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Date: Tue, 25 Mar 2008 19:14:51 -0400 From: Chris Snook <csnook@...hat.com> To: "J.C. Pizarro" <jcpiza@...il.com> CC: LKML <linux-kernel@...r.kernel.org> Subject: Re: Why /proc/cpuinfo doesn't print L1,L2,L3 caches? J.C. Pizarro wrote: > On 2008/3/25, Chris Snook <csnook@...hat.com> wrote: >> J.C. Pizarro wrote: >> > On 2008/3/25, Chris Snook <csnook@...hat.com> wrote: >> >> J.C. Pizarro wrote: >> >> > $ cat /proc/cpuinfo >> >> > processor : 0 >> >> > vendor_id : AuthenticAMD >> >> > cpu family : 15 >> >> > model : 47 >> >> > model name : AMD Athlon(tm) 64 Processor 3200+ >> >> > ... >> >> > cache size : 512 KB >> >> > ... >> >> > >> >> > The cache size is currently misinformed. It's not the real size because >> >> > it's 64+64+512 KiB = 640 KiB, not 512 KB. >> >> > >> >> > How can i know what hw-caches use the processors? >> >> > The current kernel doesn't know well what hw-caches uses. >> >> > >> >> > The good proposal is by example (the data below are not real): >> >> > * In old AMD Athlon64: >> >> > >> >> > cache L1 : 64 KiB I + 64 KiB D, 64 B line, direct way, ... >> >> > cache L2 : 512 KiB I+D-shared, exclusive, 128 associative way, ... >> >> > cache L3 : none >> >> > >> >> > * In Intel Core Duo: >> >> > processor : 0 >> >> > cache L1 : 32 KiB I + 32 KiB D, 64 B line, direct way, ... >> >> > cache L2 : 2048 KiB Cores-shared, inclusive, 128 associative way, ... >> >> > cache L3 : none >> >> > >> >> > processor : 1 >> >> > cache L1 : 32 KiB I + 32 KiB D, 64 B line, direct way, ... >> >> > cache L2 : 2048 KiB cores-shared, inclusive, 128 associative way, ... >> >> > cache L3 : none >> >> > >> >> > * In Quad: >> >> > processor : 0 >> >> > cache L1 : 32 KiB I + 32 KiB D, 64 B line, direct way, ... >> >> > cache L2 : 2048+2048 KiB pair-cores-shared, inclusive, 128 >> >> > associative way, ... >> >> > cache L3 : none >> >> > ... >> >> > processor : 3 >> >> > cache L1 : 32 KiB I + 32 KiB D, 64 B line, direct way, ... >> >> > cache L2 : 2048+2048 KiB pair-cores-shared, inclusive, 128 >> >> > associative way, ... >> >> > cache L3 : none >> >> > >> >> > It above is an example, put your symbols to /proc/cpuinfo in a >> >> > convenient manner. >> >> > >> >> > Good bye ;) >> >> >> >> >> >> I think you want this: >> >> >> >> /sys/devices/system/cpu/cpu0/cache >> > >> > Thanks, but there is not easier manner to print the properties of hw-caches >> > unless printing recursively this tree /sys/devices/system/cpu/cpu[0-9]+/cache/ >> > that they are only numbers without symbolic fields. >> >> >> Then use dmidecode. It's all in one place, and everyone expects it to be far >> too long to read at a glance. >> >> >> > There is not manner to know the speed (in MHz) of the L1, L2 and L3 caches. >> > >> >> /proc/cpuinfo is intended to give a general summary of certain properties of the >> >> processor that tend to be particularly interesting, and present them all in one >> >> place. It is not intended to expose everything the kernel knows about every >> >> processor on the system. >> > >> > /proc/cpuinfo doesn't give a general summary because it gives superfluous info. >> > >> > I think that it's better to refactorize /proc/cpuinfo still more. >> > >> > ( >> > ... fields common to all present processors known by the kernel .... >> > [ to warn if the values are differents between cores ] >> > ) >> > ( >> > ... specific fields for each processor ... by example: >> > >> > processor : 0 >> > cpu MHz : 2000.000 # normal clocked >> > bogomips : 4010.63 >> > processor : 1 >> > cpu MHz : 500.000 # underclocked for energy saving ... >> > bogomips : 1003.20 >> > >> > ) >> > >> > I think that all the cores are equals in almost non-weird systems. >> > With this scheme, the cpuinfo's reports will be smaller than before, >> > and non-superfluous. >> >> >> It's precisely that sort of weirdness we want to be able to catch at a glance. >> These days, there is no possible way to make /proc/cpuinfo satisfy everyone and >> still be compact. That's why we mostly leave it alone and put all the fun stuff >> in /sys, which is much better suited to the ever-increasing complexity of modern >> hardware. >> >> If we refactor /proc/cpuinfo, it will break all sorts of things that use that >> information to get an idea of what the system is running on. All of the info is >> there in /sys now anyway, so if you want a different format, write your own >> userspace tool to scrape it together. There's absolutely no need to implement >> this purely cosmetic data formatting in the kernel. >> >> >> -- Chris > > Well, i understand as if this cosmetic data formatting can break the grep of > some applications. > > But if the modern PC has 6 or 8 cores then it prints an equivalent to > x6 or x8 common pages in a small xterm console of 80x25 although > the panoramic TFT is bigger as 23' 1900x1200 pixels. > > Tomorrow, 32 cores, it prints x32 instead of x8. > Soon, it will need cosmetic data formatting. > > Hahahaha ;) All the more reason to use an interface that allows you to pick and choose the data you want, like /sys. -- Chris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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