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bees: drop the balance/logical workaround that has been disabled for two years

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Kernels that needed the balance workaround frankly are too buggy
to run bees at all.  The workaround also makes the locking stories
around logical_ino calls and process exit complicated, so get rid of
it completely.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2022-11-19 02:00:17 -05:00
parent 83a2b010e6
commit 9cdeb608f5
3 changed files with 0 additions and 47 deletions
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10
docs/btrfs-kernel.md
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@ -96,16 +96,6 @@ Workarounds for known kernel bugs
at the same time can lead to a kernel hang. The workaround is
to reduce the thread count to 1 with `-c1`.
* **Tree mod log issues**: bees will detect that a btrfs balance is
running, and pause bees activity until the balance is done. This avoids
running both the `LOGICAL_INO` ioctl and btrfs balance at the same time,
which avoids kernel crashes on old kernel versions.
The numbers for "tree mod log issue #" in the above table are arbitrary.
There are a lot of them, and they all behave fairly similarly.
This workaround is less necessary for kernels 5.4.19 and later.
* **Slow backrefs** (aka toxic extents): Under certain conditions,
if the number of references to a single shared extent grows too
high, the kernel consumes more and more CPU while also holding locks

30
src/bees-context.cc
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@ -752,33 +752,6 @@ BeesResolveAddrResult::BeesResolveAddrResult()
{
}
void
BeesContext::wait_for_balance()
{
if (!BEES_SERIALIZE_BALANCE) {
return;
}
Timer balance_timer;
BEESNOTE("WORKAROUND: waiting for balance to stop");
while (true) {
btrfs_ioctl_balance_args args {};
const int ret = ioctl(root_fd(), BTRFS_IOC_BALANCE_PROGRESS, &args);
if (ret < 0) {
// Either can't get balance status or not running, exit either way
break;
}
if (!(args.state & BTRFS_BALANCE_STATE_RUNNING)) {
// Balance not running, doesn't matter if paused or cancelled
break;
}
BEESLOGDEBUG("WORKAROUND: Waiting " << balance_timer << "s for balance to stop");
nanosleep(BEES_BALANCE_POLL_INTERVAL);
}
}
BeesResolveAddrResult
BeesContext::resolve_addr_uncached(BeesAddress addr)
{
@ -790,9 +763,6 @@ BeesContext::resolve_addr_uncached(BeesAddress addr)
// transaction latency, competing threads, and freeze/SIGSTOP
// pausing the bees process.
// Wait for the balance to finish before we run LOGICAL_INO
wait_for_balance();
BtrfsIoctlLogicalInoArgs log_ino(addr.get_physical_or_zero());
// Time how long this takes

7
src/bees.h
View File

@ -108,12 +108,6 @@ const size_t BEES_MAX_CRAWL_BATCH = 128;
// Wait this many transids between crawls
const size_t BEES_TRANSID_FACTOR = 10;
// Wait this long for a balance to stop
const double BEES_BALANCE_POLL_INTERVAL = 60.0;
// Workaround for tree mod log bugs
const bool BEES_SERIALIZE_BALANCE = false;
// Workaround for silly dedupe / ineffective readahead behavior
const size_t BEES_READAHEAD_SIZE = 1024 * 1024;
@ -753,7 +747,6 @@ class BeesContext : public enable_shared_from_this<BeesContext> {
void set_root_fd(Fd fd);
BeesResolveAddrResult resolve_addr_uncached(BeesAddress addr);
void wait_for_balance();
BeesFileRange scan_one_extent(const BeesFileRange &bfr, const Extent &e);
void rewrite_file_range(const BeesFileRange &bfr);