x264 on Nehalem - Page 4

Sharktooth · 23rd November 2008, 16:45

it's obvious it cant be equal to physical cores...

Sagekilla · 23rd November 2008, 19:46

If x264 (or any other multithreaded app) can't feed the 4 physical threads, then yes the extra logical thread will come in handy. They're there only to help keep the execution units completely filled up, but x264 shouldn't have a hard time keeping the execution units churning out data.

Sharktooth · 26th November 2008, 15:15

HT is exactly the opposite. it doesnt help the software, but the pipeline.
if there are difficulties to keep the pipeline filled, HT becomes effective, otherwise it doesnt.
and that's not a matter of software but of a series of problems a CPU may have (L1 cache too small, pipeline too long, non optimal instructions/data fetch/prefetch, too frequent cache misses, etc...).

LoRd_MuldeR · 26th November 2008, 15:27

However HT requires at least two threads per CPU core to keep all the ALU's busy.

Hence in order to get the maximum benefit from HT on a Quadcore machine, you need at least eight threads running at a time.

Unless your application is multi-threaded and scales well to a huge number of threads, there's no benefit from HT.

Since x264 scales well with many threads, usually, some benefit from HT can be expected...

23rd November 2008, 16:45	#61 \| Link
Sharktooth Mr. Sandman Join Date: Sep 2003 Location: Haddonfield, IL Posts: 11,768	it's obvious it cant be equal to physical cores... __________________ MPEG-4 ASP Custom Matrices: EQM V1(old), EQM AutoGK Sharpmatrix (aka EQM V2), EQM V3HR (updated 01/10/2004), EQM V3LR, EQM V3ULR (updated 04/02/2005), EQM V3UHR (updated 17/12/2004) and EQM V3EHR (updated 05/10/2004) Info about my ASP matrices. MPEG-4 AVC Custom Matrices: EQM AVC-HR Info about my AVC matrices My x264 builds. Mooo!!!

23rd November 2008, 19:46	#62 \| Link
Sagekilla x264aholic Join Date: Jul 2007 Location: New York Posts: 1,752	If x264 (or any other multithreaded app) can't feed the 4 physical threads, then yes the extra logical thread will come in handy. They're there only to help keep the execution units completely filled up, but x264 shouldn't have a hard time keeping the execution units churning out data. __________________ You can't call your encoding speed slow until you start measuring in seconds per frame.

26th November 2008, 15:15	#63 \| Link
Sharktooth Mr. Sandman Join Date: Sep 2003 Location: Haddonfield, IL Posts: 11,768	HT is exactly the opposite. it doesnt help the software, but the pipeline. if there are difficulties to keep the pipeline filled, HT becomes effective, otherwise it doesnt. and that's not a matter of software but of a series of problems a CPU may have (L1 cache too small, pipeline too long, non optimal instructions/data fetch/prefetch, too frequent cache misses, etc...). __________________ MPEG-4 ASP Custom Matrices: EQM V1(old), EQM AutoGK Sharpmatrix (aka EQM V2), EQM V3HR (updated 01/10/2004), EQM V3LR, EQM V3ULR (updated 04/02/2005), EQM V3UHR (updated 17/12/2004) and EQM V3EHR (updated 05/10/2004) Info about my ASP matrices. MPEG-4 AVC Custom Matrices: EQM AVC-HR Info about my AVC matrices My x264 builds. Mooo!!!

26th November 2008, 15:27	#64 \| Link
LoRd_MuldeR Software Developer Join Date: Jun 2005 Location: Last House on Slunk Street Posts: 13,248	However HT requires at least two threads per CPU core to keep all the ALU's busy. Hence in order to get the maximum benefit from HT on a Quadcore machine, you need at least eight threads running at a time. Unless your application is multi-threaded and scales well to a huge number of threads, there's no benefit from HT. Since x264 scales well with many threads, usually, some benefit from HT can be expected... __________________ Go to https://standforukraine.com/ to find legitimate Ukrainian Charities 🇺🇦✊

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