On 3/19/21 6:28 AM, Faiyaz Mohammed wrote: > Hi, > > Sorry for late response! > > On 3/2/2021 6:41 PM, Greg Kroah-Hartman wrote: >> On Tue, Mar 02, 2021 at 01:59:46PM +0100, Vlastimil Babka wrote: >>> On 2/17/21 7:31 AM, Faiyaz Mohammed wrote: >>>> Reading the sys slab alloc_calls, free_calls returns the available object >>>> owners, but the size of this file is limited to PAGE_SIZE >>>> because of the limitation of sysfs attributes, it is returning the >>>> partial owner info, which is not sufficient to debug/account the slab >>>> memory and alloc_calls output is not matching with /proc/slabinfo. >>>> >>>> To remove the PAGE_SIZE limitation converted the sys slab >>>> alloc_calls, free_calls to bin attribut >>>> >>>> Signed-off-by: Faiyaz Mohammed <faiyazm@xxxxxxxxxxxxxx> >>> >>> After discussing this with Greg and PeterZ, sysfs should be one value per file, >>> and is just not proper API for this kind of info. We should reimplement at least >>> these clearly debugging "attributes" in debugfs, where they belong, instead of >>> trying to hack around the limitation in sysfs. >> >> sysfs is _REQUIRED_ to be "one value per file", any kernel code that >> abuses this needs to be fixed up. >> >> Why are these slab files in sysfs at all anyway? They all feel like >> debugging stuff to me, why not move everything to debugfs? Would make >> for a lot less code overall. >> > Yes, we can move the /sys/kernel/slab/kmemcache/alloc_calls and > /sys/kernel/slab/kmemcache/free_calls implementation to debugfs but is > it okay to move only alloc_calls and free_calls? or we have to move > whole sysfs interface to debugfs?. I don't think we need to move everything, just files where it makes sense. > If we are moving only alloc_calls/free_calls interface to debugfs then I > think we can add all slab objects data into single file. > > For example: /sys/kernel/debugfs/slab/alloc_calls, which will print all > slab objects data. > > Example Output: alloc_list: call_site=__request_region+0xb4/0x2f0 > count=228 object_size=128 slab_size=640 slab_name=kmalloc-128 I wouldn't do this, as processing all caches will have a large overhead and then somebody interested in single cache would throw most of the info away. > or > > We can have just like current sysfs interface, have separate > alloc_calls/free_calls traces per kmem cache. > > Which one would be better?. > >> > > Thanks and regards, > Mohammed Faiyaz >
