On Thu, Feb 13, 2020 at 2:40 PM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote:
> According to profiling of semodule -BN, ebitmap_cardinality() is called
> quite often and contributes a lot to the total runtime. Cache its result
> in the ebitmap struct to reduce this overhead. The cached value is
> invalidated on most modifying operations, but ebitmap_cardinality() is
> usually called once the ebitmap doesn't change any more.
>
> After this patch, the time to do 'semodule -BN' on Fedora Rawhide has
> decreased from ~14.6s to ~12.4s (2.2s saved).
I have no idea why, but I'm now getting completely different times
(10.9s vs. 8.9s) with the same builds on the same setup... I can no
longer reproduce the slower times anywhere (F31/locally/...) so I have
to assume it was some kind of glitch. Since the numbers show a similar
magnitude of speed-up (and they depend on a bunch of HW/SW factors
anyway), I'm not going to do another respin. The applying person (most
likely Stephen) is free to fix the numbers when applying if they wish
to do so.
>
> Signed-off-by: Ondrej Mosnacek <omosnace@xxxxxxxxxx>
> ---
>
> v2: corrected time values in commit message
>
> libsepol/include/sepol/policydb/ebitmap.h | 1 +
> libsepol/src/ebitmap.c | 10 ++++++++++
> 2 files changed, 11 insertions(+)
>
> diff --git a/libsepol/include/sepol/policydb/ebitmap.h b/libsepol/include/sepol/policydb/ebitmap.h
> index e62df01c..53fafdaa 100644
> --- a/libsepol/include/sepol/policydb/ebitmap.h
> +++ b/libsepol/include/sepol/policydb/ebitmap.h
> @@ -37,6 +37,7 @@ typedef struct ebitmap_node {
> typedef struct ebitmap {
> ebitmap_node_t *node; /* first node in the bitmap */
> uint32_t highbit; /* highest position in the total bitmap */
> + unsigned int cardinality; /* cached value of cardinality */
> } ebitmap_t;
>
> #define ebitmap_length(e) ((e)->highbit)
> diff --git a/libsepol/src/ebitmap.c b/libsepol/src/ebitmap.c
> index 6c9951b7..d23444ce 100644
> --- a/libsepol/src/ebitmap.c
> +++ b/libsepol/src/ebitmap.c
> @@ -67,6 +67,7 @@ int ebitmap_union(ebitmap_t * dst, const ebitmap_t * e1)
> ebitmap_destroy(dst);
> dst->node = tmp.node;
> dst->highbit = tmp.highbit;
> + dst->cardinality = 0;
>
> return 0;
> }
> @@ -128,9 +129,14 @@ int ebitmap_andnot(ebitmap_t *dst, ebitmap_t *e1, ebitmap_t *e2, unsigned int ma
> unsigned int ebitmap_cardinality(ebitmap_t *e1)
> {
> unsigned int i, count = 0;
> +
> + if (e1->cardinality || e1->highbit == 0)
> + return e1->cardinality;
> +
> for (i=ebitmap_startbit(e1); i < ebitmap_length(e1); i++)
> if (ebitmap_get_bit(e1, i))
> count++;
> + e1->cardinality = count;
> return count;
> }
>
> @@ -194,6 +200,7 @@ int ebitmap_cpy(ebitmap_t * dst, const ebitmap_t * src)
> }
>
> dst->highbit = src->highbit;
> + dst->cardinality = src->cardinality;
> return 0;
> }
>
> @@ -309,6 +316,7 @@ int ebitmap_set_bit(ebitmap_t * e, unsigned int bit, int value)
> free(n);
> }
> }
> + e->cardinality = 0; /* invalidate cached cardinality */
> return 0;
> }
> prev = n;
> @@ -339,6 +347,7 @@ int ebitmap_set_bit(ebitmap_t * e, unsigned int bit, int value)
> e->node = new;
> }
>
> + e->cardinality = 0; /* invalidate cached cardinality */
> return 0;
> }
>
> @@ -358,6 +367,7 @@ void ebitmap_destroy(ebitmap_t * e)
>
> e->highbit = 0;
> e->node = 0;
> + e->cardinality = 0;
> return;
> }
>
> --
> 2.24.1
>
--
Ondrej Mosnacek <omosnace at redhat dot com>
Software Engineer, Security Technologies
Red Hat, Inc.
