IMPORTANT API CHANGE: stasis_dirty_page_table_flush_range() no longer force writes to disk. You now need to call forcePageRange() after flush page range returns.

This commit should significantly improve sequential write thoughput.

I found a segfault bug this morning, but cannot reproduce.  Could be a heisenbug, or could have been a hardware fault (gojira repeatedly kernel paniced, then both problems went away...)

benchmarks/sequentialThroughput.c

@@ -33,7 +33,7 @@ int main(int argc, char ** argv) {
   int direct = 0;
   int legacyBM = 0;
   int legacyFH = 0;
-
+  int stake = 0;
   long page_count = mb_to_page(100);
 
   for(int i = 1; i < argc; i++) {
@@ -65,6 +65,9 @@ int main(int argc, char ** argv) {
     } else if(!strcmp(argv[i], "--mb")) {
       i++;
       page_count = mb_to_page(atoll(argv[i]));
+    } else if(!strcmp(argv[i], "--stake")) {
+      i++;
+      stake = mb_to_page(atoll(argv[i]));
     } else {
       printf("Unknown argument: %s\n", argv[i]);
       return 1;
@@ -78,6 +81,14 @@ int main(int argc, char ** argv) {
 
   Tinit();
 
+  if(stake) {
+    Page * p = loadPage(-1, stake);
+    writelock(p->rwlatch,0);
+    stasis_dirty_page_table_set_dirty(stasis_runtime_dirty_page_table(), p);
+    unlock(p->rwlatch);
+    releasePage(p);
+  }
+
   for(long i =0; i < page_count; i++) {
     Page * p = loadPage(-1, i);
     writelock(p->rwlatch,0);

src/stasis/bufferManager/bufferHash.c

@@ -30,6 +30,8 @@ static stasis_buffer_pool_t * stasis_buffer_pool;
 
 static stasis_page_handle_t * page_handle;
 
+static int flushing;
+
 static int running;
 
 typedef struct LL_ENTRY(node_t) node_t;
@@ -49,7 +51,14 @@ static inline struct Page_s ** pagePendingPtr(Page * p) {
 static inline intptr_t* pagePinCountPtr(Page * p) {
   return ((intptr_t*)(&((p)->queue)));
 }
-
+static inline int needFlush() {
+  pageid_t count = stasis_dirty_page_table_dirty_count(stasis_runtime_dirty_page_table());
+  const pageid_t needed = 1000; //MAX_BUFFER_SIZE / 5;
+  if(count > needed) {
+    DEBUG("Need flush?  Dirty: %lld Total: %lld ret = %d\n", count, needed, count > needed);
+  }
+  return  count > needed;
+}
 #ifdef LONG_RUN
 
 inline static void checkPageState(Page * p) {
@@ -96,11 +105,13 @@ inline static int tryToWriteBackPage(pageid_t page) {
   if(*pagePendingPtr(p) || *pagePinCountPtr(p)) {
     return EBUSY;
   }
-
   DEBUG("Write(%ld)\n", (long)victim->id);
   page_handle->write(page_handle, p);  /// XXX pageCleanup and pageFlushed might be heavyweight.
 
-  assert(!stasis_dirty_page_table_is_dirty(stasis_runtime_dirty_page_table(), p));
+//  int locked = trywritelock(p->rwlatch,0);
+//  assert(locked);
+//  assert(!stasis_dirty_page_table_is_dirty(stasis_runtime_dirty_page_table(), p));
+//  unlock(p->rwlatch);
 
   return 0;
 }
@@ -127,7 +138,8 @@ inline static Page * getFreePage() {
       assert(!*pagePendingPtr(ret));
       if(ret->dirty) {
         pthread_mutex_unlock(&mut);
-        stasis_dirty_page_table_flush_range(stasis_runtime_dirty_page_table(), 0, 0);
+        DEBUG("Blocking app thread");
+        stasis_dirty_page_table_flush(stasis_runtime_dirty_page_table());
         pthread_mutex_lock(&mut);
       } else {
         break;
@@ -148,12 +160,17 @@ inline static Page * getFreePage() {
 static void * writeBackWorker(void * ignored) {
   pthread_mutex_lock(&mut);
   while(1) {
-    while(running && pageCount < MAX_BUFFER_SIZE) {
+    while(running && (!needFlush())) {
+      flushing = 0;
+      DEBUG("Sleeping in write back worker (count = %lld)\n", stasis_dirty_page_table_dirty_count(stasis_runtime_dirty_page_table()));
       pthread_cond_wait(&needFree, &mut);
+      DEBUG("Woke write back worker (count = %lld)\n", stasis_dirty_page_table_dirty_count(stasis_runtime_dirty_page_table()));
+      flushing = 1;
     }
     if(!running) { break; }
     pthread_mutex_unlock(&mut);
-    stasis_dirty_page_table_flush_range(stasis_runtime_dirty_page_table(), 0, 0);
+    DEBUG("Calling flush\n");
+    stasis_dirty_page_table_flush(stasis_runtime_dirty_page_table());
     pthread_mutex_lock(&mut);
   }
   pthread_mutex_unlock(&mut);
@@ -297,7 +314,7 @@ static Page * bhLoadPageImpl_helper(int xid, const pageid_t pageid, int uninitia
   pthread_cond_broadcast(&readComplete);
 
   // TODO Improve writeback policy
-  if(stasis_dirty_page_table_dirty_count(stasis_runtime_dirty_page_table()) > MAX_BUFFER_SIZE / 5) {
+  if((!flushing) && needFlush()) {
     pthread_cond_signal(&needFree);
   }
   assert(ret->id == pageid);
@@ -339,13 +356,15 @@ static void bhForcePageRange(pageid_t start, pageid_t stop) {
   page_handle->force_range(page_handle, start, stop);
 }
 static void bhBufDeinit() {
+  pthread_mutex_lock(&mut);
   running = 0;
+  pthread_mutex_unlock(&mut);
 
   pthread_cond_signal(&needFree); // Wake up the writeback thread so it will exit.
   pthread_join(worker, 0);
 
   // XXX flush range should return an error number, which we would check.  (Right now, it aborts...)
-  stasis_dirty_page_table_flush_range(stasis_runtime_dirty_page_table(), 0, 0);
+  stasis_dirty_page_table_flush(stasis_runtime_dirty_page_table());
 
   struct LH_ENTRY(list) iter;
   const struct LH_ENTRY(pair_t) * next;
@@ -367,7 +386,9 @@ static void bhBufDeinit() {
   page_handle->close(page_handle);
 }
 static void bhSimulateBufferManagerCrash() {
+  pthread_mutex_lock(&mut);
   running = 0;
+  pthread_mutex_unlock(&mut);
 
   pthread_cond_signal(&needFree);
   pthread_join(worker, 0);
@@ -408,6 +429,8 @@ void stasis_buffer_manager_hash_open(stasis_page_handle_t * h) {
   stasis_buffer_manager_close = bhBufDeinit;
   stasis_buffer_manager_simulate_crash = bhSimulateBufferManagerCrash;
 
+  flushing = 0;
+
   stasis_buffer_pool = stasis_buffer_pool_init();
 
   lru = lruFastInit(pageGetNode, pageSetNode, 0);

src/stasis/bufferManager/legacy/pageFile.c

@@ -77,6 +77,7 @@ static void pfPageRead(stasis_page_handle_t * h, Page *ret, pagetype_t type) {
     dirty page table can be kept up to date. */
 static void pfPageWrite(stasis_page_handle_t * h, Page * ret) {
   /** If the page is clean, there's no reason to write it out. */
+  assertlocked(ret->rwlatch);
   if(!stasis_dirty_page_table_is_dirty(h->dirtyPages, ret)) {
     DEBUG(" =^)~ ");
     return;

src/stasis/bufferManager/pageArray.c

@@ -44,7 +44,9 @@ static Page* paGetCachedPage(int xid, pageid_t page) {
   return paLoadPage(xid, page, UNKNOWN_TYPE_PAGE);
 }
 static void paReleasePage(Page * p) {
+  writelock(p->rwlatch,0);
   stasis_dirty_page_table_set_clean(stasis_runtime_dirty_page_table(), p);
+  unlock(p->rwlatch);
 }
 
 static int paWriteBackPage(pageid_t p) { return 0;  /* no-op */ }

src/stasis/dirtyPageTable.c

@@ -51,6 +51,7 @@ void stasis_dirty_page_table_set_dirty(stasis_dirty_page_table_t * dirtyPages, P
 
 void stasis_dirty_page_table_set_clean(stasis_dirty_page_table_t * dirtyPages, Page * p) {
   pthread_mutex_lock(&dirtyPages->mutex);
+  assertlocked(p->rwlatch);
   dpt_entry dummy = {p->id, 0};
   const dpt_entry * e = rbdelete(&dummy, dirtyPages->table);
 
@@ -69,6 +70,8 @@ void stasis_dirty_page_table_set_clean(stasis_dirty_page_table_t * dirtyPages, P
 int stasis_dirty_page_table_is_dirty(stasis_dirty_page_table_t * dirtyPages, Page * p) {
   int ret;
   pthread_mutex_lock(&dirtyPages->mutex);
+  assertlocked(p->rwlatch);
+
   ret = p->dirty;
   dpt_entry e = { p->id, 0};
   const void* found = rbfind(&e, dirtyPages->table);
@@ -94,12 +97,39 @@ lsn_t stasis_dirty_page_table_minRecLSN(stasis_dirty_page_table_t * dirtyPages)
 pageid_t stasis_dirty_page_table_dirty_count(stasis_dirty_page_table_t * dirtyPages) {
   pthread_mutex_lock(&dirtyPages->mutex);
   pageid_t ret = dirtyPages->count;
+  assert(dirtyPages->count >= 0);
   pthread_mutex_unlock(&dirtyPages->mutex);
   return ret;
 }
 
 void stasis_dirty_page_table_flush(stasis_dirty_page_table_t * dirtyPages) {
-  stasis_dirty_page_table_flush_range(dirtyPages, 0, 0); // pageid_t = 0 means flush to EOF.
+  dpt_entry dummy = { 0, 0 };
+  const int stride = 200;
+  pageid_t vals[stride];
+  int off = 0;
+  int strides = 0;
+  pthread_mutex_lock(&dirtyPages->mutex);
+  for(const dpt_entry * e = rblookup(RB_LUGTEQ, &dummy, dirtyPages->table) ;
+        e;
+        e = rblookup(RB_LUGREAT, &dummy, dirtyPages->table)) {
+    dummy = *e;
+    vals[off] = dummy.p;
+    off++;
+    if(off == stride) {
+      pthread_mutex_unlock(&dirtyPages->mutex);
+      for(pageid_t i = 0; i < off; i++) {
+        writeBackPage(vals[i]);
+      }
+      off = 0;
+      strides++;
+      pthread_mutex_lock(&dirtyPages->mutex);
+    }
+  }
+  pthread_mutex_unlock(&dirtyPages->mutex);
+  for(int i = 0; i < off; i++) {
+    writeBackPage(vals[i]);
+  }
+//  if(strides < 5) { DEBUG("strides: %d dirtyCount = %lld\n", strides, stasis_dirty_page_table_dirty_count(dirtyPages)); }
 }
 void stasis_dirty_page_table_flush_range(stasis_dirty_page_table_t * dirtyPages, pageid_t start, pageid_t stop) {
 
@@ -121,12 +151,13 @@ void stasis_dirty_page_table_flush_range(stasis_dirty_page_table_t * dirtyPages,
       if(stop && (err == EBUSY)) { abort(); /*api violation!*/ }
   }
   free(staleDirtyPages);
-  forcePageRange(start*PAGE_SIZE,stop*PAGE_SIZE);
+//  forcePageRange(start*PAGE_SIZE,stop*PAGE_SIZE);
 }
 
 stasis_dirty_page_table_t * stasis_dirty_page_table_init() {
   stasis_dirty_page_table_t * ret = malloc(sizeof(*ret));
   ret->table = rbinit(dpt_cmp, 0);
+  ret->count = 0;
   pthread_mutex_init(&ret->mutex, 0);
   return ret;
 }

src/stasis/operations/lsmTree.c

@@ -57,6 +57,7 @@ void TlsmRegionForceRid(int xid, void *conf) {
     pageid_t pid;
     Tread(xid,a.regionList,&pid);
     stasis_dirty_page_table_flush_range(stasis_runtime_dirty_page_table(), pid, pid+a.regionSize);
+    forcePageRange(pid, pid+a.regionSize);
     //    TregionDealloc(xid,pid);
   }
 }

src/stasis/pageHandle.c

@@ -13,9 +13,8 @@ static void phWrite(stasis_page_handle_t * ph, Page * ret) {
   // This lock is only held to make the page implementation happy.  We should
   // implicitly have exclusive access to the page before this function is called,
   // or we'll deadlock.
-
-  /// TODO Turn into trywritelock + test for trouble.
-  writelock(ret->rwlatch,0);
+  int locked = trywritelock(ret->rwlatch,0);
+  assert(locked);
   if(!ret->dirty) { unlock(ret->rwlatch); return; }
   stasis_page_flushed(ret);
   if(ph->log) { stasis_log_force(ph->log, ret->LSN, LOG_FORCE_WAL); }
@@ -29,7 +28,8 @@ static void phWrite(stasis_page_handle_t * ph, Page * ret) {
   unlock(ret->rwlatch);
 }
 static void phRead(stasis_page_handle_t * ph, Page * ret, pagetype_t type) {
-  writelock(ret->rwlatch,0);
+  int locked = trywritelock(ret->rwlatch,0);
+  assert(locked);
   int err = ((stasis_handle_t*)ph->impl)->read(ph->impl, PAGE_SIZE * ret->id, ret->memAddr, PAGE_SIZE);
   if(err) {
     if(err == EDOM) {
@@ -50,7 +50,7 @@ static void phForce(stasis_page_handle_t * ph) {
   assert(!err);
 }
 static void phForceRange(stasis_page_handle_t * ph, lsn_t start, lsn_t stop) {
-  int err = ((stasis_handle_t*)ph->impl)->force_range(ph->impl,start,stop);
+  int err = ((stasis_handle_t*)ph->impl)->force_range(ph->impl,start*PAGE_SIZE,stop*PAGE_SIZE);
   assert(!err);
 }
 static void phClose(stasis_page_handle_t * ph) {

src/stasis/truncation.c

@@ -1,5 +1,5 @@
 #include <stasis/truncation.h>
-
+#include <stdio.h>
 struct stasis_truncation_t {
   char initialized;
   char automaticallyTruncating;
@@ -104,7 +104,7 @@ int stasis_truncation_truncate(stasis_truncation_t* trunc, int force) {
     } else {
       lsn_t flushed = trunc->log->first_unstable_lsn(trunc->log, LOG_FORCE_WAL);
       if(force || flushed - log_trunc > 2 * TARGET_LOG_SIZE) {
-	//fprintf(stderr, "Flushing dirty buffers: rec_lsn = %ld log_trunc = %ld flushed = %ld\n", rec_lsn, log_trunc, flushed);
+        DEBUG("Flushing dirty buffers: rec_lsn = %lld log_trunc = %lld flushed = %lld\n", rec_lsn, log_trunc, flushed);
         stasis_dirty_page_table_flush(trunc->dirty_pages);
 
         page_rec_lsn = stasis_dirty_page_table_minRecLSN(trunc->dirty_pages);

stasis/bufferManager.h

@@ -155,6 +155,9 @@ extern void (*forcePages)();
     Force written back pages that fall within a particular range to disk.
 
     This does not force page that have not been written to with pageWrite().
+
+    @param start the first pageid to be forced to disk
+    @param stop the page after the last page to be forced to disk.
 */
 extern void (*forcePageRange)(pageid_t start, pageid_t stop);
 extern void (*stasis_buffer_manager_simulate_crash)();

stasis/pageHandle.h

@@ -61,6 +61,10 @@ struct stasis_page_handle_t {
      as well...)
   */
   void (*force_file)(struct stasis_page_handle_t* ph);
+  /**
+   * @param start the pageid of the first page to be forced to disk.
+   * @param stop the pageid of the page after the last page to be forced to disk.
+   */
   void (*force_range)(struct stasis_page_handle_t* ph, lsn_t start, lsn_t stop);
   /**
      Force the page file to disk, then close it.