features/bitrot: Throttle filesystem scrubber

This patch introduces multithreaded filesystem scrubber based
on throttling option configured for a particular volume. The
implementation "logically" breaks scanning and scrubbing with
the number of scrubber threads auto-configured depending upon
the throttle configuration. Scanning (crawling) is left single
threaded (per brick) with entries scrubbed in bulk. On reaching
this "bulk" watermark, scanner waits until entries are scrubbed.
Bricks for a particular volume have a set of thread(s) assigned
for scrubbing, with entries for each brick scrubbed in a round
robin fashion to avoid scrub "stalls" when a brick (out of N
bricks) is under active scrubbing.

This mechanism helps us implement "pause/resume" with ease: all
one need to do is to cleanup scrubber threads and let the main
scanner thread "wait" untill scrubbing is resumed (where the
scrubber thread(s) are spawned again), therefore continuing
where we left off (unless we restart the deamons, where crawl
initiates from root directory again, but I guess that's OK).

[
    NOTE:

    Throttling is optional for the signer daemon, without which
    it runs full throttle. However, passing "-DBR_RATE_LIMIT_SIGNER"
    predefined in CFLAGS enables CPU throttling (during checksum
    calculation) thereby avoiding high CPU usage.
]

Subsequent patches would introduce CPU throttling during hash
calculation for scrubber.

> Change-Id: I5701dd6cd4dff27ca3144ac5e3798a2216b39d4f
> BUG: 1207020
> Signed-off-by: Venky Shankar <vshankar@redhat.com>
> Reviewed-on: http://review.gluster.org/10511
> Tested-by: Gluster Build System <jenkins@build.gluster.com>
> Reviewed-by: Vijay Bellur <vbellur@redhat.com>

Change-Id: I5a125b2d0ac7dafd3e278b7fe4c6c9dd07af76dd
Signed-off-by: Venky Shankar <vshankar@redhat.com>
BUG: 1220041
Reviewed-on: http://review.gluster.org/10720
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Gaurav Kumar Garg <ggarg@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/xlators/features/bit-rot/src/stub/bit-rot-stub-mem-types.h b/xlators/features/bit-rot/src/stub/bit-rot-stub-mem-types.h
index bb4030493db..46271407219 100644
--- a/xlators/features/bit-rot/src/stub/bit-rot-stub-mem-types.h
+++ b/xlators/features/bit-rot/src/stub/bit-rot-stub-mem-types.h
@@ -25,6 +25,9 @@ enum br_mem_types {
         gf_br_mt_br_tbf_t,
         gf_br_mt_br_tbf_bucket_t,
         gf_br_mt_br_tbf_throttle_t,
+        gf_br_mt_br_tbf_opspec_t,
+        gf_br_mt_br_scrubber_t,
+        gf_br_mt_br_fsscan_entry_t,
         gf_br_stub_mt_end
 };