| dfaure | |
| davidedmundson |
| Frameworks |
We had a bad value of 32,768 bytes to copy at once.
But Linux sendfile can support 2,147,479,552 bytes at once.
Increase the amount of data we copy in one sendfile syscall to 5MB so that we still have some copy progress reporting.
CCBUG: 342056
CCBUG: 402276
Tested on my system a fast drive : nvme ssd.
ll test.mkv .rw-rw-r-- 4,3G meven 30 oct. 16:16 test.mkv
Before:
time KDE_FORK_SLAVES=1 /usr/bin/kioclient5 cp file:///home/meven/test.mkv file:///home/meven/testa.mkv real 0m19,583s user 0m0,084s sys 0m0,060s
After:
time KDE_FORK_SLAVES=1 /home/meven/kde/usr/bin/kioclient5 cp file:///home/meven/test.mkv file:///home/meven/testa.mkv real 0m18,488s user 0m0,075s sys 0m0,046s
For reference cp:
time cp test.mkv testa.mkv real 0m18,707s user 0m0,062s sys 0m7,017s
We can be as fast as cp with this, a 5.5% spead increase of large file copy.
Results depend on your system.
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| Buildable 18367 | |
| Build 18385: arc lint + arc unit |
TBH, I would move away from the hardcoding in general.... try to sendfile size_of_file and if n < size use n as new count for the next cycle. The second cycle will use the maximum regardless of what the specific kernel version has as maximum.
The maximum is an implementation detail of the kernel that may change every release, so hardcoding anything seems wrong here.
The bug scope is rather large.
But this will help and I suspect https://phabricator.kde.org/D23523 will too.
| src/ioslaves/file/file_unix.cpp | ||
|---|---|---|
| 55 | man sendfile Found while reviewing code investigating https://bugs.kde.org/show_bug.cgi?id=342056. | |
| 272 | It is used when sendfile call fails to stop using it in next iteration. line 272 - 276 and later | |
Limit sendfile chunk size to 5MB so that users can still follow progress while enjoying faster copy
| src/ioslaves/file/file_unix.cpp | ||
|---|---|---|
| 58 | I have reduced the value to 5 MB so that users can still follow progress, otherwise the progress bar would move every 2,147,479,552 bytes copied. The best value we could have depends on the actual speed of the drive we are writing to, so we can have regular user feedback and maximum speed. In the meantime this patch should help things already. | |
| src/ioslaves/file/file_unix.cpp | ||
|---|---|---|
| 267 | This prevented using sendfile for file bigger than 2 GB. | |