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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/admin-guide/mm/pagemap.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/admin-guide/mm/pagemap.rst')
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diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst new file mode 100644 index 000000000..6e2e416af --- /dev/null +++ b/Documentation/admin-guide/mm/pagemap.rst @@ -0,0 +1,232 @@ +.. _pagemap: + +============================= +Examining Process Page Tables +============================= + +pagemap is a new (as of 2.6.25) set of interfaces in the kernel that allow +userspace programs to examine the page tables and related information by +reading files in ``/proc``. + +There are four components to pagemap: + + * ``/proc/pid/pagemap``. This file lets a userspace process find out which + physical frame each virtual page is mapped to. It contains one 64-bit + value for each virtual page, containing the following data (from + ``fs/proc/task_mmu.c``, above pagemap_read): + + * Bits 0-54 page frame number (PFN) if present + * Bits 0-4 swap type if swapped + * Bits 5-54 swap offset if swapped + * Bit 55 pte is soft-dirty (see + :ref:`Documentation/admin-guide/mm/soft-dirty.rst <soft_dirty>`) + * Bit 56 page exclusively mapped (since 4.2) + * Bit 57 pte is uffd-wp write-protected (since 5.13) (see + :ref:`Documentation/admin-guide/mm/userfaultfd.rst <userfaultfd>`) + * Bits 58-60 zero + * Bit 61 page is file-page or shared-anon (since 3.5) + * Bit 62 page swapped + * Bit 63 page present + + Since Linux 4.0 only users with the CAP_SYS_ADMIN capability can get PFNs. + In 4.0 and 4.1 opens by unprivileged fail with -EPERM. Starting from + 4.2 the PFN field is zeroed if the user does not have CAP_SYS_ADMIN. + Reason: information about PFNs helps in exploiting Rowhammer vulnerability. + + If the page is not present but in swap, then the PFN contains an + encoding of the swap file number and the page's offset into the + swap. Unmapped pages return a null PFN. This allows determining + precisely which pages are mapped (or in swap) and comparing mapped + pages between processes. + + Efficient users of this interface will use ``/proc/pid/maps`` to + determine which areas of memory are actually mapped and llseek to + skip over unmapped regions. + + * ``/proc/kpagecount``. This file contains a 64-bit count of the number of + times each page is mapped, indexed by PFN. + +The page-types tool in the tools/vm directory can be used to query the +number of times a page is mapped. + + * ``/proc/kpageflags``. This file contains a 64-bit set of flags for each + page, indexed by PFN. + + The flags are (from ``fs/proc/page.c``, above kpageflags_read): + + 0. LOCKED + 1. ERROR + 2. REFERENCED + 3. UPTODATE + 4. DIRTY + 5. LRU + 6. ACTIVE + 7. SLAB + 8. WRITEBACK + 9. RECLAIM + 10. BUDDY + 11. MMAP + 12. ANON + 13. SWAPCACHE + 14. SWAPBACKED + 15. COMPOUND_HEAD + 16. COMPOUND_TAIL + 17. HUGE + 18. UNEVICTABLE + 19. HWPOISON + 20. NOPAGE + 21. KSM + 22. THP + 23. OFFLINE + 24. ZERO_PAGE + 25. IDLE + 26. PGTABLE + + * ``/proc/kpagecgroup``. This file contains a 64-bit inode number of the + memory cgroup each page is charged to, indexed by PFN. Only available when + CONFIG_MEMCG is set. + +Short descriptions to the page flags +==================================== + +0 - LOCKED + The page is being locked for exclusive access, e.g. by undergoing read/write + IO. +7 - SLAB + The page is managed by the SLAB/SLOB/SLUB/SLQB kernel memory allocator. + When compound page is used, SLUB/SLQB will only set this flag on the head + page; SLOB will not flag it at all. +10 - BUDDY + A free memory block managed by the buddy system allocator. + The buddy system organizes free memory in blocks of various orders. + An order N block has 2^N physically contiguous pages, with the BUDDY flag + set for and _only_ for the first page. +15 - COMPOUND_HEAD + A compound page with order N consists of 2^N physically contiguous pages. + A compound page with order 2 takes the form of "HTTT", where H donates its + head page and T donates its tail page(s). The major consumers of compound + pages are hugeTLB pages + (:ref:`Documentation/admin-guide/mm/hugetlbpage.rst <hugetlbpage>`), + the SLUB etc. memory allocators and various device drivers. + However in this interface, only huge/giga pages are made visible + to end users. +16 - COMPOUND_TAIL + A compound page tail (see description above). +17 - HUGE + This is an integral part of a HugeTLB page. +19 - HWPOISON + Hardware detected memory corruption on this page: don't touch the data! +20 - NOPAGE + No page frame exists at the requested address. +21 - KSM + Identical memory pages dynamically shared between one or more processes. +22 - THP + Contiguous pages which construct transparent hugepages. +23 - OFFLINE + The page is logically offline. +24 - ZERO_PAGE + Zero page for pfn_zero or huge_zero page. +25 - IDLE + The page has not been accessed since it was marked idle (see + :ref:`Documentation/admin-guide/mm/idle_page_tracking.rst <idle_page_tracking>`). + Note that this flag may be stale in case the page was accessed via + a PTE. To make sure the flag is up-to-date one has to read + ``/sys/kernel/mm/page_idle/bitmap`` first. +26 - PGTABLE + The page is in use as a page table. + +IO related page flags +--------------------- + +1 - ERROR + IO error occurred. +3 - UPTODATE + The page has up-to-date data. + ie. for file backed page: (in-memory data revision >= on-disk one) +4 - DIRTY + The page has been written to, hence contains new data. + i.e. for file backed page: (in-memory data revision > on-disk one) +8 - WRITEBACK + The page is being synced to disk. + +LRU related page flags +---------------------- + +5 - LRU + The page is in one of the LRU lists. +6 - ACTIVE + The page is in the active LRU list. +18 - UNEVICTABLE + The page is in the unevictable (non-)LRU list It is somehow pinned and + not a candidate for LRU page reclaims, e.g. ramfs pages, + shmctl(SHM_LOCK) and mlock() memory segments. +2 - REFERENCED + The page has been referenced since last LRU list enqueue/requeue. +9 - RECLAIM + The page will be reclaimed soon after its pageout IO completed. +11 - MMAP + A memory mapped page. +12 - ANON + A memory mapped page that is not part of a file. +13 - SWAPCACHE + The page is mapped to swap space, i.e. has an associated swap entry. +14 - SWAPBACKED + The page is backed by swap/RAM. + +The page-types tool in the tools/vm directory can be used to query the +above flags. + +Using pagemap to do something useful +==================================== + +The general procedure for using pagemap to find out about a process' memory +usage goes like this: + + 1. Read ``/proc/pid/maps`` to determine which parts of the memory space are + mapped to what. + 2. Select the maps you are interested in -- all of them, or a particular + library, or the stack or the heap, etc. + 3. Open ``/proc/pid/pagemap`` and seek to the pages you would like to examine. + 4. Read a u64 for each page from pagemap. + 5. Open ``/proc/kpagecount`` and/or ``/proc/kpageflags``. For each PFN you + just read, seek to that entry in the file, and read the data you want. + +For example, to find the "unique set size" (USS), which is the amount of +memory that a process is using that is not shared with any other process, +you can go through every map in the process, find the PFNs, look those up +in kpagecount, and tally up the number of pages that are only referenced +once. + +Exceptions for Shared Memory +============================ + +Page table entries for shared pages are cleared when the pages are zapped or +swapped out. This makes swapped out pages indistinguishable from never-allocated +ones. + +In kernel space, the swap location can still be retrieved from the page cache. +However, values stored only on the normal PTE get lost irretrievably when the +page is swapped out (i.e. SOFT_DIRTY). + +In user space, whether the page is present, swapped or none can be deduced with +the help of lseek and/or mincore system calls. + +lseek() can differentiate between accessed pages (present or swapped out) and +holes (none/non-allocated) by specifying the SEEK_DATA flag on the file where +the pages are backed. For anonymous shared pages, the file can be found in +``/proc/pid/map_files/``. + +mincore() can differentiate between pages in memory (present, including swap +cache) and out of memory (swapped out or none/non-allocated). + +Other notes +=========== + +Reading from any of the files will return -EINVAL if you are not starting +the read on an 8-byte boundary (e.g., if you sought an odd number of bytes +into the file), or if the size of the read is not a multiple of 8 bytes. + +Before Linux 3.11 pagemap bits 55-60 were used for "page-shift" (which is +always 12 at most architectures). Since Linux 3.11 their meaning changes +after first clear of soft-dirty bits. Since Linux 4.2 they are used for +flags unconditionally. |