On Wed, Jan 4, 2023 at 3:11 PM Nhat Pham <nphamcs@xxxxxxxxx> wrote: > > Changelog: > v5: > * Separate first patch into its own series. > (suggested by Andrew Morton) > * Expose filemap_cachestat() to non-syscall usage > (patch 2) (suggested by Brian Foster). > * Fix some build errors from last version. > (patch 2) > * Explain eviction and recent eviction in the draft man page and > documentation (suggested by Andrew Morton). > (patch 2) > v4: > * Refactor cachestat and move it to mm/filemap.c (patch 3) > (suggested by Brian Foster) > * Remove redundant checks (!folio, access_ok) > (patch 3) (suggested by Matthew Wilcox and Al Viro) > * Fix a bug in handling multipages folio. > (patch 3) (suggested by Matthew Wilcox) > * Add a selftest for shmem files, which can be used to test huge > pages (patch 4) (suggested by Johannes Weiner) > v3: > * Fix some minor formatting issues and build errors. > * Add the new syscall entry to missing architecture syscall tables. > (patch 3). > * Add flags argument for the syscall. (patch 3). > * Clean up the recency refactoring (patch 2) (suggested by Yu Zhao) > * Add the new Kconfig (CONFIG_CACHESTAT) to disable the syscall. > (patch 3) (suggested by Josh Triplett) > v2: > * len == 0 means query to EOF. len < 0 is invalid. > (patch 3) (suggested by Brian Foster) > * Make cachestat extensible by adding the `cstat_size` argument in the > syscall (patch 3) > > There is currently no good way to query the page cache state of large > file sets and directory trees. There is mincore(), but it scales poorly: > the kernel writes out a lot of bitmap data that userspace has to > aggregate, when the user really doesn not care about per-page information > in that case. The user also needs to mmap and unmap each file as it goes > along, which can be quite slow as well. > > This series of patches introduces a new system call, cachestat, that > summarizes the page cache statistics (number of cached pages, dirty > pages, pages marked for writeback, evicted pages etc.) of a file, in a > specified range of bytes. It also include a selftest suite that tests some > typical usage > > This interface is inspired by past discussion and concerns with fincore, > which has a similar design (and as a result, issues) as mincore. > Relevant links: > > https://lkml.indiana.edu/hypermail/linux/kernel/1302.1/04207.html > https://lkml.indiana.edu/hypermail/linux/kernel/1302.1/04209.html > > For comparison with mincore, I ran both syscalls on a 2TB sparse file: > > Using mincore: > real 0m37.510s > user 0m2.934s > sys 0m34.558s > > Using cachestat: > real 0m0.009s > user 0m0.000s > sys 0m0.009s > > This series should be applied on top of: > > workingset: fix confusion around eviction vs refault container > https://lkml.org/lkml/2023/1/4/1066 > > This series consist of 3 patches: > > Nhat Pham (3): > workingset: refactor LRU refault to expose refault recency check > cachestat: implement cachestat syscall > selftests: Add selftests for cachestat > > MAINTAINERS | 7 + > arch/alpha/kernel/syscalls/syscall.tbl | 1 + > arch/arm/tools/syscall.tbl | 1 + > arch/ia64/kernel/syscalls/syscall.tbl | 1 + > arch/m68k/kernel/syscalls/syscall.tbl | 1 + > arch/microblaze/kernel/syscalls/syscall.tbl | 1 + > arch/parisc/kernel/syscalls/syscall.tbl | 1 + > arch/powerpc/kernel/syscalls/syscall.tbl | 1 + > arch/s390/kernel/syscalls/syscall.tbl | 1 + > arch/sh/kernel/syscalls/syscall.tbl | 1 + > arch/sparc/kernel/syscalls/syscall.tbl | 1 + > arch/x86/entry/syscalls/syscall_32.tbl | 1 + > arch/x86/entry/syscalls/syscall_64.tbl | 1 + > arch/xtensa/kernel/syscalls/syscall.tbl | 1 + > include/linux/fs.h | 3 + > include/linux/swap.h | 1 + > include/linux/syscalls.h | 3 + > include/uapi/asm-generic/unistd.h | 5 +- > include/uapi/linux/mman.h | 9 + > init/Kconfig | 10 + > kernel/sys_ni.c | 1 + > mm/filemap.c | 143 ++++++++++ > mm/workingset.c | 129 ++++++--- > tools/testing/selftests/Makefile | 1 + > tools/testing/selftests/cachestat/.gitignore | 2 + > tools/testing/selftests/cachestat/Makefile | 8 + > .../selftests/cachestat/test_cachestat.c | 259 ++++++++++++++++++ > 27 files changed, 555 insertions(+), 39 deletions(-) > create mode 100644 tools/testing/selftests/cachestat/.gitignore > create mode 100644 tools/testing/selftests/cachestat/Makefile > create mode 100644 tools/testing/selftests/cachestat/test_cachestat.c > > > base-commit: 1440f576022887004f719883acb094e7e0dd4944 > prerequisite-patch-id: 171a43d333e1b267ce14188a5beaea2f313787fb > -- > 2.30.2 Oops, I think I accidentally sent out v5 twice :( Please ignore the first set of emails and review this one only, LKML link for convenience: https://lkml.org/lkml/2023/1/4/1095
