-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Friday, 2017-12-01 at 12:06 -0800, L A Walsh wrote: :-)))
Wol's lists wrote:
Try running a *vanilla* early 2.4 series kernel with swap == ram. As soon as the system even *touches* swap IT WILL CRASH.
--- We are in the 4.x series, what does an early bug have to do with this issue?
Because we were talking of the old "rule" of swap must be twice the ram. I say there has never been such a rule in Linux, and also that in Windows 3 the rule was a maximum twice as ram, the rest was ignored.
In Linux I have run machines with about 30 times SWAP/RAM ratio. It worked fine - albeit slowly, of course. Yes, that amount of swap was needed, there was a memory hole in YaST that ate ram when updating.
In this desktop machine the ratio is 3.
The rule is "use as much as you like", agreed. But in order to work *efficiently*, the traditional Unix swap algorithm *needs* twice ram. It's a fundamental quirk of how it works.
---- Linux's virtual memory algorithms are not those used in Unix. I don't think you can find a "traditional Unix" system from anyone anymore. If you need kernel core dumps, then you need as much space in swap as you have in memory (for the core image). If you aren't doing kernel development and you have enough memory for your needs, swap doesn't get touched. An SSD may be faster than a hard disk, but is many factors of 10 slower than RAM. I.e. memory read/write speeds are in GB/s, while small random read/writes to an SSD will be 4 to 16 times SLOWER than listed sequential testing (comparing 4K R/W to sequential R/W on http://ssd.userbenchmark.com/). This works out to <100MB/s for an SSD swap. Translation: SSD's for swap/page are about 500-1000 times slower than using RAM.
Of course :-) But it is much faster than rotating rust. I did that, change swap from rust to ssd, and the improvement is large, even though limited to 3 GB/s bus. In my opinion, the speed comes not only from the faster speed, but from not having to seek, and thus fragmentation is not an issue on SSD. I noticed that Leap is noticiably slower than 13.1 regarding swap. So much so that I had to look for a solution, which was an SSD (more RAM was out of the question). - -- Cheers, Carlos E. R. (from openSUSE 42.2 x86_64 "Malachite" at Telcontar) -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAloh5DkACgkQtTMYHG2NR9UEwQCghA3xTC4girD5TrEAgmcLbiR9 F6YAn2l1UJ81slSS7/uOA0RuCHCRqnre =j3LY -----END PGP SIGNATURE----- -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org