This reduces allocations, in number and in size, while getting extended
attributes. This is mostly noticable when there is a large number of new
files to scan and we're running with the default scanProgressInterval --
then a queue of files is built in-memory, and this queue includes
extended attributes as part of file metadata. (Arguable it shouldn't,
but that's a more difficult and involved change.)
With 1M files to scan, each with one extended attribute, current peak
memory usage looks like this:
Showing nodes accounting for 1425.30MB, 98.19% of 1451.64MB total
Dropped 1435 nodes (cum <= 7.26MB)
Showing top 10 nodes out of 54
flat flat% sum% cum cum%
976.56MB 67.27% 67.27% 976.56MB 67.27%
github.com/syncthing/syncthing/lib/fs.getXattr
305.44MB 21.04% 88.31% 305.44MB 21.04%
github.com/syncthing/syncthing/lib/scanner.(*walker).walk.func1
45.78MB 3.15% 91.47% 1045.23MB 72.00%
github.com/syncthing/syncthing/lib/fs.(*BasicFilesystem).GetXattr
22.89MB 1.58% 93.04% 22.89MB 1.58%
github.com/syncthing/syncthing/lib/fs.listXattr
22.89MB 1.58% 94.62% 22.89MB 1.58%
github.com/syncthing/syncthing/lib/protocol.(*PlatformData).SetXattrs
16MB 1.10% 95.72% 16.01MB 1.10%
github.com/syndtr/goleveldb/leveldb/memdb.New
After the change, it's this:
Showing nodes accounting for 502.32MB, 95.70% of 524.88MB total
Dropped 1400 nodes (cum <= 2.62MB)
Showing top 10 nodes out of 91
flat flat% sum% cum cum%
305.43MB 58.19% 58.19% 305.43MB 58.19%
github.com/syncthing/syncthing/lib/scanner.(*walker).walk.func1
45.79MB 8.72% 66.91% 68.68MB 13.09%
github.com/syncthing/syncthing/lib/fs.(*BasicFilesystem).GetXattr
32MB 6.10% 73.01% 32.01MB 6.10%
github.com/syndtr/goleveldb/leveldb/memdb.New
22.89MB 4.36% 77.37% 22.89MB 4.36%
github.com/syncthing/syncthing/lib/fs.listXattr
22.89MB 4.36% 81.73% 22.89MB 4.36%
github.com/syncthing/syncthing/lib/protocol.(*PlatformData).SetXattrs
15.35MB 2.92% 84.66% 15.36MB 2.93%
github.com/syndtr/goleveldb/leveldb/util.(*BufferPool).Get
15.28MB 2.91% 87.57% 15.28MB 2.91% strings.(*Builder).grow
(The usage for xattrs is reduced from 976 MB to 68 MB)
c1ec9a8826