rclone/backend/local/fadvise_other.go

//+build !linux

package local

import (
	"io"
	"os"
)

func newFadviseReadCloser(o *Object, f *os.File, offset, limit int64) io.ReadCloser {
	return f
}
backend/local: Avoid polluting page cache when uploading local files to remote backends 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$Ms\234\5\314\306i"..., 32768) = 32768 fadvise64(5, 0, 131072, POSIX_FADV_DONTNEED) = 0 read(5, "m\251\7a\306\226\366-\v~\"\216\353\342~0\fht\315DK0\236.\\\201!A#\177\320"..., 32768) = 32768 read(5, "\7\324\207,\205\360\376\307\276\254\250\232\21G\323n\255\354\234\257P\322y\3502\37\246\21\334^42"..., 32768) = 32768 read(5, "e{\225\223R\320\212EG:^\302\377\242\337\10\222J\16A\305\0\353\354\326P\336\357A\|-"..., 32768) = 32768 read(5, "n\23XA4R\352\234\257\364\355Y\204t9T\363\33\357\333\3674\246\221T\360\226\326G\354\374"..., 32768) = 32768 fadvise64(5, 131072, 131072, POSIX_FADV_DONTNEED) = 0 read(5, "SX\331\251}\24\353\37\310#\307\|h%\372\34\310\3070YX\250s\2269\242\236\371\302z\357_"..., 32768) = 32768 read(5, "\177\3500\236Y\245\376NIY\177\360p!\337L]\2726\206@\240\246pG\213\254N\274\226\303\357"..., 32768) = 32768 read(5, "\242$*\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 \| +-----------+----------------+------------+-----------+---------+ ``` 2019-08-06 17:22:57 +08:00			`//+build !linux`

			`package local`

			`import (`
			`"io"`
			`"os"`
			`)`

			`func newFadviseReadCloser(o Object, f os.File, offset, limit int64) io.ReadCloser {`
			`return f`
			`}`