On Fri, Feb 14, 2020 at 8:51 PM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote: > On Fri, Feb 14, 2020 at 6:37 PM Stephen Smalley <sds@xxxxxxxxxxxxx> 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@xxxxxxxxxx> > > > > 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... BTW, in case anyone is wondering how I'm getting these numbers/facts - I use Callgrind [1] to profile a program's run and then analyze it with KCachegrind [2]. It is a surprisingly nice and easy to use GUI for analyzing where the program spends most of its time. Collecting the profile data is as simple as: LD_BIND_NOW=1 valgrind --tool=callgrind <your_command> <args>... (The LD_BIND_NOW=1 is to prevent the dynamic linker's lazy binding from messing with the results.) Then you can just open the generated "callgrind.out.<pid>" file with KCachegrind and click around... Note that to see the function names, you need to compile the program with -g (but you should keep -O2 et al. to get the same optimized code as an actual build). Alternatively, Callgrind will also auto-detect and use debug symbols provided by distributions in their -debug/-debuginfo packages. Maybe this is common knowledge for most, but perhaps someone here will be one of today's lucky 10000 :) [3] [1] https://valgrind.org/docs/manual/cl-manual.html [2] https://kcachegrind.github.io/html/Home.html [3] https://xkcd.com/1053/ -- Ondrej Mosnacek <omosnace at redhat dot com> Software Engineer, Security Technologies Red Hat, Inc.
