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| author | Alexey Dobriyan <adobriyan@gmail.com> | 2018-04-10 16:30:54 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-04-11 10:28:33 -0700 |
| commit | 2f8974243507d9e5b0f214d7668a59a66b93f36c (patch) | |
| tree | daef514c815b0989ca99ccf67d8725d9262c7d56 | |
| parent | 68c3411ff4a4cee53cc854c11ed191eaaf1956ba (diff) | |
| download | linux-2f8974243507d9e5b0f214d7668a59a66b93f36c.tar.bz2 | |
proc: do less stuff under ->pde_unload_lock
Commit ca469f35a8e9ef ("deal with races between remove_proc_entry() and
proc_reg_release()") moved too much stuff under ->pde_unload_lock making
a problem described at series "[PATCH v5] procfs: Improve Scaling in
proc" worse.
While RCU is being figured out, move kfree() out of ->pde_unload_lock.
On my potato, difference is only 0.5% speedup with concurrent
open+read+close of /proc/cmdline, but the effect should be more
noticeable on more capable machines.
$ perf stat -r 16 -- ./proc-j 16
Performance counter stats for './proc-j 16' (16 runs):
130569.502377 task-clock (msec) # 15.872 CPUs utilized ( +- 0.05% )
19,169 context-switches # 0.147 K/sec ( +- 0.18% )
15 cpu-migrations # 0.000 K/sec ( +- 3.27% )
437 page-faults # 0.003 K/sec ( +- 1.25% )
300,172,097,675 cycles # 2.299 GHz ( +- 0.05% )
96,793,267,308 instructions # 0.32 insn per cycle ( +- 0.04% )
22,798,342,298 branches # 174.607 M/sec ( +- 0.04% )
111,764,687 branch-misses # 0.49% of all branches ( +- 0.47% )
8.226574400 seconds time elapsed ( +- 0.05% )
^^^^^^^^^^^
$ perf stat -r 16 -- ./proc-j 16
Performance counter stats for './proc-j 16' (16 runs):
129866.777392 task-clock (msec) # 15.869 CPUs utilized ( +- 0.04% )
19,154 context-switches # 0.147 K/sec ( +- 0.66% )
14 cpu-migrations # 0.000 K/sec ( +- 1.73% )
431 page-faults # 0.003 K/sec ( +- 1.09% )
298,556,520,546 cycles # 2.299 GHz ( +- 0.04% )
96,525,366,833 instructions # 0.32 insn per cycle ( +- 0.04% )
22,730,194,043 branches # 175.027 M/sec ( +- 0.04% )
111,506,074 branch-misses # 0.49% of all branches ( +- 0.18% )
8.183629778 seconds time elapsed ( +- 0.04% )
^^^^^^^^^^^
Link: http://lkml.kernel.org/r/20180213132911.GA24298@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/proc/inode.c | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 6e8724958116..8118ce5df5c6 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -138,7 +138,7 @@ static void unuse_pde(struct proc_dir_entry *pde) complete(pde->pde_unload_completion); } -/* pde is locked */ +/* pde is locked on entry, unlocked on exit */ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo) { /* @@ -157,9 +157,10 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo) pdeo->c = &c; spin_unlock(&pde->pde_unload_lock); wait_for_completion(&c); - spin_lock(&pde->pde_unload_lock); } else { struct file *file; + struct completion *c; + pdeo->closing = true; spin_unlock(&pde->pde_unload_lock); file = pdeo->file; @@ -167,8 +168,10 @@ static void close_pdeo(struct proc_dir_entry *pde, struct pde_opener *pdeo) spin_lock(&pde->pde_unload_lock); /* After ->release. */ list_del(&pdeo->lh); - if (unlikely(pdeo->c)) - complete(pdeo->c); + c = pdeo->c; + spin_unlock(&pde->pde_unload_lock); + if (unlikely(c)) + complete(c); kfree(pdeo); } } @@ -188,6 +191,7 @@ void proc_entry_rundown(struct proc_dir_entry *de) struct pde_opener *pdeo; pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh); close_pdeo(de, pdeo); + spin_lock(&de->pde_unload_lock); } spin_unlock(&de->pde_unload_lock); } @@ -375,7 +379,7 @@ static int proc_reg_release(struct inode *inode, struct file *file) list_for_each_entry(pdeo, &pde->pde_openers, lh) { if (pdeo->file == file) { close_pdeo(pde, pdeo); - break; + return 0; } } spin_unlock(&pde->pde_unload_lock); |