Re: [PATCH v4 8/8] xfs: add background scanning to clear EOFBLOCKS inodes

Brian Foster
2012-09-28T20:42:51Z

On 09/28/2012 04:00 AM, Dave Chinner wrote:
> On Thu, Sep 27, 2012 at 01:45:52PM -0400, Brian Foster wrote:
>> Create a delayed_work to enable background scanning and freeing
>> of EOFBLOCKS inodes. The scanner kicks in once speculative
>> preallocation occurs and stops requeueing itself when no EOFBLOCKS
>> inodes exist.
>>
>> Scans are queued on the existing syncd workqueue and the interval
>> is based on the new eofb_timer tunable (default to 5m). The
>> background scanner performs unfiltered, best effort scans (which
>> skips inodes under lock contention or with a dirty cache mapping).
>>
>> Signed-off-by: Brian Foster <bfoster@redhat.com>
>> ---
>> fs/xfs/xfs_globals.c | 1 +
>> fs/xfs/xfs_linux.h | 1 +
>> fs/xfs/xfs_mount.h | 2 ++
>> fs/xfs/xfs_sync.c | 30 ++++++++++++++++++++++++++++++
>> fs/xfs/xfs_sysctl.c | 9 +++++++++
>> fs/xfs/xfs_sysctl.h | 1 +
>> 6 files changed, 44 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_globals.c b/fs/xfs/xfs_globals.c
>> index 76e81cf..fda9a66 100644
>> --- a/fs/xfs/xfs_globals.c
>> +++ b/fs/xfs/xfs_globals.c
>> @@ -40,4 +40,5 @@ xfs_param_t xfs_params = {
>> .rotorstep = { 1, 1, 255 },
>> .inherit_nodfrg = { 0, 1, 1 },
>> .fstrm_timer = { 1, 30*100, 3600*100},
>> + .eofb_timer = { 1*100, 300*100, 7200*100},
>> };
>> diff --git a/fs/xfs/xfs_linux.h b/fs/xfs/xfs_linux.h
>> index 828662f..bbad99b 100644
>> --- a/fs/xfs/xfs_linux.h
>> +++ b/fs/xfs/xfs_linux.h
>> @@ -118,6 +118,7 @@
>> #define xfs_rotorstep xfs_params.rotorstep.val
>> #define xfs_inherit_nodefrag xfs_params.inherit_nodfrg.val
>> #define xfs_fstrm_centisecs xfs_params.fstrm_timer.val
>> +#define xfs_eofb_centisecs xfs_params.eofb_timer.val
>
> Let's not propagate that stupid "centiseconds" unit any further.
> Nobody uses it, and it was only introduced because jiffie was 10ms
> and there were 100 to a second so it was easy to convert in the
> code. I don't think there is any reason for needing sub-second
> granularity for this background function, so seconds shoul dbe just
> fine for it. If you think we nee dfiner granularity, milliseconds is
> the nex tunit to choose....
>

I think seconds is fine. I chose 1s for a minimum, but even that is
pathological and really only useful for focused stress testing.

>>
>> #define current_cpu() (raw_smp_processor_id())
>> #define current_pid() (current->pid)
>> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
>> index deee09e..bf5ecfa 100644
>> --- a/fs/xfs/xfs_mount.h
>> +++ b/fs/xfs/xfs_mount.h
>> @@ -199,6 +199,8 @@ typedef struct xfs_mount {
>> struct xfs_mru_cache *m_filestream; /* per-mount filestream data */
>> struct delayed_work m_sync_work; /* background sync work */
>> struct delayed_work m_reclaim_work; /* background inode reclaim */
>> + struct delayed_work m_eofblocks_work; /* background eof blocks
>> + trimming */
>> struct work_struct m_flush_work; /* background inode flush */
>> __int64_t m_update_flags; /* sb flags we need to update
>> on the next remount,rw */
>> diff --git a/fs/xfs/xfs_sync.c b/fs/xfs/xfs_sync.c
>> index c9e1c16..31f678a 100644
>> --- a/fs/xfs/xfs_sync.c
>> +++ b/fs/xfs/xfs_sync.c
>> @@ -532,6 +532,31 @@ xfs_flush_worker(
>> xfs_sync_data(mp, SYNC_TRYLOCK | SYNC_WAIT);
>> }
>>
>> +/*
>> + * Background scanning to trim post-EOF preallocated space. This is queued
>> + * based on the 'eofb_centisecs' tunable (5m by default).
>> + */
>> +STATIC void
>> +xfs_queue_eofblocks(
>> + struct xfs_mount *mp)
>> +{
>> + rcu_read_lock();
>> + if (radix_tree_tagged(&mp->m_perag_tree, XFS_ICI_EOFBLOCKS_TAG))
>> + queue_delayed_work(xfs_syncd_wq, &mp->m_eofblocks_work,
>> + msecs_to_jiffies(xfs_eofb_centisecs * 10));
>> + rcu_read_unlock();
>> +}
>
> This will all need reworking for the new xfs_icache.c and per-mount
> workqueue structuring. Fundamentally there is nothing wrong with
> what you've done, it's just been reworked...
>
>> + {
>> + .procname = "eofb_centisecs",
>
> Ugh. Call it something users might understand. Say
> "background_prealloc_discard_period", or something similarly
> informative...
>

Ok. Thanks for the review.

Brian

> Cheers,
>
> Dave.