Possible scalability improvement

[Percona]

In some workloads I see
OS WAIT ARRAY INFO: reservation count 8610679, signal count 6629259
--Thread 1281251648 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1279654208 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1290836288 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1285511488 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1271134528 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1285245248 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1289505088 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1276193088 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1291102528 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1272465728 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1276725568 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1278056768 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1286842688 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1288706368 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1280985408 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1284446528 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1287641408 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
--Thread 1282582848 has waited at btr0cur.c line 366 for 0.00 seconds the semaphore:
S-lock on RW-latch at 0x2aaab9220f20 created in file dict0dict.c line 3706
a writer (thread id 1276991808) has reserved it in mode exclusive
number of readers 0, s_waiters flag 1, x_waiters flag 0
Last time read locked in file btr0cur.c line 366
Last time write locked in file btr0cur.c line 359
Mutex spin waits 0, rounds 987864487, OS waits 3785934
RW-shared spins 6245018, OS waits 1592849; RW-excl spins 31917356, OS waits 1849597

which corresponds
to
        } else if (latch_mode == BTR_CONT_MODIFY_TREE) {
                /* Do nothing */
                ut_ad(mtr_memo_contains(mtr, dict_tree_get_lock(tree),
                                                        MTR_MEMO_X_LOCK));
        } else {
                mtr_s_lock(dict_tree_get_lock(tree), mtr);
        }

Can we improve this ?

[Yasufumi Kinoshita (yasufumi-kinoshita)]

This may be same to
https://bugs.launchpad.net/percona-patches/+bug/329005
I have registered it also to percona-patches.

[Yasufumi Kinoshita (yasufumi-kinoshita)]

This is same to (or part of) https://bugs.launchpad.net/percona-xtradb/+bug/329005 .
I have changed the priolity 329005 to High. And this report as duplicated.