Re: [patch 0/5] refault distance-based file cache sizing

["nai.xia" <nai.xia@gmail.com>]

Hi Johannes,

Just out of curiosity(since I didn't study deep into the
reclaiming algorithms), I can recall from here that around 2005,
there was an(or some?) implementation of the "Clock-pro" algorithm
which also have the idea of "reuse distance", but it seems that algo
did not work well enough to get merged? Does this patch series finally
solve the problem(s) with "Clock-pro" or totally doesn't have to worry
about the similar problems?


Thanks,

Nai

On 2012/05/01 16:41, Johannes Weiner wrote:
> Hi,
>
> our file data caching implementation is done by having an inactive
> list of pages that have yet to prove worth keeping around and an
> active list of pages that already did.  The question is how to balance
> those two lists against each other.
>
> On one hand, the space for inactive pages needs to be big enough so
> that they have the necessary time in memory to gather the references
> required for an activation.  On the other hand, we want an active list
> big enough to hold all data that is frequently used, if possible, to
> protect it from streams of less frequently used/once used pages.
>
> Our current balancing ("active can't grow larger than inactive") does
> not really work too well.  We have people complaining that the working
> set is not well protected from used-once file cache, and other people
> complaining that we don't adapt to changes in the workingset and
> protect stale pages in other cases.
>
> This series stores file cache eviction information in the vacated page
> cache radix tree slots and uses it on refault to see if the pages
> currently on the active list need to have their status challenged.
>
> A fully activated file set that occupies 85% of memory is successfully
> detected as stale when another file set of equal size is accessed for
> a few times (4-5).  The old kernel would never adapt to the second
> one.  If the new set is bigger than memory, the old set is left
> untouched, where the old kernel would shrink the old set to half of
> memory and leave it at that.  Tested on a multi-zone single-node
> machine.
>
> More testing is obviously required, but I first wanted some opinions
> at this point.  Is there fundamental disagreement with the concept?
> With the implementation?
>
> Memcg hard limit reclaim is not converted (anymore, ripped it out to
> focus on the global case first) and it still does the 50/50 balancing
> between lists, but this will be re-added in the next version.
>
> Patches are based on 3.3.
>
>   fs/btrfs/compression.c     |   10 +-
>   fs/btrfs/extent_io.c       |    3 +-
>   fs/cachefiles/rdwr.c       |   26 +++--
>   fs/ceph/xattr.c            |    2 +-
>   fs/inode.c                 |    7 +-
>   fs/logfs/readwrite.c       |    9 +-
>   fs/nilfs2/inode.c          |    6 +-
>   fs/ntfs/file.c             |   11 ++-
>   fs/splice.c                |   10 +-
>   include/linux/mm.h         |    8 ++
>   include/linux/mmzone.h     |    7 ++
>   include/linux/pagemap.h    |   54 ++++++++---
>   include/linux/pagevec.h    |    3 +
>   include/linux/radix-tree.h |    4 -
>   include/linux/sched.h      |    1 +
>   include/linux/shmem_fs.h   |    1 +
>   include/linux/swap.h       |    7 ++
>   lib/radix-tree.c           |   75 ---------------
>   mm/Makefile                |    1 +
>   mm/filemap.c               |  222 ++++++++++++++++++++++++++++++++++----------
>   mm/memcontrol.c            |    3 +
>   mm/mincore.c               |   20 +++-
>   mm/page_alloc.c            |    7 ++
>   mm/readahead.c             |   51 +++++++++-
>   mm/shmem.c                 |   89 +++---------------
>   mm/swap.c                  |   23 +++++
>   mm/truncate.c              |   73 +++++++++++---
>   mm/vmscan.c                |   80 +++++++++-------
>   mm/vmstat.c                |    4 +
>   mm/workingset.c            |  174 ++++++++++++++++++++++++++++++++++
>   net/ceph/messenger.c       |    2 +-
>   net/ceph/pagelist.c        |    4 +-
>   net/ceph/pagevec.c         |    2 +-
>   33 files changed, 682 insertions(+), 317 deletions(-)
>
> Thanks,
> Johannes
>
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