s_last_trim_minblks via sysfs commit: db19c4cdc28a8ec1241d50656991ab1bd96f5c02 Best regards,
diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c index 2314f7446592..95d8a996d2d8 100644 --- a/fs/ext4/sysfs.c +++ b/fs/ext4/sysfs.c @@ -245,6 +245,7 @@ EXT4_ATTR(last_error_time, 0444, last_error_time); EXT4_ATTR(journal_task, 0444, journal_task); EXT4_RW_ATTR_SBI_UI(mb_prefetch, s_mb_prefetch); EXT4_RW_ATTR_SBI_UI(mb_prefetch_limit, s_mb_prefetch_limit); +EXT4_RW_ATTR_SBI_UL(last_trim_minblks, s_last_trim_minblks); static unsigned int old_bump_val = 128; EXT4_ATTR_PTR(max_writeback_mb_bump, 0444, pointer_ui, &old_bump_val); @@ -295,6 +296,7 @@ static struct attribute *ext4_attrs[] = { #endif ATTR_LIST(mb_prefetch), ATTR_LIST(mb_prefetch_limit), + ATTR_LIST(last_trim_minblks), NULL, }; ATTRIBUTE_GROUPS(ext4);
Ext4 has an optimization mechanism for batched disacrd (FITRIM) that should help speed up subsequent calls of FITRIM ioctl by skipping the groups that were previously trimmed. However because the FITRIM allows to set the minimum size of an extent to trim, ext4 stores the last minimum extent size and only avoids trimming the group if it was previously trimmed with minimum extent size equal to, or smaller than the current call. There is currently no way to bypass the optimization without umount/mount cycle. This becomes a problem when the file system is live migrated to a different storage, because the optimization will prevent possibly useful discard calls to the storage. Fix it by exporting the s_last_trim_minblks via sysfs interface which will allow us to set the minimum size to the number of blocks larger than subsequent FITRIM call, effectively bypassing the optimization. By setting the s_last_trim_minblks to ULONG_MAX the optimization will be effectively cleared regardless of the previous state, or file system configuration. For example: getconf ULONG_MAX > /sys/fs/ext4/dm-1/last_trim_minblks Signed-off-by: Lukas Czerner <lczerner@redhat.com> Reported-by: Laurent GUERBY <laurent@guerby.net> --- v2: Remove unnecessary assignment v3: s_last_trim_minblks is now unsinged long which simplifies this fs/ext4/sysfs.c | 2 ++ 1 file changed, 2 insertions(+)