From Daniel Gryniewicz <dang@redhat.com>: Daniel Gryniewicz has uploaded this change for review. ( https://review.gerrithub.io/411313 Change subject: MDCACHE - Insert scanned entries differently ...................................................................... MDCACHE - Insert scanned entries differently When we're doing a readdir and the size of the directory is larger than the cache size, then a poor interaction between the LRU and the readdir could occur. When the cache is above high-water, and a new chunk is read, then the entries for the beginning of the chunk are created and inserted in LRU of L1. Later entries from the chunk recycle (because we're above high-water). If the L2 is empty (likely, if the readdir is early in the workload, or if it goes on long enough and recycles the enire L2), then the LRU of L1 is recycled. These, however, are likely to be the entries created earlier in the chunk. Then, when the readdir gets around to calling the callback for the upper layer, it has to do a lookup() and a getattr() on each entry. This causes a huge number of round-trips to the cluster, destroying performance. However, the current LRU behavior is desirable for many cases. If an entry is created, but not used immediately, we want it to fall out of the cache quickly. This fix distinguishes between entry creation from a scan and from other sources. Scan creations are inserted into the MRU of L2, rather than the LRU of L1. The downside of this is that 2 refs are necessary to move to MRU of L1. The upside is that entries from a readdir are recycled in FIFO order, rather than LIFO order, meaning that the cached entry will stick around long enough to be used in the readdir. Change-Id: I45e71106e66f7ba15b7b8635c7f67622fc751048 Signed-off-by: Daniel Gryniewicz <dang@redhat.com> --- M src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_handle.c M src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_helpers.c M src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_int.h M src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_lru.c M src/FSAL/Stackable_FSALs/FSAL_MDCACHE/mdcache_lru.h 5 files changed, 40 insertions(+), 16 deletions(-) git pull ssh://review.gerrithub.io:29418/ffilz/nfs-ganesha refs/changes/13/411313/1 -- To view, visit https://review.gerrithub.io/411313 To unsubscribe, or for help writing mail filters, visit https://review.gerrithub.io/settings Gerrit-Project: ffilz/nfs-ganesha Gerrit-Branch: next Gerrit-MessageType: newchange Gerrit-Change-Id: I45e71106e66f7ba15b7b8635c7f67622fc751048 Gerrit-Change-Number: 411313 Gerrit-PatchSet: 1 Gerrit-Owner: Daniel Gryniewicz <dang@redhat.com>