[RocksDB] Remove old readahead options

Summary: As title.

Test Plan: make check; db_bench

Reviewers: dhruba, MarkCallaghan

CC: leveldb

Differential Revision: https://reviews.facebook.net/D11643

db/db_bench.cc

@@ -292,18 +292,12 @@ static uint64_t FLAGS_WAL_ttl_seconds = 0;
 // Allow buffered io using OS buffers
 static bool FLAGS_use_os_buffer;
 
-// Allow filesystem to do read-aheads
-static bool FLAGS_use_fsreadahead;
-
 // Allow reads to occur via mmap-ing files
 static bool FLAGS_use_mmap_reads;
 
 // Allow writes to occur via mmap-ing files
 static bool FLAGS_use_mmap_writes;
 
-// Allow readaheads to occur for compactions
-static bool FLAGS_use_readahead_compactions;
-
 // Advise random access on table file open
 static bool FLAGS_advise_random_on_open =
   leveldb::Options().advise_random_on_open;
@@ -1158,7 +1152,6 @@ unique_ptr<char []> GenerateKeyFromInt(int v, const char* suffix = "")
 
     // fill storage options
     options.allow_os_buffer = FLAGS_use_os_buffer;
-    options.allow_readahead = FLAGS_use_fsreadahead;
     options.allow_mmap_reads = FLAGS_use_mmap_reads;
     options.allow_mmap_writes = FLAGS_use_mmap_writes;
     options.advise_random_on_open = FLAGS_advise_random_on_open;
@@ -2080,12 +2073,6 @@ int main(int argc, char** argv) {
     } else if (sscanf(argv[i], "--mmap_write=%d%c", &n, &junk) == 1 &&
                (n == 0 || n == 1)) {
       FLAGS_use_mmap_writes = n;
-    } else if (sscanf(argv[i], "--readahead=%d%c", &n, &junk) == 1 &&
-               (n == 0 || n == 1)) {
-      FLAGS_use_fsreadahead = n;
-    } else if (sscanf(argv[i], "--readahead_compactions=%d%c", &n, &junk) == 1&&
-               (n == 0 || n == 1)) {
-      FLAGS_use_readahead_compactions = n;
     } else if (sscanf(argv[i], "--statistics=%d%c", &n, &junk) == 1 &&
                (n == 0 || n == 1)) {
       if (n == 1) {

include/leveldb/options.h

@@ -132,7 +132,7 @@ struct Options {
   int max_write_buffer_number;
 
   // The minimum number of write buffers that will be merged together
-  // before writing to storage.  If set to 1, then 
+  // before writing to storage.  If set to 1, then
   // all write buffers are fushed to L0 as individual files and this increases
   // read amplification because a get request has to check in all of these
   // files. Also, an in-memory merge may result in writing lesser
@@ -416,17 +416,6 @@ struct Options {
   // Default: true
   bool allow_os_buffer;
 
-  // Reading a single block from a file can cause the OS/FS to start
-  // readaheads of other blocks from the file. Default: true
-  // Note: Deprecated
-  bool allow_readahead;
-
-  // The reads triggered by compaction allows data to be readahead
-  // by the OS/FS. This overrides the setting of 'allow_readahead'
-  // for compaction-reads. Default: true
-  // Note: Deprecated
-  bool allow_readahead_compactions;
-
   // Allow the OS to mmap file for reading sst tables. Default: false
   bool allow_mmap_reads;
 

util/options.cc

@@ -65,8 +65,6 @@ Options::Options()
       manifest_preallocation_size(4 * 1024 * 1024),
       purge_redundant_kvs_while_flush(true),
       allow_os_buffer(true),
-      allow_readahead(true),
-      allow_readahead_compactions(true),
       allow_mmap_reads(false),
       allow_mmap_writes(true),
       is_fd_close_on_exec(true),
@@ -126,13 +124,10 @@ Options::Dump(Logger* log) const
     Log(log," Options.db_stats_log_interval: %d",
         db_stats_log_interval);
     Log(log,"       Options.allow_os_buffer: %d", allow_os_buffer);
-    Log(log,"       Options.allow_readahead: %d", allow_readahead);
     Log(log,"      Options.allow_mmap_reads: %d", allow_mmap_reads);
     Log(log,"     Options.allow_mmap_writes: %d", allow_mmap_writes);
     Log(log,"       Options.min_write_buffer_number_to_merge: %d",
         min_write_buffer_number_to_merge);
-    Log(log,"            Options.allow_readahead_compactions: %d",
-        allow_readahead_compactions);
     Log(log,"        Options.purge_redundant_kvs_while_flush: %d",
          purge_redundant_kvs_while_flush);
     Log(log,"           Options.compression_opts.window_bits: %d",
@@ -193,10 +188,6 @@ Options::Dump(Logger* log) const
         purge_redundant_kvs_while_flush);
     Log(log,"                         Options.allow_os_buffer: %d",
         allow_os_buffer);
-    Log(log,"                         Options.allow_readahead: %d",
-        allow_readahead);
-    Log(log,"             Options.allow_readahead_compactions: %d",
-        allow_readahead_compactions);
     Log(log,"                        Options.allow_mmap_reads: %d",
         allow_mmap_reads);
     Log(log,"                       Options.allow_mmap_writes: %d",