ericvh commented 1 year ago

On Tuesday, January 24, 2023 3:38:23 AM CET Eric Van Hensbergen wrote:

This is the third version of a patch series which adds a number of features to improve read/write performance in the 9p filesystem. Mostly it focuses on fixing caching to help utilize the recently increased MSIZE limits and also fixes some problematic behavior within the writeback code.

All together, these show roughly 10x speed increases on simple file transfers. Future patch sets will improve cache consistency and directory caching.

These patches are also available on github: https://github.com/v9fs/linux/tree/ericvh/for-next and on kernel.org: https://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs.git

Tested against qemu, cpu, and diod with fsx, dbench, and some simple benchmarks.

Looks like this needs more work.

I only had a glimpse on your patches yet, but made some tests by doing compilations on guest on top of a 9p root fs [1], msize=500k. Under that scenario:

loose: this is suprisingly the only mode where I can see some performance increase, over "loose" on master it compiled ~5% faster, but I also got some misbehaviours on guest.
writeahead: no performance results, as compilation already aborts when trying to detect a compiler. I had to restore a previous snapshot to repair things after this test.
readahead: significant performance drop. In comparison to "loose" on master compilation takes 6 times longer with "readahead". There are some severe misbehaviours on guest as well, and after boot I get this warning:

[ 5.782846] folio expected an open fid inode->i_private=0000000000000000 [ 5.786641] WARNING: CPU: 0 PID: 321 at fs/9p/vfs_addr.c:174 v9fs_vfs_write_folio_locked (fs/9p/vfs_addr.c:174 (discriminator 3)) 9p [ 5.792496] Modules linked in: ppdev(E) bochs(E) sg(E) drm_vram_helper(E) joydev(E) evdev(E) drm_kms_helper(E) serio_raw(E) drm_ttm_helper(E) pcsp) [ 5.816806] CPU: 0 PID: 321 Comm: chown Tainted: G E 6.2.0-rc6+ #61 [ 5.821694] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014 [ 5.827362] RIP: 0010:v9fs_vfs_write_folio_locked (fs/9p/vfs_addr.c:174 (discriminator 3)) 9p

Code starting with the faulting instruction

...

[ 5.835360] RSP: 0018:ffffc900007d3a38 EFLAGS: 00010282 [ 5.836982] RAX: 0000000000000000 RBX: ffff888106c86680 RCX: 0000000000000000 [ 5.838877] RDX: 0000000000000001 RSI: ffffffff821eb1e6 RDI: 00000000ffffffff [ 5.841179] RBP: ffffea0004279300 R08: 0000000000000000 R09: 00000000ffffefff [ 5.843039] R10: ffffc900007d38e8 R11: ffffffff824bede8 R12: 0000000000000000 [ 5.844850] R13: 00000000ffffffea R14: 0000000000000014 R15: 0000000000000014 [ 5.846366] FS: 00007fd0fc4a0580(0000) GS:ffff88842fc00000(0000) knlGS:0000000000000000 [ 5.848250] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 5.849386] CR2: 00007fd0fc38f4f0 CR3: 0000000100302000 CR4: 00000000000006f0 [ 5.850824] Call Trace: [ 5.851622] [ 5.852052] v9fs_vfs_writepage (fs/9p/vfs_addr.c:207) 9p [ 5.852841] writepage (mm/page-writeback.c:2537) [ 5.853438] write_cache_pages (mm/page-writeback.c:2473) [ 5.854205] ? pfx_writepage (mm/page-writeback.c:2535) [ 5.855309] ? delete_node (lib/radix-tree.c:575) [ 5.856122] ? radix_tree_delete_item (lib/radix-tree.c:1432) [ 5.857101] do_writepages (mm/page-writeback.c:2564 mm/page-writeback.c:2552 mm/page-writeback.c:2583) [ 5.857954] ? radix_tree_delete_item (lib/radix-tree.c:1432) [ 5.859103] filemap_fdatawrite_wbc (mm/filemap.c:389 mm/filemap.c:378) [ 5.860043] __filemap_fdatawrite_range (mm/filemap.c:422) [ 5.861050] filemap_write_and_wait_range (mm/filemap.c:682 mm/filemap.c:665) [ 5.862132] v9fs_vfs_setattr_dotl (./include/linux/pagemap.h:60 fs/9p/vfs_inode_dotl.c:583) 9p [ 5.863312] notify_change (fs/attr.c:486) [ 5.864043] ? chown_common (fs/open.c:736) [ 5.864793] chown_common (fs/open.c:736) [ 5.865538] ? preempt_count_add (./include/linux/ftrace.h:977 kernel/sched/core.c:5737 kernel/sched/core.c:5734 kernel/sched/core.c:5762) [ 5.866420] do_fchownat (fs/open.c:768) [ 5.867419] x64_sys_fchownat (fs/open.c:782 fs/open.c:779 fs/open.c:779) [ 5.868319] do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) [ 5.869116] entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) [ 5.871008] RIP: 0033:0x7fd0fc3b7b9a

Best regards, Christian Schoenebeck

[1] https://wiki.qemu.org/Documentation/9p_root_fs

ericvh commented 1 year ago

fixed everything except for fscache

ericvh commented 1 year ago

should now be fixed for fscache in for-next

v9fs / linux

for-next: issues when running as qemu root in various caching modes #26

Code starting with the faulting instruction