On Jun 23 15:39, Marco Atzeri wrote: > Hi Corinna, > > for a porting of a math lib to cygwin we are trying to obtain > the same information of > > sysconf(_SC_LEVEL1_DCACHE_SIZE) > sysconf(_SC_LEVEL2_CACHE_SIZE) > sysconf(_SC_LEVEL3_CACHE_SIZE) > sysconf(_SC_LEVEL4_CACHE_SIZE) > > but of course none of them is implemented in cygwin. > > The /proc/cpuinfo contains : > ------------------------------------------------------------------ > [...] > cache size : 256 KB > [...] > ------------------------------------------------------------------ > > Looking on the code it seems that for > maxe >= 0x80000006 > > cache_size reported on cpuinfo is calculated using L1 > and immediately after overwritten with L2 value.
This seems to be right, at least partially. Linux /proc/cpuinfo appears to report only the size of the outmost available cache. So if you have L1 and L2 caches, Linux reports the L2 cache size. The problem is that the L2 cache isn't the outmost available cache anymore these days. On my CPU Cygwin reports 256K, which is the size of the per-core L2 caches. However, the shared L3 cache has a size of 15Megs, and that's what Linux reports: $ grep 'cache size' /proc/cpuinfo | head -1 cache size : 15360 KB Cygwin is lacking the code to fetch L3 caches and afaics, it's not overly simple. At least calling cpuid as for L1 and L2 caches is not sufficient, apparently. > Should be possible to have both info available ? > Any idea how to obtain the other cache infos ? Not completely. You have to use different cpuid codes for AMD and Intel CPUs, and you have to call cpuid multiple times to get the full info for all L3 caches of the system's CPUs, but I'm fuzzy on the details. Patches are certainly welcome. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
pgp3CpNagbd52.pgp
Description: PGP signature
