> libcfs in lustre has a resizeable hashtable. > Linux already has a resizeable hashtable, rhashtable, which is better > is most metrics. See https://lwn.net/Articles/751374/ in a few days > for an introduction to rhashtable.
Thansk for starting this work. I was think about cleaning the libcfs hash but your port to rhashtables is way better. How did you gather metrics to see that rhashtable was better than libcfs hash? > This series converts lustre to use rhashtable. This affects several > different tables, and each is different is various ways. > > There are two outstanding issues. One is that a bug in rhashtable > means that we cannot enable auto-shrinking in one of the tables. That > is documented as appropriate and should be fixed soon. > > The other is that rhashtable has an atomic_t which counts the elements > in a hash table. At least one table in lustre went to some trouble to > avoid any table-wide atomics, so that could lead to a regression. > I'm hoping that rhashtable can be enhanced with the option of a > per-cpu counter, or similar. > This doesn't sound quite ready to land just yet. This will have to do some soak testing and a larger scope of test to make sure no new regressions happen. Believe me I did work to make lustre work better on tickless systems, which I'm preparing for the linux client, and small changes could break things in interesting ways. I will port the rhashtable change to the Intel developement branch and get people more familar with the hash code to look at it. > I have enabled automatic shrinking on all tables where it makes sense > and doesn't trigger the bug. I have also removed all hints concerning > min/max size - I cannot see how these could be useful. > > The dump_pgcache debugfs file provided some interesting challenges. I > think I have cleaned it up enough so that it all makes sense. An > extra pair of eyes examining that code in particular would be > appreciated. > > This series passes all the same tests that pass before the patches are > applied. > > Thanks, > NeilBrown > > > --- > > NeilBrown (20): > staging: lustre: ptlrpc: convert conn_hash to rhashtable > staging: lustre: convert lov_pool to use rhashtable > staging: lustre: convert obd uuid hash to rhashtable > staging: lustre: convert osc_quota hash to rhashtable > staging: lustre: separate buckets from ldlm hash table > staging: lustre: ldlm: add a counter to the per-namespace data > staging: lustre: ldlm: store name directly in namespace. > staging: lustre: simplify ldlm_ns_hash_defs > staging: lustre: convert ldlm_resource hash to rhashtable. > staging: lustre: make struct lu_site_bkt_data private > staging: lustre: lu_object: discard extra lru count. > staging: lustre: lu_object: factor out extra per-bucket data > staging: lustre: lu_object: move retry logic inside htable_lookup > staging: lustre: fold lu_object_new() into lu_object_find_at() > staging: lustre: llite: use more private data in dump_pgcache > staging: lustre: llite: remove redundant lookup in dump_pgcache > staging: lustre: use call_rcu() to free lu_object_headers > staging: lustre: change how "dump_page_cache" walks a hash table > staging: lustre: convert lu_object cache to rhashtable > staging: lustre: remove cfs_hash resizeable hashtable implementation. > > > .../staging/lustre/include/linux/libcfs/libcfs.h | 1 > .../lustre/include/linux/libcfs/libcfs_hash.h | 866 -------- > drivers/staging/lustre/lnet/libcfs/Makefile | 2 > drivers/staging/lustre/lnet/libcfs/hash.c | 2064 > -------------------- > drivers/staging/lustre/lnet/libcfs/module.c | 12 > drivers/staging/lustre/lustre/include/lu_object.h | 55 - > drivers/staging/lustre/lustre/include/lustre_dlm.h | 19 > .../staging/lustre/lustre/include/lustre_export.h | 2 > drivers/staging/lustre/lustre/include/lustre_net.h | 4 > drivers/staging/lustre/lustre/include/obd.h | 11 > .../staging/lustre/lustre/include/obd_support.h | 9 > drivers/staging/lustre/lustre/ldlm/ldlm_request.c | 31 > drivers/staging/lustre/lustre/ldlm/ldlm_resource.c | 370 +--- > drivers/staging/lustre/lustre/llite/lcommon_cl.c | 8 > drivers/staging/lustre/lustre/llite/vvp_dev.c | 332 +-- > drivers/staging/lustre/lustre/llite/vvp_object.c | 9 > drivers/staging/lustre/lustre/lov/lov_internal.h | 11 > drivers/staging/lustre/lustre/lov/lov_obd.c | 12 > drivers/staging/lustre/lustre/lov/lov_object.c | 8 > drivers/staging/lustre/lustre/lov/lov_pool.c | 159 +- > drivers/staging/lustre/lustre/lov/lovsub_object.c | 9 > drivers/staging/lustre/lustre/obdclass/genops.c | 34 > drivers/staging/lustre/lustre/obdclass/lu_object.c | 564 ++--- > .../staging/lustre/lustre/obdclass/obd_config.c | 161 +- > .../staging/lustre/lustre/obdecho/echo_client.c | 8 > drivers/staging/lustre/lustre/osc/osc_internal.h | 5 > drivers/staging/lustre/lustre/osc/osc_quota.c | 136 - > drivers/staging/lustre/lustre/osc/osc_request.c | 12 > drivers/staging/lustre/lustre/ptlrpc/connection.c | 164 +- > 29 files changed, 870 insertions(+), 4208 deletions(-) > delete mode 100644 drivers/staging/lustre/include/linux/libcfs/libcfs_hash.h > delete mode 100644 drivers/staging/lustre/lnet/libcfs/hash.c > > -- > Signature > >