From: Stephen Smalley <sds@tycho.nsa.gov>
To: Ondrej Mosnacek <omosnace@redhat.com>
Cc: SElinux list <selinux@vger.kernel.org>,
James Carter <jwcart2@tycho.nsa.gov>
Subject: Re: [PATCH userspace v2] libsepol: cache ebitmap cardinality value
Date: Fri, 14 Feb 2020 14:57:02 -0500 [thread overview]
Message-ID: <16a48f3a-886c-dbd7-52dd-a97329fa8cdd@tycho.nsa.gov> (raw)
In-Reply-To: <CAFqZXNtpqOszQ5a2s86TTHtQGK_c+vqmtaRPBv04+vFAqExEmg@mail.gmail.com>
On 2/14/20 2:51 PM, Ondrej Mosnacek wrote:
> On Fri, Feb 14, 2020 at 6:37 PM Stephen Smalley <sds@tycho.nsa.gov> wrote:
>> On 2/13/20 8:39 AM, Ondrej Mosnacek 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).
>>>
>>> Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
>>
>> This seems fine but I was wondering how many of the callers of
>> ebitmap_cardinality() actually need anything more than ebitmap_length()?
>
> The caller that calls it the most (>99%) during a 'semodule -B' is
> __cil_should_expand_attribute(), which logically needs the actual
> cardinality. It might be possible to cache the decision directly in
> 'struct cil_typeattribute', but I don't know the CIL code well enough
> to attempt that...
That's fine - I'm ok with the patch itself. I just happened to notice
that there appear to be quite a few callers elsewhere in libsepol that
only seem to care whether the result is zero or non-zero, which
seemingly would be just as happy using ebitmap_length().
next prev parent reply other threads:[~2020-02-14 19:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 13:39 [PATCH userspace v2] libsepol: cache ebitmap cardinality value Ondrej Mosnacek
2020-02-14 17:38 ` Stephen Smalley
2020-02-14 18:20 ` Stephen Smalley
2020-02-14 19:51 ` Ondrej Mosnacek
2020-02-14 19:57 ` Stephen Smalley [this message]
2020-02-14 20:19 ` Ondrej Mosnacek
2020-02-18 15:22 ` Ondrej Mosnacek
2020-02-18 15:41 ` Stephen Smalley
2020-02-18 16:01 ` Ondrej Mosnacek
2020-02-25 21:24 ` Nicolas Iooss
2020-02-25 21:56 ` William Roberts
2020-02-26 13:23 ` Ondrej Mosnacek
2020-02-26 15:39 ` William Roberts
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