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How much RAM for Ryzen3950x and tmpfs?
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C1REX
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PostPosted: Mon Feb 10, 2020 9:26 am    Post subject: How much RAM for Ryzen3950x and tmpfs? Reply with quote

Hi,

I'm planning to build a PC and to come back to Gentoo after few years break.

If building my system with 32thread processor how much RAM would I need to would be able to emerge every package in RAM?

I've heard Chromium with high treaded processors take insane amount of ram to compile.
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liree
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PostPosted: Mon Feb 10, 2020 7:24 pm    Post subject: Reply with quote

I am doing the chromium compile with 32GiB.

If I remember correctly the memory usage while compiling chromium exceeds 16GiB. (maybe around 22)

At that price point for the processor 32 of RAM should not hurt. Therefore I say, 32GiB is sufficient. (However, I haven't compiled every available package)
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Ant P.
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PostPosted: Mon Feb 10, 2020 7:38 pm    Post subject: Reply with quote

Chromium needs about 2GB per make job, it gets worse at the end due to a LTO step but by then most of the compilation jobs have finished.

Installing sys-block/zram-init might help. If your RAM fills up it'll attempt to compress the tmpfs which should work well as it's mostly source code.
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jfp
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PostPosted: Mon Feb 10, 2020 7:43 pm    Post subject: Reply with quote

I have an AMD 3700x (8 cores / 16 threads) with 64GB of memory.

At one point I was trying to stress out the machine and I think I set my MAKEOPTS to -j32 just to see if I could use all of the 64GB and the highest memory utilization I saw in htop was (iirc) ~45GB. That would of course be when chromium or qtwebengine was compiling. Now I just set it to -j15 and it is plenty fast.

The vast majority of the time memory utilization is quite low.

Given that, I have /var/tmp/portage as a 16GB tmpfs and have never seen the swap used at all.
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NeddySeagoon
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PostPosted: Mon Feb 10, 2020 11:42 pm    Post subject: Reply with quote

C1REX,

On a 96 core (one thread per core) system, I have not been able to get more than 72G RAM used. It has 128G fitted.
That was running MAKEOPTS="-j100" emerge --jobs=6 and it happened to build firefox, libreoffice and another biggie concurrently.
The load average was just over 300.

Look at the max RAM the motherboard will take. Provision half the max RAM in such a way as you can add the other half later.
You will add it one day and there is no point in throwing away the original RAM to do it.
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dimko
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PostPosted: Wed Feb 12, 2020 7:21 pm    Post subject: have 64gigs, feel like i wasted money Reply with quote

had 32 gigs with ryzen 5 for god knows how many years.

Not once while compiling something I have seen more than 20 gigs used. Add 5-6 for Xorg, firefox and chrome thunderbird etc - never run out of memory. Never had swap partition for last 7-8 years or so.
ram consumption did not change with Ryzen 9. Unless I compiled FF + Chrome and Libre Office same time with --jobs=6 and with make -j32. And even then it did not go over 32 gigs.
So you probably wont need more than 32 gigs.
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NeddySeagoon
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PostPosted: Wed Feb 12, 2020 7:32 pm    Post subject: Reply with quote

dimko

dimko wrote:
So you probably wont need more than 32 gigs.

I would add "to start with"

History shows that 640k RAM really isn't enough for anyone.
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dimko
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PostPosted: Wed Feb 12, 2020 7:38 pm    Post subject: Reply with quote

NeddySeagoon wrote:
dimko


I would add "to start with"


I got 64 gigs, i feel sorry i bought it.(upgraded, had 2 modules 16gigs, now have 4)
I can't imagine where i would need more. Feel free to answer my question here: https://forums.gentoo.org/viewtopic-t-1108282.html

There is such thing as too much hardware...
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