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f396550934
This patch makes rclone keep linux page cache usage under control when
uploading local files to remote backends. When opening a file it issues
FADV_SEQUENTIAL to configure read ahead strategy. While reading
the file it issues FADV_DONTNEED every 128kB to free page cache from
already consumed pages.
```
fadvise64(5, 0, 0, POSIX_FADV_SEQUENTIAL) = 0
read(5, "\324\375\251\376\213\361\240\224>\t5E\301\331X\274^\203oA\353\303.2'\206z\177N\27fB"..., 32768) = 32768
read(5, "\361\311\vW!\354_\317hf\276t\307\30L\351\272T\342C\243\370\240\213\355\210\v\221\201\177[\333"..., 32768) = 32768
read(5, ":\371\337Gn\355C\322\334 \253f\373\277\301;\215\n\240\347\305\6N\257\313\4\365\276ANq!"..., 32768) = 32768
read(5, "\312\243\360P\263\242\267H\304\240Y\310\367sT\321\256\6[b\310\224\361\344$Ms\234\5\314\306i"..., 32768) = 32768
fadvise64(5, 0, 131072, POSIX_FADV_DONTNEED) = 0
read(5, "m\251\7a\306\226\366-\v~\"\216\353\342~0\fht\315DK0\236.\\\201!A#\177\320"..., 32768) = 32768
read(5, "\7\324\207,\205\360\376\307\276\254\250\232\21G\323n\255\354\234\257P\322y\3502\37\246\21\334^42"..., 32768) = 32768
read(5, "e{*\225\223R\320\212EG:^\302\377\242\337\10\222J\16A\305\0\353\354\326P\336\357A|-"..., 32768) = 32768
read(5, "n\23XA4*R\352\234\257\364\355Y\204t9T\363\33\357\333\3674\246\221T\360\226\326G\354\374"..., 32768) = 32768
fadvise64(5, 131072, 131072, POSIX_FADV_DONTNEED) = 0
read(5, "SX\331\251}\24\353\37\310#\307|h%\372\34\310\3070YX\250s\2269\242\236\371\302z\357_"..., 32768) = 32768
read(5, "\177\3500\236Y\245\376NIY\177\360p!\337L]\2726\206@\240\246pG\213\254N\274\226\303\357"..., 32768) = 32768
read(5, "\242$*\364\217U\264]\221Y\245\342r\t\253\25Hr\363\263\364\336\322\t\325\325\f\37z\324\201\351"..., 32768) = 32768
read(5, "\2305\242\366\370\203tM\226<\230\25\316(9\25x\2\376\212\346Q\223 \353\225\323\264jf|\216"..., 32768) = 32768
fadvise64(5, 262144, 131072, POSIX_FADV_DONTNEED) = 0
```
Page cache consumption per file can be checked with tools like [pcstat](https://github.com/tobert/pcstat).
This patch does not have a performance impact. Please find below results
of an experiment comparing local copy of 1GB file with and without this
patch.
With the patch:
```
(mmt/fadvise)$ pcstat 1GB.bin.1
+-----------+----------------+------------+-----------+---------+
| Name | Size (bytes) | Pages | Cached | Percent |
|-----------+----------------+------------+-----------+---------|
| 1GB.bin.1 | 1073741824 | 262144 | 0 | 000.000 |
+-----------+----------------+------------+-----------+---------+
(mmt/fadvise)$ taskset -c 0 /usr/bin/time -v ./rclone copy 1GB.bin.1 /var/empty/rclone
Command being timed: "./rclone copy 1GB.bin.1 /var/empty/rclone"
User time (seconds): 13.19
System time (seconds): 1.12
Percent of CPU this job got: 96%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:14.81
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 27660
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 2212
Voluntary context switches: 5755
Involuntary context switches: 9782
Swaps: 0
File system inputs: 4155264
File system outputs: 2097152
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
(mmt/fadvise)$ pcstat 1GB.bin.1
+-----------+----------------+------------+-----------+---------+
| Name | Size (bytes) | Pages | Cached | Percent |
|-----------+----------------+------------+-----------+---------|
| 1GB.bin.1 | 1073741824 | 262144 | 0 | 000.000 |
+-----------+----------------+------------+-----------+---------+
```
Without the patch:
```
(master)$ taskset -c 0 /usr/bin/time -v ./rclone copy 1GB.bin.1 /var/empty/rclone
Command being timed: "./rclone copy 1GB.bin.1 /var/empty/rclone"
User time (seconds): 14.46
System time (seconds): 0.81
Percent of CPU this job got: 93%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:16.41
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 27600
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 2228
Voluntary context switches: 7190
Involuntary context switches: 1980
Swaps: 0
File system inputs: 2097152
File system outputs: 2097152
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
(master)$ pcstat 1GB.bin.1
+-----------+----------------+------------+-----------+---------+
| Name | Size (bytes) | Pages | Cached | Percent |
|-----------+----------------+------------+-----------+---------|
| 1GB.bin.1 | 1073741824 | 262144 | 262144 | 100.000 |
+-----------+----------------+------------+-----------+---------+
```
|
||
|---|---|---|
| .. | ||
| aaaa | ||
| about_unix.go | ||
| about_windows.go | ||
| fadvise_other.go | ||
| fadvise_unix.go | ||
| lchtimes_unix.go | ||
| lchtimes.go | ||
| local_internal_test.go | ||
| local_test.go | ||
| local.go | ||
| preallocate_other.go | ||
| preallocate_unix.go | ||
| preallocate_windows.go | ||
| read_device_other.go | ||
| read_device_unix.go | ||
| remove_other.go | ||
| remove_test.go | ||
| remove_windows.go | ||
| tests_test.go | ||