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authorCarsten Haitzler (Rasterman) <raster@rasterman.com>2016-11-06 12:30:13 +0900
committerCarsten Haitzler (Rasterman) <raster@rasterman.com>2016-11-06 13:13:10 +0900
commitf18d9d7237b6415735d0faae27ab817732047265 (patch)
tree75394f08b603f66e4dfd06b21d6435876499e4ea /src/lib/evas/include/evas_private.h
parent45771d47abb481f3bb84480381b5c9152f20dc9e (diff)
remove memcmp calls for better performance where size is known
so i have been doing some profiling on my rpi3 ... and it seems memcmp() is like the number one top used function - especially running e in wayland compositor mode. it uses accoring to perf top about 9-15% of samples (samples are not adding up to 100%). no - i cant seem to get a call graph because all that happens is the whole kernel locks up solid if i try, so i can only get the leaf node call stats. what function was currently active at the sample time. memcmp is the biggest by far. 2-3 times anything else. 13.47% libarmmem.so [.] memcmp 6.43% libevas.so.1.18.99 [.] _evas_render_phase1_object_pro 4.74% libevas.so.1.18.99 [.] evas_render_updates_internal.c 2.84% libeo.so.1.18.99 [.] _eo_obj_pointer_get 2.49% libevas.so.1.18.99 [.] evas_render_updates_internal_l 2.03% libpthread-2.24.so [.] pthread_getspecific 1.61% libeo.so.1.18.99 [.] efl_data_scope_get 1.60% libevas.so.1.18.99 [.] _evas_event_object_list_raw_in 1.54% libevas.so.1.18.99 [.] evas_object_smart_changed_get 1.32% libgcc_s.so.1 [.] __udivsi3 1.21% libevas.so.1.18.99 [.] evas_object_is_active 1.14% libc-2.24.so [.] malloc 0.96% libevas.so.1.18.99 [.] evas_render_mapped 0.85% libeo.so.1.18.99 [.] efl_isa yeah. it's perf. it's sampling so not 100% accurate, but close to "good enough" for the bigger stuff. so interestingly memcmp() is actually in a special library/module (libarmmem.so) and is a REAL function call. so doing memcmp's for small bits of memory ESPECIALLY when we know their size in advance is not great. i am not sure our own use of memcmp() is the actual culprit because even with this patch memcmp still is right up there. we use it for stringshare which is harder to remove as stringshare has variable sized memory blobs to compare. but the point remains - memcmp() is an ACTUAL function call. even on x86 (i checked the assembly). and replacing it with a static inline custom comparer is better. in fact i did that and benchmarked it as a sample case for eina_tiler which has 4 ints (16 bytes) to compare every time. i also compiled to assembly on x86 to inspect and make sure things made sense. the text color compare was just comparing 4 bytes as a color (an int worth) which was silly to use memcmp on as it could just cast to an int and do a == b. the map was a little more evil as it was 2 ptrs plus 2 bitfields, but the way bitfields work means i can assume the last byte is both bitfields combined. i can be a little more evil for the rect tests as 4 ints compared is the same as comparing 2 long longs (64bit types). yes. don't get pedantic. all platforms efl works on work this way and this is a base assumption in efl and it's true everywhere worth talking about. yes - i tried __int128 too. it was not faster on x86 anyway and can't compile on armv7. in my speed tests on x86-64, comparing 2 rects by casting to a struct of 2 long long's and comparing just those is 70% faster than comapring 4 ints. and the 2 long longs is 360% faster than a memcmp. on arm (my rpi3) the long long is 12% faster than the 4 ints, and it is 226% faster than a memcmp(). it'd be best if we didnt even have to compare at all, but with these algorithms we do, so doing it faster is better. we probably should nuke all the memcmp's we have that are not of large bits of memory or variable sized bits of memory. i set breakpoints for memcmp and found at least a chunk in efl. but also it seems the vc4 driver was also doing it too. i have no idea how much memory it was doing this to and it may ultimately be the biggest culprit here, BUT we may as well reduce our overhead since i've found this anyway. less "false positives" when hunting problems. why am i doing this? i'm setting framerate hiccups. eg like we drop 3, 5 or 10 frames, then drop another bunch, then go back to smooth, then this hiccup again. finding out WHAT is causing that hiccup is hard. i can only SEE the hiccups on my rpi3 - not on x86. i am not so sure it's cpufreq bouncing about as i've locked cpu to 600mhz and it still happens. it's something else. maybe something we are polling? maybe it's something in our drm/kms backend? maybe its in the vc4 drivers or kernel parts? i have no idea. trying to hunt this is hard, but this is important as this is something that possibly is affecting everyone but other hw is fast enough to hide it... in the meantime find and optimize what i find along the way. @optimize
Diffstat (limited to 'src/lib/evas/include/evas_private.h')
-rw-r--r--src/lib/evas/include/evas_private.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/src/lib/evas/include/evas_private.h b/src/lib/evas/include/evas_private.h
index 6b0ff6862c..5271ac5805 100644
--- a/src/lib/evas/include/evas_private.h
+++ b/src/lib/evas/include/evas_private.h
@@ -1002,6 +1002,8 @@ struct _Evas_Object_Proxy_Data
1002 1002
1003struct _Evas_Object_Map_Data 1003struct _Evas_Object_Map_Data
1004{ 1004{
1005 // WARNING - you cannot change the below cur/prev layout, content or size
1006 // unless you also update evas_object_main.c _map_same() func
1005 struct { 1007 struct {
1006 Evas_Map *map; 1008 Evas_Map *map;
1007 Evas_Object *map_parent; 1009 Evas_Object *map_parent;