David Hildenbrand <david@xxxxxxxxxx> writes: > On 15.08.23 19:10, Stefan Roesch wrote: >> David Hildenbrand <david@xxxxxxxxxx> writes: >> >>> Sorry for the late reply, Gmail once again decided to classify your mails as >>> spam (for whatever reason). >>> >>> On 11.08.23 18:28, Stefan Roesch wrote: >>>> With madvise and prctl KSM can be enabled for different VMA's. Once it >>>> is enabled we can query how effective KSM is overall. However we cannot >>>> easily query if an individual VMA benefits from KSM. >>>> This commit adds a KSM section to the /prod/<pid>/smaps file. It reports >>>> how many of the pages are KSM pages. >>>> Here is a typical output: >>>> 7f420a000000-7f421a000000 rw-p 00000000 00:00 0 >>>> Size: 262144 kB >>>> KernelPageSize: 4 kB >>>> MMUPageSize: 4 kB >>>> Rss: 51212 kB >>>> Pss: 8276 kB >>>> Shared_Clean: 172 kB >>>> Shared_Dirty: 42996 kB >>>> Private_Clean: 196 kB >>>> Private_Dirty: 7848 kB >>>> Referenced: 15388 kB >>>> Anonymous: 51212 kB >>>> KSM: 41376 kB >>>> LazyFree: 0 kB >>>> AnonHugePages: 0 kB >>>> ShmemPmdMapped: 0 kB >>>> FilePmdMapped: 0 kB >>>> Shared_Hugetlb: 0 kB >>>> Private_Hugetlb: 0 kB >>>> Swap: 202016 kB >>>> SwapPss: 3882 kB >>>> Locked: 0 kB >>>> THPeligible: 0 >>>> ProtectionKey: 0 >>>> ksm_state: 0 >>>> ksm_skip_base: 0 >>>> ksm_skip_count: 0 >>>> VmFlags: rd wr mr mw me nr mg anon >>>> This information also helps with the following workflow: >>>> - First enable KSM for all the VMA's of a process with prctl. >>>> - Then analyze with the above smaps report which VMA's benefit the most >>>> - Change the application (if possible) to add the corresponding madvise >>>> calls for the VMA's that benefit the most >>>> Signed-off-by: Stefan Roesch <shr@xxxxxxxxxxxx> >>>> --- >>>> Documentation/filesystems/proc.rst | 3 +++ >>>> fs/proc/task_mmu.c | 5 +++++ >>>> 2 files changed, 8 insertions(+) >>>> diff --git a/Documentation/filesystems/proc.rst >>>> b/Documentation/filesystems/proc.rst >>>> index 7897a7dafcbc..4ef3c0bbf16a 100644 >>>> --- a/Documentation/filesystems/proc.rst >>>> +++ b/Documentation/filesystems/proc.rst >>>> @@ -461,6 +461,7 @@ Memory Area, or VMA) there is a series of lines such as the following:: >>>> Private_Dirty: 0 kB >>>> Referenced: 892 kB >>>> Anonymous: 0 kB >>>> + KSM: 0 kB >>>> LazyFree: 0 kB >>>> AnonHugePages: 0 kB >>>> ShmemPmdMapped: 0 kB >>>> @@ -501,6 +502,8 @@ accessed. >>>> a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE >>>> and a page is modified, the file page is replaced by a private anonymous copy. >>>> +"KSM" shows the amount of anonymous memory that has been de-duplicated. >>> >>> >>> How do we want to treat memory that has been deduplicated into the shared >>> zeropage? >>> >>> It would also match this description. >>> >>> See in mm-stable: >>> >>> commit 30ff6ed9a65c7e73545319fc15f7bcf9c52457eb >>> Author: xu xin <xu.xin16@xxxxxxxxxx> >>> Date: Tue Jun 13 11:09:28 2023 +0800 >>> >>> ksm: support unsharing KSM-placed zero pages >>> >>> Patch series "ksm: support tracking KSM-placed zero-pages", v10. >> I see two approaches how to deal with zero page: >> - If zero page is not enabled, it works as is >> - If enabled >> - Document that zero page is accounted for the current vma or >> - Pass in the pte from smaps_pte_entry() to smaps_account() so we can >> determine if this is a zero page. > > That's probably the right thing to do: make the stat return the same value > independent of the usage of the shared zeropage. > I'll update the documentation accordingly. >> I'm not sure what to do about smaps_pmd_entry in that case. We >> probably don't care about compund pages. > > No, KSM only places the shared zeropage for PTEs, no need to handle PMDs.
