[Cc fsdevel and lkml] On Tue 18-06-19 23:24:18, Song Liu wrote: > Changes v2 => v3: > 1. Removed the limitation (cannot write to file with THP) by truncating > whole file during sys_open (see 6/6); > 2. Fixed a VM_BUG_ON_PAGE() in filemap_fault() (see 2/6); > 3. Split function rename to a separate patch (Rik); > 4. Updated condition in hugepage_vma_check() (Rik). > > Changes v1 => v2: > 1. Fixed a missing mem_cgroup_commit_charge() for non-shmem case. > > This set follows up discussion at LSF/MM 2019. The motivation is to put > text section of an application in THP, and thus reduces iTLB miss rate and > improves performance. Both Facebook and Oracle showed strong interests to > this feature. > > To make reviews easier, this set aims a mininal valid product. Current > version of the work does not have any changes to file system specific > code. This comes with some limitations (discussed later). > > This set enables an application to "hugify" its text section by simply > running something like: > > madvise(0x600000, 0x80000, MADV_HUGEPAGE); > > Before this call, the /proc/<pid>/maps looks like: > > 00400000-074d0000 r-xp 00000000 00:27 2006927 app > > After this call, part of the text section is split out and mapped to > THP: > > 00400000-00425000 r-xp 00000000 00:27 2006927 app > 00600000-00e00000 r-xp 00200000 00:27 2006927 app <<< on THP > 00e00000-074d0000 r-xp 00a00000 00:27 2006927 app > > Limitations: > > 1. This only works for text section (vma with VM_DENYWRITE). > 2. Original limitation #2 is removed in v3. > > We gated this feature with an experimental config, READ_ONLY_THP_FOR_FS. > Once we get better support on the write path, we can remove the config and > enable it by default. > > Tested cases: > 1. Tested with btrfs and ext4. > 2. Tested with real work application (memcache like caching service). > 3. Tested with "THP aware uprobe": > https://patchwork.kernel.org/project/linux-mm/list/?series=131339 > > Please share your comments and suggestions on this. > > Thanks! > > Song Liu (6): > filemap: check compound_head(page)->mapping in filemap_fault() > filemap: update offset check in filemap_fault() > mm,thp: stats for file backed THP > khugepaged: rename collapse_shmem() and khugepaged_scan_shmem() > mm,thp: add read-only THP support for (non-shmem) FS > mm,thp: handle writes to file with THP in pagecache > > fs/inode.c | 3 ++ > fs/proc/meminfo.c | 4 ++ > include/linux/fs.h | 31 ++++++++++++ > include/linux/mmzone.h | 2 + > mm/Kconfig | 11 +++++ > mm/filemap.c | 9 ++-- > mm/khugepaged.c | 104 +++++++++++++++++++++++++++++++++-------- > mm/rmap.c | 12 +++-- > mm/truncate.c | 7 ++- > mm/vmstat.c | 2 + > 10 files changed, 156 insertions(+), 29 deletions(-) > > -- > 2.17.1 -- Michal Hocko SUSE Labs
