Index of /pub/linux/kernel.org/kernel/people/rml/O_STREAMING
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sha256sums.asc 2023-04-26 06:12 1.0K
v2.4/ 2013-01-26 00:42 -
IN_LIEU 2004-10-27 12:47 77
README 2002-10-08 11:42 1.2K
Attached patch implements an O_STREAMING file I/O flag which enables
manual drop-behind of pages.
If the file has O_STREAMING set then the user has explicitly said "this
is streaming data, I know I will not revisit this, do not cache
anything". So we drop pages from the pagecache before our current
index. We have to fiddle a bit to get writes working since we do
write-behind but the logic is there and it works.
Some numbers. A simple streaming read to verify the pagecache effects:
Streaming 1GB Read (avg of many runs, mem=2GB):
O_STREAMING Wall time Change in Page Cache
Yes 25.58s 0
No 25.55s +835MB
Another read with much more VM pressure:
Streaming 1GB Read (avg of many runs, mem=8M)
O_STREAMING Wall time Change in Page Cache
Yes 25.76s 0
No 29.01s +1MB
And now the kicker:
Kernel compile (make -j2) and concurrent streaming I/O
(avg of two runs, mem=128M):
O_STREAMING Time to complete Kernel Compile
Yes 3m27.863s
No 4m15.818s
This is c/o Andrew Morton.