diff options
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/hugetlbpage.txt | 27 | ||||
| -rw-r--r-- | Documentation/vm/zswap.txt | 22 |
2 files changed, 39 insertions, 10 deletions
diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt index 59cbc803aad6..faf077d50d42 100644 --- a/Documentation/vm/hugetlbpage.txt +++ b/Documentation/vm/hugetlbpage.txt @@ -20,19 +20,20 @@ options. The /proc/meminfo file provides information about the total number of persistent hugetlb pages in the kernel's huge page pool. It also displays -information about the number of free, reserved and surplus huge pages and the -default huge page size. The huge page size is needed for generating the -proper alignment and size of the arguments to system calls that map huge page -regions. +default huge page size and information about the number of free, reserved +and surplus huge pages in the pool of huge pages of default size. +The huge page size is needed for generating the proper alignment and +size of the arguments to system calls that map huge page regions. The output of "cat /proc/meminfo" will include lines like: ..... -HugePages_Total: vvv -HugePages_Free: www -HugePages_Rsvd: xxx -HugePages_Surp: yyy -Hugepagesize: zzz kB +HugePages_Total: uuu +HugePages_Free: vvv +HugePages_Rsvd: www +HugePages_Surp: xxx +Hugepagesize: yyy kB +Hugetlb: zzz kB where: HugePages_Total is the size of the pool of huge pages. @@ -47,6 +48,14 @@ HugePages_Surp is short for "surplus," and is the number of huge pages in the pool above the value in /proc/sys/vm/nr_hugepages. The maximum number of surplus huge pages is controlled by /proc/sys/vm/nr_overcommit_hugepages. +Hugepagesize is the default hugepage size (in Kb). +Hugetlb is the total amount of memory (in kB), consumed by huge + pages of all sizes. + If huge pages of different sizes are in use, this number + will exceed HugePages_Total * Hugepagesize. To get more + detailed information, please, refer to + /sys/kernel/mm/hugepages (described below). + /proc/filesystems should also show a filesystem of type "hugetlbfs" configured in the kernel. diff --git a/Documentation/vm/zswap.txt b/Documentation/vm/zswap.txt index 89fff7d611cc..0b3a1148f9f0 100644 --- a/Documentation/vm/zswap.txt +++ b/Documentation/vm/zswap.txt @@ -98,5 +98,25 @@ request is made for a page in an old zpool, it is uncompressed using its original compressor. Once all pages are removed from an old zpool, the zpool and its compressor are freed. +Some of the pages in zswap are same-value filled pages (i.e. contents of the +page have same value or repetitive pattern). These pages include zero-filled +pages and they are handled differently. During store operation, a page is +checked if it is a same-value filled page before compressing it. If true, the +compressed length of the page is set to zero and the pattern or same-filled +value is stored. + +Same-value filled pages identification feature is enabled by default and can be +disabled at boot time by setting the "same_filled_pages_enabled" attribute to 0, +e.g. zswap.same_filled_pages_enabled=0. It can also be enabled and disabled at +runtime using the sysfs "same_filled_pages_enabled" attribute, e.g. + +echo 1 > /sys/module/zswap/parameters/same_filled_pages_enabled + +When zswap same-filled page identification is disabled at runtime, it will stop +checking for the same-value filled pages during store operation. However, the +existing pages which are marked as same-value filled pages remain stored +unchanged in zswap until they are either loaded or invalidated. + A debugfs interface is provided for various statistic about pool size, number -of pages stored, and various counters for the reasons pages are rejected. +of pages stored, same-value filled pages and various counters for the reasons +pages are rejected. |