Because if there are 4 cores doing heavy CPU lifting of 4 threads, when one is finished, you then waste time loading up the next thread because it's reading from the disk. If you have it already done with I/O it will be ready and less time is wasted. Calvin On Apr 1, 2012 9:09 AM, "Baho Utot" <baho-utot@columbus.rr.com> wrote:
On 04/01/2012 08:37 AM, Calvin Morrison wrote:
Often higher cores benefit high I/O applications. If gcc is bottlenecking at reading and writing, sometimes more threads will help.
How does that help?
Sounds backwards to me
On Apr 1, 2012 7:49 AM, "Vitor Garcia"<vitorlopesgarcia@**gmail.com<vitorlopesgarcia@gmail.com>>
wrote:
On Sun, 01 Apr 2012 13:37:27 +0200
Florian Pritz<bluewind@xinu.at> wrote:
Simple tests (building readline because it's small) with -j4 and -j8
on my i7-920 show that -j8 is around 20% faster than -j4. IIRC wikipedia states that HT core can increase performance by up to 30%.
This is nice to know. I work with mechanichal engineering simulations and we have noted that using more threads then avaiable processors (we have a 2 x 6 cores processors that has HT, so it looks like a 24 cores server) increases the calculation time on the softwares we have. I assumed that the same would apply to any intensive task, and we have even disabled HT on the BIOS. Perhaps I'll enable it again.