diff options
| author | Eric Dumazet <edumazet@google.com> | 2015-06-30 15:54:08 +0200 |
|---|---|---|
| committer | Mister Oyster <oysterized@gmail.com> | 2017-12-31 03:25:06 +0100 |
| commit | ea776cc85615113b780fc6126aa0c7601209cf50 (patch) | |
| tree | 78448894bbb7a1d1c32621ca83a3b6c7dce64f38 /include/linux/fdtable.h | |
| parent | e5983e9c4e1c61b347aeda7243266bee387a40e1 (diff) | |
fs/file.c: don't acquire files->file_lock in fd_install()
Mateusz Guzik reported :
Currently obtaining a new file descriptor results in locking fdtable
twice - once in order to reserve a slot and second time to fill it.
Holding the spinlock in __fd_install() is needed in case a resize is
done, or to prevent a resize.
Mateusz provided an RFC patch and a micro benchmark :
http://people.redhat.com/~mguzik/pipebench.c
A resize is an unlikely operation in a process lifetime,
as table size is at least doubled at every resize.
We can use RCU instead of the spinlock.
__fd_install() must wait if a resize is in progress.
The resize must block new __fd_install() callers from starting,
and wait that ongoing install are finished (synchronize_sched())
resize should be attempted by a single thread to not waste resources.
rcu_sched variant is used, as __fd_install() and expand_fdtable() run
from process context.
It gives us a ~30% speedup using pipebench on a dual Intel(R) Xeon(R)
CPU E5-2696 v2 @ 2.50GHz
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Mateusz Guzik <mguzik@redhat.com>
Acked-by: Mateusz Guzik <mguzik@redhat.com>
Tested-by: Mateusz Guzik <mguzik@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
[@nathanchance: Leave out documentation, https://github.com/torvalds/linux/commit/8a81252b774b53e628a8a0fe18e2b8fc236d92cc]
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Signed-off-by: Joe Maples <joe@frap129.org>
Diffstat (limited to 'include/linux/fdtable.h')
| -rw-r--r-- | include/linux/fdtable.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 9bf15b13f..cb674d6d6 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -48,6 +48,9 @@ struct files_struct { * read mostly part */ atomic_t count; + bool resize_in_progress; + wait_queue_head_t resize_wait; + struct fdtable __rcu *fdt; struct fdtable fdtab; /* |