diff --git a/src/unix/syscall.c b/src/unix/syscall.c
index 0fc7804c0..2c4221cca 100755
--- a/src/unix/syscall.c
+++ b/src/unix/syscall.c
@@ -498,6 +498,7 @@ closure_function(9, 2, void, sendfile_bh,
                 thread_log(t, "   rewound %ld bytes to %ld", rewind, f_in->offset);
             }
             rv = bound(written) == 0 ? -EAGAIN : bound(written);
+            sg_buf_release(bound(cur_buf));
             thread_log(t, "   write would block, returning %ld", rv);
         } else {
             thread_log(t, "   zero or error, rv %ld", rv);
@@ -523,7 +524,6 @@ closure_function(9, 2, void, sendfile_bh,
     } else {
         bound(written) += rv;
         bound(cur_buf)->misc += rv;
-        assert(bound(cur_buf)->length >= rv);
         if (bound(cur_buf)->misc == bound(cur_buf)->length) {
             sg_buf_release(bound(cur_buf));
             if (bound(written) == bound(readlen)) {
@@ -534,6 +534,7 @@ closure_function(9, 2, void, sendfile_bh,
             assert(bound(cur_buf) != INVALID_ADDRESS);
             bound(cur_buf)->misc = 0; /* offset for our use */
         }
+        assert(bound(cur_buf)->misc < bound(cur_buf)->length);
     }
 
     /* issue next write */
diff --git a/src/x86_64/pagecache.c b/src/x86_64/pagecache.c
index 69859ed17..ab92d125d 100644
--- a/src/x86_64/pagecache.c
+++ b/src/x86_64/pagecache.c
@@ -491,7 +491,7 @@ static inline void page_list_init(struct pagelist *pl)
 
 u64 pagecache_drain(pagecache pc, u64 drain_bytes)
 {
-    u64 pages = drain_bytes >> pc->page_order;
+    u64 pages = pad(drain_bytes, pagecache_pagesize(pc)) >> pc->page_order;
     spin_lock(&pc->lock);
     u64 evicted = evict_pages_cache_locked(pc, pages);
     spin_unlock(&pc->lock);
diff --git a/src/x86_64/service.c b/src/x86_64/service.c
index 743215208..90b4e9c98 100644
--- a/src/x86_64/service.c
+++ b/src/x86_64/service.c
@@ -127,7 +127,7 @@ void mm_service(void)
     u64 free = heap_total(p) - heap_allocated(p);
     mm_debug("%s: total %ld, alloc %ld, free %ld\n", __func__, heap_total(p), heap_allocated(p), free);
     if (free < CACHE_DRAIN_CUTOFF) {
-        u64 drain_bytes = CACHE_DRAIN_CUTOFF - free + PAGESIZE - 1;
+        u64 drain_bytes = CACHE_DRAIN_CUTOFF - free;
         u64 drained = pagecache_drain(global_pagecache, drain_bytes);
         if (drained > 0)
             mm_debug("   drained %ld / %ld requested...\n", drained, drain_bytes);