Commit Graph

11 Commits

Author SHA1 Message Date
Emilio G. Cota 78255ba2cc qht: drop ht argument from qht iterators
Accessing the HT from an iterator results almost always
in a deadlock. Given that only one qht-internal function
uses this argument, drop it from the interface.

Suggested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-09-26 08:55:54 -07:00
Emilio G. Cota ca8897a44c test-qht: speed up + test qht_resize
Perform first the tests that exercise code paths that are
easier to hit at small table sizes, and then resize the table
to speed up subsequent tests. If this resize is not too large,
we can make the test faster with no code coverage loss.

- With gcov enabled:

Before: 20.568s, 90.28% qht.c coverage
After:   5.168s, 93.06% qht.c coverage

The coverage increase is entirely due to calling qht_resize,
which we weren't calling before. Note that the code paths
that remain to be tested are either error handling or
can only occur when several threads are accessing the
hash table concurrently (e.g. seqlock retry, trylock fail).

- Without gcov:

Before: 1.987s
After:  0.528s

The speedup is almost the same as with gcov, although the
"before" run is a lot faster.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-09-26 08:55:54 -07:00
Emilio G. Cota 321a33f534 test-qht: test deletion of the last entry in a bucket
This improves coverage by one (!) LoC in qht.c, bringing the
coverage rate up from 90.00% to 90.28%.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-09-26 08:55:54 -07:00
Emilio G. Cota f44641bbf2 test-qht: test removal of non-existent entries
This improves qht.c code coverage from 89.44% to 90.00%.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-09-26 08:55:54 -07:00
Emilio G. Cota 922034e776 test-qht: test qht_iter_remove
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-09-26 08:55:54 -07:00
Emilio G. Cota 32359d529f qht: return existing entry when qht_insert fails
The meaning of "existing" is now changed to "matches in hash and
ht->cmp result". This is saner than just checking the pointer value.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by:  Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-06-15 07:42:55 -10:00
Emilio G. Cota 61b8cef1d4 qht: require a default comparison function
qht_lookup now uses the default cmp function. qht_lookup_custom is defined
to retain the old behaviour, that is a cmp function is explicitly provided.

qht_insert will gain use of the default cmp in the next patch.

Note that we move qht_lookup_custom's @func to be the last argument,
which makes the new qht_lookup as simple as possible.
Instead of this (i.e. keeping @func 2nd):
0000000000010750 <qht_lookup>:
   10750:       89 d1                   mov    %edx,%ecx
   10752:       48 89 f2                mov    %rsi,%rdx
   10755:       48 8b 77 08             mov    0x8(%rdi),%rsi
   10759:       e9 22 ff ff ff          jmpq   10680 <qht_lookup_custom>
   1075e:       66 90                   xchg   %ax,%ax

We get:
0000000000010740 <qht_lookup>:
   10740:       48 8b 4f 08             mov    0x8(%rdi),%rcx
   10744:       e9 37 ff ff ff          jmpq   10680 <qht_lookup_custom>
   10749:       0f 1f 80 00 00 00 00    nopl   0x0(%rax)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
2018-06-15 07:42:55 -10:00
Emilio G. Cota 9c7d64eb2a test-qht: perform lookups under rcu_read_lock
qht_lookup is meant to be called from an RCU read-critical
section. Make sure we're in such a section in test-qht
when performing lookups, despite the fact that no races
in qht can be triggered by test-qht since it is single-threaded.

Note that rcu_register_thread is already called by the
rcu_after_fork hook, and therefore duplicating it here would
be a bug.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1475706880-10667-4-git-send-email-cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-10-06 18:04:13 +02:00
Emilio G. Cota 7266ae91a1 qht: do not segfault when gathering stats from an uninitialized qht
So far, QHT functions assume that the passed qht has previously been
initialized--otherwise they segfault.

This patch makes an exception for qht_statistics_init, with the goal
of simplifying calling code. For instance, qht_statistics_init is
called from the 'info jit' dump, and given that under KVM the TB qht
is never initialized, we get a segfault. Thus, instead of complicating
the 'info jit' code with additional checks, let's allow passing an
uninitialized qht to qht_statistics_init.

While at it, add a test for this to test-qht.

Before the patch (for $ qemu -enable-kvm [...]):
(qemu) info jit
[...]
direct jump count   0 (0%) (2 jumps=0 0%)
Program received signal SIGSEGV, Segmentation fault.

After the patch the "TB hash buckets", "TB hash occupancy"
and "TB hash avg chain" lines are omitted.
(qemu) info jit
[...]
direct jump count   0 (0%) (2 jumps=0 0%)
TB hash buckets     0/0 (-nan% head buckets used)
TB hash occupancy   nan% avg chain occ. Histogram: (null)
TB hash avg chain   nan buckets. Histogram: (null)
[...]

Reported by: Changlong Xie <xiecl.fnst@cn.fujitsu.com>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1469205390-14369-1-git-send-email-cota@braap.org>
[Extract printing statistics to an entirely separate function. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-08-02 12:03:58 +02:00
Paolo Bonzini e9abfcb57f clean-includes: run it once more
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-06-16 18:39:03 +02:00
Emilio G. Cota 1a95404fbd qht: add test program
Acked-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <1465412133-3029-12-git-send-email-cota@braap.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
2016-06-11 23:10:20 +00:00