diff options
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/cgroup-v1/memory.rst | 19 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 40 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/hugetlbpage.rst | 35 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/transhuge.rst | 7 | ||||
| -rw-r--r-- | Documentation/admin-guide/sysctl/vm.rst | 23 |
5 files changed, 94 insertions, 30 deletions
diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst index 0ae4f564c2d6..12757e63b26c 100644 --- a/Documentation/admin-guide/cgroup-v1/memory.rst +++ b/Documentation/admin-guide/cgroup-v1/memory.rst @@ -199,11 +199,11 @@ An RSS page is unaccounted when it's fully unmapped. A PageCache page is unaccounted when it's removed from radix-tree. Even if RSS pages are fully unmapped (by kswapd), they may exist as SwapCache in the system until they are really freed. Such SwapCaches are also accounted. -A swapped-in page is not accounted until it's mapped. +A swapped-in page is accounted after adding into swapcache. Note: The kernel does swapin-readahead and reads multiple swaps at once. -This means swapped-in pages may contain pages for other tasks than a task -causing page fault. So, we avoid accounting at swap-in I/O. +Since page's memcg recorded into swap whatever memsw enabled, the page will +be accounted after swapin. At page migration, accounting information is kept. @@ -222,18 +222,13 @@ the cgroup that brought it in -- this will happen on memory pressure). But see section 8.2: when moving a task to another cgroup, its pages may be recharged to the new cgroup, if move_charge_at_immigrate has been chosen. -Exception: If CONFIG_MEMCG_SWAP is not used. -When you do swapoff and make swapped-out pages of shmem(tmpfs) to -be backed into memory in force, charges for pages are accounted against the -caller of swapoff rather than the users of shmem. - -2.4 Swap Extension (CONFIG_MEMCG_SWAP) +2.4 Swap Extension -------------------------------------- -Swap Extension allows you to record charge for swap. A swapped-in page is -charged back to original page allocator if possible. +Swap usage is always recorded for each of cgroup. Swap Extension allows you to +read and limit it. -When swap is accounted, following files are added. +When CONFIG_SWAP is enabled, following files are added. - memory.memsw.usage_in_bytes. - memory.memsw.limit_in_bytes. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a76d83ed5262..0b4b9e1e35b6 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -834,12 +834,15 @@ See also Documentation/networking/decnet.rst. default_hugepagesz= - [same as hugepagesz=] The size of the default - HugeTLB page size. This is the size represented by - the legacy /proc/ hugepages APIs, used for SHM, and - default size when mounting hugetlbfs filesystems. - Defaults to the default architecture's huge page size - if not specified. + [HW] The size of the default HugeTLB page. This is + the size represented by the legacy /proc/ hugepages + APIs. In addition, this is the default hugetlb size + used for shmget(), mmap() and mounting hugetlbfs + filesystems. If not specified, defaults to the + architecture's default huge page size. Huge page + sizes are architecture dependent. See also + Documentation/admin-guide/mm/hugetlbpage.rst. + Format: size[KMG] deferred_probe_timeout= [KNL] Debugging option to set a timeout in seconds for @@ -1484,13 +1487,24 @@ hugepages using the cma allocator. If enabled, the boot-time allocation of gigantic hugepages is skipped. - hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot. - hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages. - On x86-64 and powerpc, this option can be specified - multiple times interleaved with hugepages= to reserve - huge pages of different sizes. Valid pages sizes on - x86-64 are 2M (when the CPU supports "pse") and 1G - (when the CPU supports the "pdpe1gb" cpuinfo flag). + hugepages= [HW] Number of HugeTLB pages to allocate at boot. + If this follows hugepagesz (below), it specifies + the number of pages of hugepagesz to be allocated. + If this is the first HugeTLB parameter on the command + line, it specifies the number of pages to allocate for + the default huge page size. See also + Documentation/admin-guide/mm/hugetlbpage.rst. + Format: <integer> + + hugepagesz= + [HW] The size of the HugeTLB pages. This is used in + conjunction with hugepages (above) to allocate huge + pages of a specific size at boot. The pair + hugepagesz=X hugepages=Y can be specified once for + each supported huge page size. Huge page sizes are + architecture dependent. See also + Documentation/admin-guide/mm/hugetlbpage.rst. + Format: size[KMG] hung_task_panic= [KNL] Should the hung task detector generate panics. diff --git a/Documentation/admin-guide/mm/hugetlbpage.rst b/Documentation/admin-guide/mm/hugetlbpage.rst index 1cc0bc78d10e..5026e58826e2 100644 --- a/Documentation/admin-guide/mm/hugetlbpage.rst +++ b/Documentation/admin-guide/mm/hugetlbpage.rst @@ -100,6 +100,41 @@ with a huge page size selection parameter "hugepagesz=<size>". <size> must be specified in bytes with optional scale suffix [kKmMgG]. The default huge page size may be selected with the "default_hugepagesz=<size>" boot parameter. +Hugetlb boot command line parameter semantics +hugepagesz - Specify a huge page size. Used in conjunction with hugepages + parameter to preallocate a number of huge pages of the specified + size. Hence, hugepagesz and hugepages are typically specified in + pairs such as: + hugepagesz=2M hugepages=512 + hugepagesz can only be specified once on the command line for a + specific huge page size. Valid huge page sizes are architecture + dependent. +hugepages - Specify the number of huge pages to preallocate. This typically + follows a valid hugepagesz or default_hugepagesz parameter. However, + if hugepages is the first or only hugetlb command line parameter it + implicitly specifies the number of huge pages of default size to + allocate. If the number of huge pages of default size is implicitly + specified, it can not be overwritten by a hugepagesz,hugepages + parameter pair for the default size. + For example, on an architecture with 2M default huge page size: + hugepages=256 hugepagesz=2M hugepages=512 + will result in 256 2M huge pages being allocated and a warning message + indicating that the hugepages=512 parameter is ignored. If a hugepages + parameter is preceded by an invalid hugepagesz parameter, it will + be ignored. +default_hugepagesz - Specify the default huge page size. This parameter can + only be specified once on the command line. default_hugepagesz can + optionally be followed by the hugepages parameter to preallocate a + specific number of huge pages of default size. The number of default + sized huge pages to preallocate can also be implicitly specified as + mentioned in the hugepages section above. Therefore, on an + architecture with 2M default huge page size: + hugepages=256 + default_hugepagesz=2M hugepages=256 + hugepages=256 default_hugepagesz=2M + will all result in 256 2M huge pages being allocated. Valid default + huge page size is architecture dependent. + When multiple huge page sizes are supported, ``/proc/sys/vm/nr_hugepages`` indicates the current number of pre-allocated huge pages of the default size. Thus, one can use the following command to dynamically allocate/deallocate diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 2f31de8f7c74..6a233e42be08 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -220,6 +220,13 @@ memory. A lower value can prevent THPs from being collapsed, resulting fewer pages being collapsed into THPs, and lower memory access performance. +``max_ptes_shared`` specifies how many pages can be shared across multiple +processes. Exceeding the number would block the collapse:: + + /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_shared + +A higher value may increase memory footprint for some workloads. + Boot parameter ============== diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 0329a4d3fa9e..d46d5b7013c6 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -831,14 +831,27 @@ tooling to work, you can do:: swappiness ========== -This control is used to define how aggressive the kernel will swap -memory pages. Higher values will increase aggressiveness, lower values -decrease the amount of swap. A value of 0 instructs the kernel not to -initiate swap until the amount of free and file-backed pages is less -than the high water mark in a zone. +This control is used to define the rough relative IO cost of swapping +and filesystem paging, as a value between 0 and 200. At 100, the VM +assumes equal IO cost and will thus apply memory pressure to the page +cache and swap-backed pages equally; lower values signify more +expensive swap IO, higher values indicates cheaper. + +Keep in mind that filesystem IO patterns under memory pressure tend to +be more efficient than swap's random IO. An optimal value will require +experimentation and will also be workload-dependent. The default value is 60. +For in-memory swap, like zram or zswap, as well as hybrid setups that +have swap on faster devices than the filesystem, values beyond 100 can +be considered. For example, if the random IO against the swap device +is on average 2x faster than IO from the filesystem, swappiness should +be 133 (x + 2x = 200, 2x = 133.33). + +At 0, the kernel will not initiate swap until the amount of free and +file-backed pages is less than the high watermark in a zone. + unprivileged_userfaultfd ======================== |