how to play games and emerge?

[dimko]

I have 8 core 4 GHZ CPU.
I play games, using steam.
I set emerge to use 4 cores and have highest nice value of 20.
Game FPS drops a lot.(any game)
even though game has lowest nice value.(steam as parent process)
why is this happening?

I checked with htop, emerge uses 4 cores and has blue color, so my settings for emerge and steam are correct.
What can I do to avoid low FPS?(and run oth games and emerge at same time)

my sys:
780Ti binary nvidia, 4ghz vishera from AMD(8 core). 32 Gb of ram(1600).

Thank you in advance!
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Just a user.

[bstaletic]

I never played with nice, so can't truly help, but why don't you just postpone emerge and let it work while you're not using you pc?

[dimko]

[NeddySeagoon]

dimko,

Three things come to mind,

IO bandwidth
Memory bandwidth
Cache thrashing

nice sets how hard processes fight over the CPU - it says nothing about disc access.
Games and emerge both need disk access, if you don't have SSD, then you have the head movement latency an the drive seeks between the game area and the areas emerge wants.

The game and emerge need to share access to main memory. If emerge is using it, the game cannot.

Cache thrashing in an interesting one. Your CPU has a small amount of memory that runs at the full CPU core speed. Its 100 or so times faster than main memory, when you consider the main memory latency. While you are using 4 cores for a game and 4 cores for emerge, there is no such restriction on the CPU cache RAM. What happens is that one process will push another process out of the cache. This forces the process that was pushed out to fetch thing from much slower main memory, increasing the pressure on the memory bandwidth.
The CPU cache manager keeps the most recently used data in cache.

Its all very well using 4 cores each but how many jobs is emerge allowed to use?
You need to manage the number of running threads.

How do you set emerge to use 4 cores?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[Naib]

The solution I use is cgroups. Games are given exclusive access to a lion share of bandwidth, ram and cpu.
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[dimko]

[dimko]

[Chiitoo]

It's been quite a while since I started using the sys-kernel/ck-sources, and haven't tried any other for a long while so I can't really say for sure it's a huge difference still. I do seem to remember there being quite a change back some years ago at least when I did first try them out.

I can emerge with all my 6 cores while playing, without huge performance drops (more during some builds than during others).

So if you haven't yet, perhaps give the BFS a try. ^^
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Kindest of regardses.

[krinn]

You should also think about core in use.

If 4 cores out of your 8 are busy, and the game try to use one of the 4 busy cores...

Have a look at taskset to handle what cores do what work (as many scheduler are dumb, pushing emerge on 4 latest cores might be enough as many games never need more than 2-3 cores in real).

Or goes with Chiitoo's suggest, while i'm not myself familiar with BFS it might do a better balancing...

[dimko]

[dimko]

[krinn]

then lower it to 2 cores only, as your cpu have only 4 cores (even 8 logical ones are seen)
it's no worst than intel with ht, but alas, it's also not better.

[dimko]

[krinn]

ps: don't forget to look at /proc/cpuinfo and ident each core by its "core id" number, as assigning "core id 0 cpu cores 4" and "core id 0 cpu cores 6" will not assign tasks to two cores, but on the same one.

[dimko]

[dimko]

[Syl20]

[krinn]

[dimko]

Well, for compiling, which, AFAIK, fpu is not needed much, so I did buy my CPU with this in mind. This + gaming are my biggest CPU eaters. I admit, I am a bit AMD CPU fan boy + it costs far less than Intel, most of time I am simply broke. Anyway, games I play should be sorta, kinda, OK with 'dual core'. So I imagine, out of 4 FPU CPU's 2 should be enough for something like sword coast legends.(780 TI nvidia, which is rather not bad card)

for your curiosity, here is proc 0 and proc 7 from /proc:

processor : 0
vendor_id : AuthenticAMD
cpu family : 21
model : 2
model name : AMD FX(tm)-8350 Eight-Core Processor
stepping : 0
microcode : 0x600081c
cpu MHz : 2100.000
cache size : 2048 KB
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
apicid : 16
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold vmmcall bmi1
bugs : fxsave_leak sysret_ss_attrs
bogomips : 8035.86
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro

processor : 7
vendor_id : AuthenticAMD
cpu family : 21
model : 2
model name : AMD FX(tm)-8350 Eight-Core Processor
stepping : 0
microcode : 0x600081c
cpu MHz : 2800.000
cache size : 2048 KB
physical id : 0
siblings : 8
core id : 7
cpu cores : 4
apicid : 23
initial apicid : 7
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm constant_tsc rep_good nopl nonstop_tsc extd_apicid aperfmperf pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 popcnt aes xsave avx f16c lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs xop skinit wdt lwp fma4 tce nodeid_msr tbm topoext perfctr_core perfctr_nb arat cpb hw_pstate npt lbrv svm_lock nrip_save tsc_scale vmcb_clean flushbyasid decodeassists pausefilter pfthreshold vmmcall bmi1
bugs : fxsave_leak sysret_ss_attrs
bogomips : 8035.86
TLB size : 1536 4K pages
clflush size : 64
cache_alignment : 64
address sizes : 48 bits physical, 48 bits virtual
power management: ts ttp tm 100mhzsteps hwpstate cpb eff_freq_ro
_________________
Just a user.

[dimko]

[Naib]

possibly... FPS drop can be caused by anything causing rendering to ... pause. Be it too long to render, IO bound waiting for new info from net (or inputs if bad code) and equally sound...

or the drivers are shocking... and alot of "HD sound" onboard chipsets are ... shocking.
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[Chiitoo]

Hmmm.