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Date: Mon, 3 Mar 2014 07:39:28 +0000 From: Sudeep Holla <sudeep.holla@....com> To: Greg Kroah-Hartman <gregkh@...uxfoundation.org> Cc: linux-kernel@...r.kernel.org, Rob Herring <robh@...nel.org>, linux-doc@...r.kernel.org Subject: Re: [PATCH RFC/RFT v3 2/9] drivers: base: support cpu cache information interface to userspace via sysfs Hi Greg, On Sat, Mar 1, 2014 at 12:42 AM, Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote: > On Wed, Feb 19, 2014 at 04:06:09PM +0000, Sudeep Holla wrote: >> From: Sudeep Holla <sudeep.holla@....com> >> >> This patch adds initial support for providing processor cache information >> to userspace through sysfs interface. This is based on already existing >> implementations(x86, ia64, s390 and powerpc) and hence the interface is >> intended to be fully compatible. >> >> The main purpose of this generic support is to avoid further code >> duplication to support new architectures and also to unify all the existing >> different implementations. >> >> This implementation maintains the hierarchy of cache objects which reflects >> the system's cache topology. Cache devices are instantiated as needed as >> CPUs come online. The cache information is replicated per-cpu even if they are >> shared. A per-cpu array of cache information maintained is used mainly for >> sysfs-related book keeping. >> >> It also implements the shared_cpu_map attribute, which is essential for >> enabling both kernel and user-space to discover the system's overall cache >> topology. >> >> This patch also add the missing ABI documentation for the cacheinfo sysfs >> interface already, which is well defined and widely used. >> >> Signed-off-by: Sudeep Holla <sudeep.holla@....com> >> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org> >> Cc: Rob Herring <robh@...nel.org> >> Cc: linux-doc@...r.kernel.org >> --- >> Documentation/ABI/testing/sysfs-devices-system-cpu | 40 ++ >> drivers/base/Makefile | 2 +- >> drivers/base/cacheinfo.c | 484 +++++++++++++++++++++ >> include/linux/cacheinfo.h | 55 +++ >> 4 files changed, 580 insertions(+), 1 deletion(-) >> create mode 100644 drivers/base/cacheinfo.c >> create mode 100644 include/linux/cacheinfo.h >> >> diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu >> index d5a0d33..dabe03e 100644 >> --- a/Documentation/ABI/testing/sysfs-devices-system-cpu >> +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu >> @@ -224,3 +224,43 @@ Description: Parameters for the Intel P-state driver >> frequency range. >> >> More details can be found in Documentation/cpu-freq/intel-pstate.txt >> + >> +What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below> >> +Date: February 2014 >> +Contact: Linux kernel mailing list <linux-kernel@...r.kernel.org> > > No, your name goes here, you don't get to run away from this new code :) > No problem, I can add my name and I am happy to do that. I am only adding missing documentation to already existing interface as I have mentioned in the patch description. I didn't want to take that credit :), but am OK if that's acceptable. >> +Description: Parameters for the CPU cache attributes >> + >> + attributes: >> + - writethrough: data is written to both the cache line >> + and to the block in the lower-level memory >> + - writeback: data is written only to the cache line and >> + the modified cache line is written to main >> + memory only when it is replaced >> + - writeallocate: allocate a memory location to a cache line >> + on a cache miss because of a write >> + - readallocate: allocate a memory location to a cache line >> + on a cache miss because of a read >> + >> + coherency_line_size: the minimum amount of data that gets transferred >> + >> + level: the cache hierarcy in the multi-level cache configuration >> + >> + number_of_sets: total number of sets in the cache, a set is a >> + collection of cache lines with the same cache index >> + >> + physical_line_partition: number of physical cache line per cache tag >> + >> + shared_cpu_list: the list of cpus sharing the cache >> + >> + shared_cpu_map: logical cpu mask containing the list of cpus sharing >> + the cache >> + >> + size: the total cache size in kB >> + >> + type: >> + - instruction: cache that only holds instructions >> + - data: cache that only caches data >> + - unified: cache that holds both data and instructions >> + >> + ways_of_associativity: degree of freedom in placing a particular block >> + of memory in the cache > > With this patch, does this all work for x86, or does it need more glue > logic? No, the core code is mainly based on existing x86 implementation. There should be no extra glue logic required. I have not yet tested on x86, but will do that before the first non-RFC post if the overall approach is now acceptable. But I still need help in testing on AMD, ia64 and ppc. Regards, Sudeep -- 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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