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Initializing a char array to "" is equivalent to a memset()
call - which is exactly what it gets compiled to.
Fixing this one callsite reduced memset() _user_ cpu cycles
from 2-4% to 0.05% on the EeePC.
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
This crops up in my threaded udevd profiles from time to time.
It's not consistent - probably due to variations in the number
of concurrent events - but it can hit 4% user time and higher.
The change halves the user time spent in compare_devpath().
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
The wait should be ordered after matching KERNEL, ENV, etc.
but before ATTR.
Without this, WAIT_FOR_SYSFS rules will be applied unconditionally
to all events.
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Re: b99028c963 shrink struct udev_event
TEST 136: test multi matches 2
device '/devices/pci0000:00/0000:00:1d.7/usb5/5-2/5-2:1.0/tty/ttyACM0' expecting node 'right'
==15011==
==15011== 7 bytes in 1 blocks are definitely lost in loss record 1 of 1
==15011== at 0x47F9AB8: malloc (vg_replace_malloc.c:207)
==15011== by 0x489CB5F: strdup (in /lib32/libc-2.7.so)
==15011== by 0x8050F40: udev_rules_apply_to_event (udev-rules.c:1973)
==15011== by 0x804A658: udev_event_execute_rules (udev-event.c:549)
==15011== by 0x805A636: main (test-udev.c:100)
add: ok
==15012==
==15012== 7 bytes in 1 blocks are definitely lost in loss record 1 of 1
==15012== at 0x47F1AB8: malloc (vg_replace_malloc.c:207)
==15012== by 0x4898B5F: strdup (in /lib32/libc-2.7.so)
==15012== by 0x8050F40: udev_rules_apply_to_event (udev-rules.c:1973)
==15012== by 0x804A9DF: udev_event_execute_rules (udev-event.c:658)
==15012== by 0x805A636: main (test-udev.c:100)
remove: ok
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
The in-memory rule array of a common desktop distro install took:
1151088 bytes
with the token list:
109232 bytes tokens (6827 * 16 bytes), 71302 bytes buffer
The problem was strncpy() doesn't stop after writing the terminating
NUL; by definition it goes on to zero the entire buffer.
I spy another use of strncpy in udev_device_add_property_from_string(),
which is responsible for another ~1% user cpu time...
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Since we already know the length, use memcpy() instead.
Measured 2% _user_ cpu time reduction on EeePC coldplug.
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Use calloc to request cleared memory instead.
Kernel and libc conspire to make this more efficient.
Also, replace one malloc() + strcpy() with strdup().
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Unfortunately the linux rmdir implementation unhashes the dentry
even when the directory is not removed. This is apparently by
design (for filesystems that don't allow deleting open files).
Results from time(1) and oprofile follow.
Before:
0.35user 0.90system
samples % image name symbol name
608 9.6738 vmlinux shrink_dcache_parent
293 4.6619 vmlinux copy_page_c
271 4.3119 vmlinux copy_page_range
257 4.0891 udevd udev_rules_iter_next
After:
0.31user 0.67system
samples % image name symbol name
361 5.0419 vmlinux copy_page_range
322 4.4972 udevd udev_rules_iter_next
300 4.1899 vmlinux copy_page_c
Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
