Re: [Qemu-devel] [PATCH 01/16] qht: require a default comparison function

["Alex Bennée" <alex.bennee@linaro.org>]

Emilio G. Cota <cota@braap.org> writes:

> 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.
>
> Signed-off-by: Emilio G. Cota <cota@braap.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  accel/tcg/cpu-exec.c      |  4 ++--
>  accel/tcg/translate-all.c | 16 +++++++++++++++-
>  include/qemu/qht.h        | 23 +++++++++++++++++++----
>  tests/qht-bench.c         | 14 +++++++-------
>  tests/test-qht.c          | 15 ++++++++++-----
>  util/qht.c                | 14 +++++++++++---
>  6 files changed, 64 insertions(+), 22 deletions(-)
>
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 280200f..ec57564 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -293,7 +293,7 @@ struct tb_desc {
>      uint32_t trace_vcpu_dstate;
>  };
>
> -static bool tb_cmp(const void *p, const void *d)
> +static bool tb_lookup_cmp(const void *p, const void *d)
>  {
>      const TranslationBlock *tb = p;
>      const struct tb_desc *desc = d;
> @@ -338,7 +338,7 @@ TranslationBlock *tb_htable_lookup(CPUState *cpu, target_ulong pc,
>      phys_pc = get_page_addr_code(desc.env, pc);
>      desc.phys_page1 = phys_pc & TARGET_PAGE_MASK;
>      h = tb_hash_func(phys_pc, pc, flags, cf_mask, *cpu->trace_dstate);
> -    return qht_lookup(&tb_ctx.htable, tb_cmp, &desc, h);
> +    return qht_lookup_custom(&tb_ctx.htable, tb_lookup_cmp, &desc, h);
>  }
>
>  void tb_set_jmp_target(TranslationBlock *tb, int n, uintptr_t addr)
> diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
> index 67795cd..1cf10f8 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -785,11 +785,25 @@ static inline void code_gen_alloc(size_t tb_size)
>      qemu_mutex_init(&tb_ctx.tb_lock);
>  }
>
> +static bool tb_cmp(const void *ap, const void *bp)
> +{
> +    const TranslationBlock *a = ap;
> +    const TranslationBlock *b = bp;
> +
> +    return a->pc == b->pc &&
> +        a->cs_base == b->cs_base &&
> +        a->flags == b->flags &&
> +        (tb_cflags(a) & CF_HASH_MASK) == (tb_cflags(b) & CF_HASH_MASK) &&
> +        a->trace_vcpu_dstate == b->trace_vcpu_dstate &&
> +        a->page_addr[0] == b->page_addr[0] &&
> +        a->page_addr[1] == b->page_addr[1];
> +}
> +
>  static void tb_htable_init(void)
>  {
>      unsigned int mode = QHT_MODE_AUTO_RESIZE;
>
> -    qht_init(&tb_ctx.htable, CODE_GEN_HTABLE_SIZE, mode);
> +    qht_init(&tb_ctx.htable, tb_cmp, CODE_GEN_HTABLE_SIZE, mode);
>  }
>
>  /* Must be called before using the QEMU cpus. 'tb_size' is the size
> diff --git a/include/qemu/qht.h b/include/qemu/qht.h
> index 531aa95..dd512bf 100644
> --- a/include/qemu/qht.h
> +++ b/include/qemu/qht.h
> @@ -11,8 +11,11 @@
>  #include "qemu/thread.h"
>  #include "qemu/qdist.h"
>
> +typedef bool (*qht_cmp_func_t)(const void *a, const void *b);
> +
>  struct qht {
>      struct qht_map *map;
> +    qht_cmp_func_t cmp;
>      QemuMutex lock; /* serializes setters of ht->map */
>      unsigned int mode;
>  };
> @@ -47,10 +50,12 @@ typedef void (*qht_iter_func_t)(struct qht *ht, void *p, uint32_t h, void *up);
>  /**
>   * qht_init - Initialize a QHT
>   * @ht: QHT to be initialized
> + * @cmp: default comparison function. Cannot be NULL.
>   * @n_elems: number of entries the hash table should be optimized for.
>   * @mode: bitmask with OR'ed QHT_MODE_*
>   */
> -void qht_init(struct qht *ht, size_t n_elems, unsigned int mode);
> +void qht_init(struct qht *ht, qht_cmp_func_t cmp, size_t n_elems,
> +              unsigned int mode);
>
>  /**
>   * qht_destroy - destroy a previously initialized QHT
> @@ -78,7 +83,7 @@ void qht_destroy(struct qht *ht);
>  bool qht_insert(struct qht *ht, void *p, uint32_t hash);
>
>  /**
> - * qht_lookup - Look up a pointer in a QHT
> + * qht_lookup_custom - Look up a pointer using a custom comparison function.
>   * @ht: QHT to be looked up
>   * @func: function to compare existing pointers against @userp
>   * @userp: pointer to pass to @func
> @@ -94,8 +99,18 @@ bool qht_insert(struct qht *ht, void *p, uint32_t hash);
>   * Returns the corresponding pointer when a match is found.
>   * Returns NULL otherwise.
>   */
> -void *qht_lookup(struct qht *ht, qht_lookup_func_t func, const void *userp,
> -                 uint32_t hash);
> +void *qht_lookup_custom(struct qht *ht, qht_lookup_func_t func,
> +                        const void *userp, uint32_t hash);
> +
> +/**
> + * qht_lookup - Look up a pointer in a QHT
> + * @ht: QHT to be looked up
> + * @userp: pointer to pass to @func
> + * @hash: hash of the pointer to be looked up
> + *
> + * Calls qht_lookup_custom() using @ht's default comparison function.
> + */
> +void *qht_lookup(struct qht *ht, const void *userp, uint32_t hash);
>
>  /**
>   * qht_remove - remove a pointer from the hash table
> diff --git a/tests/qht-bench.c b/tests/qht-bench.c
> index 4cabdfd..c94ac25 100644
> --- a/tests/qht-bench.c
> +++ b/tests/qht-bench.c
> @@ -93,10 +93,10 @@ static void usage_complete(int argc, char *argv[])
>      exit(-1);
>  }
>
> -static bool is_equal(const void *obj, const void *userp)
> +static bool is_equal(const void *ap, const void *bp)
>  {
> -    const long *a = obj;
> -    const long *b = userp;
> +    const long *a = ap;
> +    const long *b = bp;
>
>      return *a == *b;
>  }
> @@ -150,7 +150,7 @@ static void do_rw(struct thread_info *info)
>
>          p = &keys[info->r & (lookup_range - 1)];
>          hash = h(*p);
> -        read = qht_lookup(&ht, is_equal, p, hash);
> +        read = qht_lookup(&ht, p, hash);
>          if (read) {
>              stats->rd++;
>          } else {
> @@ -162,7 +162,7 @@ static void do_rw(struct thread_info *info)
>          if (info->write_op) {
>              bool written = false;
>
> -            if (qht_lookup(&ht, is_equal, p, hash) == NULL) {
> +            if (qht_lookup(&ht, p, hash) == NULL) {
>                  written = qht_insert(&ht, p, hash);
>              }
>              if (written) {
> @@ -173,7 +173,7 @@ static void do_rw(struct thread_info *info)
>          } else {
>              bool removed = false;
>
> -            if (qht_lookup(&ht, is_equal, p, hash)) {
> +            if (qht_lookup(&ht, p, hash)) {
>                  removed = qht_remove(&ht, p, hash);
>              }
>              if (removed) {
> @@ -308,7 +308,7 @@ static void htable_init(void)
>      }
>
>      /* initialize the hash table */
> -    qht_init(&ht, qht_n_elems, qht_mode);
> +    qht_init(&ht, is_equal, qht_n_elems, qht_mode);
>      assert(init_size <= init_range);
>
>      pr_params();
> diff --git a/tests/test-qht.c b/tests/test-qht.c
> index 9b7423a..f8f2886 100644
> --- a/tests/test-qht.c
> +++ b/tests/test-qht.c
> @@ -13,10 +13,10 @@
>  static struct qht ht;
>  static int32_t arr[N * 2];
>
> -static bool is_equal(const void *obj, const void *userp)
> +static bool is_equal(const void *ap, const void *bp)
>  {
> -    const int32_t *a = obj;
> -    const int32_t *b = userp;
> +    const int32_t *a = ap;
> +    const int32_t *b = bp;
>
>      return *a == *b;
>  }
> @@ -60,7 +60,12 @@ static void check(int a, int b, bool expected)
>
>          val = i;
>          hash = i;
> -        p = qht_lookup(&ht, is_equal, &val, hash);
> +        /* test both lookup variants; results should be the same */
> +        if (i % 2) {
> +            p = qht_lookup(&ht, &val, hash);
> +        } else {
> +            p = qht_lookup_custom(&ht, is_equal, &val, hash);
> +        }
>          g_assert_true(!!p == expected);
>      }
>      rcu_read_unlock();
> @@ -102,7 +107,7 @@ static void qht_do_test(unsigned int mode, size_t init_entries)
>      /* under KVM we might fetch stats from an uninitialized qht */
>      check_n(0);
>
> -    qht_init(&ht, 0, mode);
> +    qht_init(&ht, is_equal, 0, mode);
>
>      check_n(0);
>      insert(0, N);
> diff --git a/util/qht.c b/util/qht.c
> index ff4d2e6..dcb3ee1 100644
> --- a/util/qht.c
> +++ b/util/qht.c
> @@ -351,11 +351,14 @@ static struct qht_map *qht_map_create(size_t n_buckets)
>      return map;
>  }
>
> -void qht_init(struct qht *ht, size_t n_elems, unsigned int mode)
> +void qht_init(struct qht *ht, qht_cmp_func_t cmp, size_t n_elems,
> +              unsigned int mode)
>  {
>      struct qht_map *map;
>      size_t n_buckets = qht_elems_to_buckets(n_elems);
>
> +    g_assert(cmp);
> +    ht->cmp = cmp;
>      ht->mode = mode;
>      qemu_mutex_init(&ht->lock);
>      map = qht_map_create(n_buckets);
> @@ -479,8 +482,8 @@ void *qht_lookup__slowpath(struct qht_bucket *b, qht_lookup_func_t func,
>      return ret;
>  }
>
> -void *qht_lookup(struct qht *ht, qht_lookup_func_t func, const void *userp,
> -                 uint32_t hash)
> +void *qht_lookup_custom(struct qht *ht, qht_lookup_func_t func,
> +                        const void *userp, uint32_t hash)
>  {
>      struct qht_bucket *b;
>      struct qht_map *map;
> @@ -502,6 +505,11 @@ void *qht_lookup(struct qht *ht, qht_lookup_func_t func, const void *userp,
>      return qht_lookup__slowpath(b, func, userp, hash);
>  }
>
> +void *qht_lookup(struct qht *ht, const void *userp, uint32_t hash)
> +{
> +    return qht_lookup_custom(ht, ht->cmp, userp, hash);
> +}
> +
>  /* call with head->lock held */
>  static bool qht_insert__locked(struct qht *ht, struct qht_map *map,
>                                 struct qht_bucket *head, void *p, uint32_t hash,


--
Alex Bennée