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Capture ability of BufferedReader to provide contiguous min len buffers as a trait #6921

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Merged
kskalski merged 10 commits into from
Jul 21, 2025
Merged

Capture ability of BufferedReader to provide contiguous min len buffers as a trait #6921

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f8af243
Add trait for BufferedReader
kskalski Jul 10, 2025
55096dd
Use trait. Add max supported len.
kskalski Jul 10, 2025
80c314f
Clippy
kskalski Jul 10, 2025
cd9064d
Rework the BufferedReader and trait.
kskalski Jul 11, 2025
4d17fe6
Always set len of the overflow buffer.
kskalski Jul 11, 2025
8dc5490
Move back capacity tuning.
kskalski Jul 14, 2025
c365ec8
Rename constant.
kskalski Jul 16, 2025
27263c4
Remove explicit lifetime
kskalski Jul 16, 2025
02cd2a0
Fix handling resize / capacity reservation for overflow buffer.
kskalski Jul 17, 2025
e75d483
Update rand generated accounts_vec test to use more large accounts.
kskalski Jul 18, 2025
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102 changes: 38 additions & 64 deletions accounts-db/src/append_vec.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ use {
StoredAccountsInfo,
},
accounts_hash::AccountHash,
buffered_reader::{BufferedReader, Stack},
buffered_reader::{BufferedReader, ContiguousBufFileRead, Stack},
file_io::read_into_buffer,
is_zero_lamport::IsZeroLamport,
storable_accounts::StorableAccounts,
Expand Down Expand Up @@ -1049,19 +1049,17 @@ impl AppendVec {
{}
}
AppendVecFileBacking::File(file) => {
let self_len = self.len();
const BUFFER_SIZE: usize = PAGE_SIZE * 8;
let mut reader = BufferedReader::<Stack<BUFFER_SIZE>>::new_stack(
self_len,
file,
STORE_META_OVERHEAD,
);
let mut reader = BufferedReader::<Stack<BUFFER_SIZE>>::new_stack(self.len(), file);
let mut min_buf_len = STORE_META_OVERHEAD;
// Buffer for account data that doesn't fit within the stack allocated buffer.
// This will be re-used for each account that doesn't fit within the stack allocated buffer.
let mut data_overflow_buffer = vec![];
loop {
let offset = reader.get_offset();
let bytes = match reader.fill_buf() {
let offset = reader.get_file_offset();
let bytes = match reader
.fill_buf_required_or_overflow(min_buf_len, &mut data_overflow_buffer)
{
Ok([]) => break,
Ok(bytes) => ValidSlice::new(bytes),
Err(err) if err.kind() == std::io::ErrorKind::UnexpectedEof => break,
Expand All @@ -1087,53 +1085,26 @@ impl AppendVec {
};
callback(account);
reader.consume(stored_size);
} else if STORE_META_OVERHEAD + data_len <= BUFFER_SIZE {
reader.set_required_data_len(STORE_META_OVERHEAD + data_len);
// restore default required buffer size
min_buf_len = STORE_META_OVERHEAD;
} else {
const MAX_CAPACITY: usize = MAX_PERMITTED_DATA_LENGTH as usize;
// 128KiB covers a reasonably large distribution of typical account sizes.
// In a recent sample, 99.98% of accounts' data lengths were less than or equal to 128KiB.
const MIN_CAPACITY: usize = 1024 * 128;
let capacity = data_overflow_buffer.capacity();
if data_len > capacity {
let next_cap = data_len
.next_power_of_two()
.clamp(MIN_CAPACITY, MAX_CAPACITY);
data_overflow_buffer.reserve_exact(next_cap - capacity);
// SAFETY: We only write to the uninitialized portion of the buffer via `copy_from_slice` and `read_into_buffer`.
// Later, we ensure we only read from the initialized portion of the buffer.
unsafe {
data_overflow_buffer.set_len(next_cap);
// repeat loop with required buffer size holding whole account data
min_buf_len = STORE_META_OVERHEAD + data_len;

if min_buf_len > BUFFER_SIZE {
const MAX_CAPACITY: usize =
STORE_META_OVERHEAD + MAX_PERMITTED_DATA_LENGTH as usize;
// 128KiB covers a reasonably large distribution of typical account sizes.
// In a recent sample, 99.98% of accounts' data lengths were less than or equal to 128KiB.
const MIN_CAPACITY: usize = 1024 * 128;
if min_buf_len > data_overflow_buffer.capacity() {
let next_cap = min_buf_len
.next_power_of_two()
.clamp(MIN_CAPACITY, MAX_CAPACITY);
data_overflow_buffer
.reserve_exact(next_cap - data_overflow_buffer.len());
}
}

// Copy already read data to overflow buffer.
data_overflow_buffer[..leftover].copy_from_slice(&bytes.0[next..]);

// Read remaining data into overflow buffer.
let Ok(bytes_read) = read_into_buffer(
file,
self_len,
offset + next + leftover,
&mut data_overflow_buffer[leftover..data_len],
) else {
break;
};
if bytes_read + leftover < data_len {
break;
}
let data = &data_overflow_buffer[..data_len];
let stored_size = aligned_stored_size(data_len);
let account = StoredAccountMeta {
meta,
account_meta,
data,
offset,
stored_size,
hash,
};
callback(account);
reader.consume(stored_size);
}
}
}
Expand Down Expand Up @@ -1252,14 +1223,12 @@ impl AppendVec {
AppendVecFileBacking::File(file) => {
// Heuristic observed in benchmarking that maintains a reasonable balance between syscalls and data waste
const BUFFER_SIZE: usize = PAGE_SIZE * 4;
let mut reader = BufferedReader::<Stack<BUFFER_SIZE>>::new_stack(
self_len,
file,
mem::size_of::<StoredMeta>() + mem::size_of::<AccountMeta>(),
);
let mut reader = BufferedReader::<Stack<BUFFER_SIZE>>::new_stack(self_len, file);
const REQUIRED_READ_LEN: usize =
mem::size_of::<StoredMeta>() + mem::size_of::<AccountMeta>();
loop {
let offset = reader.get_offset();
let bytes = match reader.fill_buf() {
let offset = reader.get_file_offset();
let bytes = match reader.fill_buf_required(REQUIRED_READ_LEN) {
Ok([]) => break,
Ok(bytes) => ValidSlice::new(bytes),
Err(err) if err.kind() == std::io::ErrorKind::UnexpectedEof => break,
Expand Down Expand Up @@ -1703,12 +1672,17 @@ pub mod tests {

let mut test_accounts = Vec::with_capacity(num_accounts);
let mut file_size = 0;
let special_file_interval = num_accounts / 8;
for i in 0..num_accounts {
let data_len = match i {
// ensure one max size account
0 => MAX_PERMITTED_DATA_LENGTH as usize,
// ensure one 64KiB account
x if x == num_accounts - 1 => 1 << 16,
// Create several spread out accounts with varying sizes:
// for (x / special_file_interval) in 0..7 range
x if x % special_file_interval == 0 => {
// mult increases in 0 to 3 range twice
let mult = (x / special_file_interval) % 4;
// and data_len goes over 0..MAX_PERMITTED_DATA_LENGTH range also twice
mult * (MAX_PERMITTED_DATA_LENGTH as usize) / 3
}
// Otherwise use a reasonably small account to avoid long test times
x => x % 256,
};
Expand Down
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