From c9d8f3e4f145bfdbdf72579075999ed0b84275c7 Mon Sep 17 00:00:00 2001
From: David Young <dyoung@hdfgroup.org>
Date: Wed, 15 Jul 2020 16:44:52 -0500
Subject: Log the number of page-buffer accesses at various multiples of the
 page size with log outlet `pb_access_sizes`.

---
 src/H5PB.c        | 42 ++++++++++++++++++++++++++++++++++++++++++
 src/H5PBprivate.h |  1 +
 2 files changed, 43 insertions(+)

diff --git a/src/H5PB.c b/src/H5PB.c
index b0aae86..794e6ed 100644
--- a/src/H5PB.c
+++ b/src/H5PB.c
@@ -122,6 +122,8 @@ static herr_t metadata_multipart_read(H5F_shared_t *, H5FD_mem_t, haddr_t,
 static herr_t metadata_multipart_write(H5F_shared_t *, H5FD_mem_t, haddr_t,
     size_t, const void *);
 
+static void H5PB_log_access_by_size_counts(const H5PB_t *);
+
 /*********************/
 /* Package Variables */
 /*********************/
@@ -148,6 +150,7 @@ H5FL_DEFINE_STATIC(H5PB_entry_t);
 
 HLOG_OUTLET_DECL(pagebuffer);
 HLOG_OUTLET_SHORT_DEFN(pagebuffer, all);
+HLOG_OUTLET_SHORT_DEFN(pb_access_sizes, pagebuffer);
 HLOG_OUTLET_SHORT_DEFN(pbflush, pagebuffer);
 HLOG_OUTLET_SHORT_DEFN(pbflush_entry, pbflush);
 HLOG_OUTLET_SHORT_DEFN(pbio, pagebuffer);
@@ -714,6 +717,8 @@ H5PB_dest(H5F_shared_t *shared)
 
         pb_ptr = shared->pb_ptr;
 
+        H5PB_log_access_by_size_counts(pb_ptr);
+
         HDassert(pb_ptr->magic == H5PB__H5PB_T_MAGIC);
 
         /* the current implementation if very inefficient, and will 
@@ -913,6 +918,37 @@ done:
 
 } /* H5PB_page_exists */
 
+static void
+H5PB_count_access_by_size(H5PB_t *pb, size_t size)
+{
+    const size_t nslots = NELMTS(pb->access_size_count);
+    size_t i, hi;
+
+    for (hi = pb->page_size, i = 0; i < nslots - 1; i++, hi *= 2){
+        if (size <= hi)
+            break;
+    }
+    pb->access_size_count[i]++;
+}
+
+static void
+H5PB_log_access_by_size_counts(const H5PB_t *pb)
+{
+    const size_t nslots = NELMTS(pb->access_size_count);
+    size_t i, lo, hi;
+
+    for (lo = 0, hi = pb->page_size, i = 0;
+         i < nslots - 1;
+         i++, lo = hi + 1, hi *= 2) {
+        hlog_fast(pb_access_sizes,
+            "%p %16" PRIu64 " accesses %8zu - %8zu bytes long",
+            (const void *)pb, pb->access_size_count[i], lo, hi);
+    }
+    hlog_fast(pb_access_sizes,
+        "%p %16" PRIu64 " accesses %8zu - greater  bytes long",
+        (const void *)pb, pb->access_size_count[i], lo);
+}
+
 
 /*-------------------------------------------------------------------------
  *
@@ -1072,6 +1108,9 @@ H5PB_read(H5F_shared_t *shared, H5FD_mem_t type, haddr_t addr, size_t size,
 
     pb_ptr = shared->pb_ptr;
 
+    if (pb_ptr != NULL)
+        H5PB_count_access_by_size(pb_ptr, size);
+
     HDassert(pb_ptr == NULL || pb_ptr->magic == H5PB__H5PB_T_MAGIC);
 
     /* Bypass the page buffer in case
@@ -1956,6 +1995,9 @@ H5PB_write(H5F_shared_t *shared, H5FD_mem_t type, haddr_t addr, size_t size,
 
     pb_ptr = shared->pb_ptr;
 
+    if (pb_ptr != NULL)
+        H5PB_count_access_by_size(pb_ptr, size);
+
     if ( pb_ptr == NULL ) {
 
         bypass_pb = TRUE; /* case 1) -- page buffer is disabled */
diff --git a/src/H5PBprivate.h b/src/H5PBprivate.h
index 6b879c7..983d183 100644
--- a/src/H5PBprivate.h
+++ b/src/H5PBprivate.h
@@ -610,6 +610,7 @@ typedef struct H5PB_t {
     int64_t flushes[H5PB__NUM_STAT_TYPES];
     int64_t evictions[H5PB__NUM_STAT_TYPES];
     int64_t clears[H5PB__NUM_STAT_TYPES];
+    uint64_t access_size_count[6];
     int64_t max_lru_len;
     int64_t max_lru_size;
     int64_t lru_md_skips;
-- 
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