3:44 p.m.
Hmm, what's the path to taking a ref without moving to MRU of L2 or LRU of L1?
There are a number of issues with sticky entries blowing the cache size coming up that
really need to be resolved.
I wonder if we should remove any entry with refcount >1 from the LRU, and note where we
should place it when refcount is reduced to 1. That would take out the pinned entries as
well as temporarily in use entries. The trick would be the refcount bump for the actual
LRU processing.
Frank
-----Original Message-----
From: Pradeep Thomas [mailto:pradeepthomas@gmail.com]
Sent: Thursday, June 23, 2022 1:36 PM
To: devel(a)lists.nfs-ganesha.org
Subject: [NFS-Ganesha-Devel] Unclaimable MDCache entries at the LRU end of
L2 queue.
Hello,
I'm hitting a scenario where the entry at the LRU end of L2 queue becomes
active. But we don't move it to L1 - likely because the entry becomes active in
the context of a readdir. The cache keeps growing to a point where kernel will
invoke oom killer to terminate ganesha process.
When we reap entries (lru_reap_impl), could we look beyond LRU end - perhaps
try a fixed number of entries? Another option is to garbage collect the L2 queue
also and free claimable entries beyond LRU end of the queue(through
mdcache_lru_release_entries()). Any other thoughts?
In the instance below, MDCache is supposed to be capped at 100K entries. But it
grows to > 5 million entries (~17*310K).
sudo gdb -q -p $(pidof ganesha.nfsd) -batch -ex 'p LRU[0].L1' -ex 'p
LRU[0].L2' -
ex 'p LRU[1].L1' -ex 'p LRU[1].L2' -ex 'p LRU[2].L1' -ex 'p
LRU[2].L2' -ex 'p
LRU[3].L1' -ex 'p LRU[3].L2' -ex 'p LRU[4].L1' -ex 'p
LRU[4].L2' -ex 'p LRU[5].L1' -
ex 'p LRU[5].L2' -ex 'p LRU[6].L1' -ex 'p LRU[6].L2'
$1 = {q = {next = 0x7fe16a6adc30, prev = 0x7fe066775d30}, id = LRU_ENTRY_L1,
size = 37}
$2 = {q = {next = 0x7fe0cd6d1130, prev = 0x7fdd595e2030}, id = LRU_ENTRY_L2,
size = 310609}
$3 = {q = {next = 0x7fe222cc7930, prev = 0x7fe0e8afaf30}, id = LRU_ENTRY_L1,
size = 37}
$4 = {q = {next = 0x7fdfa2022d30, prev = 0x7fe01c386b30}, id = LRU_ENTRY_L2,
size = 310459}
$5 = {q = {next = 0x7fdfdd8acb30, prev = 0x7fe233849b30}, id = LRU_ENTRY_L1,
size = 31}
$6 = {q = {next = 0x7fdf014e7e30, prev = 0x7fdd90fd7430}, id = LRU_ENTRY_L2,
size = 310297}
$7 = {q = {next = 0x7fde79a4f030, prev = 0x7fe233a4aa30}, id = LRU_ENTRY_L1,
size = 32}
$8 = {q = {next = 0x7fe061388430, prev = 0x7fdd24b5cf30}, id = LRU_ENTRY_L2,
size = 310659}
$9 = {q = {next = 0x7fe1e96ce430, prev = 0x7fe0b3b4b130}, id = LRU_ENTRY_L1,
size = 34}
$10 = {q = {next = 0x7fe00d84ff30, prev = 0x7fdd685b1530}, id =
LRU_ENTRY_L2, size = 310635}
$11 = {q = {next = 0x7fdf9df4fb30, prev = 0x7fe2414aaa30}, id = LRU_ENTRY_L1,
size = 33}
$12 = {q = {next = 0x7fe165e82d30, prev = 0x7fdf1d2b8a30}, id =
LRU_ENTRY_L2, size = 310566}
$13 = {q = {next = 0x7fe159e55a30, prev = 0x7fde3f973d30}, id =
LRU_ENTRY_L1, size = 41}
$14 = {q = {next = 0x7fdf4fbb9030, prev = 0x7fdea8ca0730}, id =
LRU_ENTRY_L2, size = 310460}
First entry has a ref of 2. But next entries are actually claimable.
sudo gdb -q -p $(pidof ganesha.nfsd) -batch -ex 'p *(mdcache_lru_t
*)LRU[0].L2.q.next'
$1 = {q = {next = 0x7fe0fbff0c30, prev = 0x7fe250de2960 <LRU+32>}, qid =
LRU_ENTRY_L2, refcnt = 2, flags = 0, lane = 0, cf = 0}
sudo gdb -q -p $(pidof ganesha.nfsd) -batch -ex 'p *(mdcache_lru_t
*)0x7fe0fbff0c30'
$1 = {q = {next = 0x7fe0c2c5a130, prev = 0x7fe0cd6d1130}, qid =
LRU_ENTRY_L2, refcnt = 1, flags = 0, lane = 0, cf = 0}
sudo gdb -q -p $(pidof ganesha.nfsd) -batch -ex 'p *(mdcache_lru_t
*)0x7fe0c2c5a130'
$1 = {q = {next = 0x7fe06dfeac30, prev = 0x7fe142936430}, qid =
LRU_ENTRY_L2, refcnt = 1, flags = 0, lane = 0, cf = 0}
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