diff --git a/src/data/ellpack_page_raw_format.cu b/src/data/ellpack_page_raw_format.cu
index 445b08699523..2f54b91c9bbc 100644
--- a/src/data/ellpack_page_raw_format.cu
+++ b/src/data/ellpack_page_raw_format.cu
@@ -28,7 +28,6 @@ class EllpackPageRawFormat : public SparsePageFormat<EllpackPage> {
     if (!fi->Read(&impl->base_rowid)) {
       return false;
     }
-    std::cout << "impl brd:" << impl->base_rowid << std::endl;
     return true;
   }
 
@@ -42,7 +41,6 @@ class EllpackPageRawFormat : public SparsePageFormat<EllpackPage> {
     bytes += sizeof(impl->is_dense);
     fo->Write(impl->row_stride);
     bytes += sizeof(impl->row_stride);
-    std::cout << "write brd:" << impl->base_rowid << std::endl;
     CHECK(!impl->gidx_buffer.ConstHostVector().empty());
     fo->Write(impl->gidx_buffer.HostVector());
     bytes += impl->gidx_buffer.ConstHostSpan().size_bytes() + sizeof(uint64_t);
diff --git a/src/data/ellpack_page_source.cu b/src/data/ellpack_page_source.cu
index d5ffdc4aa377..fb414f4aef79 100644
--- a/src/data/ellpack_page_source.cu
+++ b/src/data/ellpack_page_source.cu
@@ -24,7 +24,6 @@ void EllpackPageSource::Fetch() {
     auto *impl = this->page_->Impl();
     *impl = EllpackPageImpl(device_, *cuts_, *csr, is_dense_, row_stride_, feature_types_);
     page_->SetBaseRowId(csr->base_rowid);
-    std::cout << "csr br:" << csr->base_rowid << std::endl;
     this->WriteCache();
   }
 }
diff --git a/src/data/sparse_page_source.h b/src/data/sparse_page_source.h
index 690ef4f864b4..b07178c496f3 100644
--- a/src/data/sparse_page_source.h
+++ b/src/data/sparse_page_source.h
@@ -117,7 +117,7 @@ class SparsePageSourceImpl : public BatchIteratorImpl<S> {
     }
     // An heuristic for number of pre-fetched batches.  We can make it part of BatchParam
     // to let user adjust number of pre-fetched batches when needed.
-    uint32_t constexpr kPreFetch = 1;
+    uint32_t constexpr kPreFetch = 4;
 
     size_t n_prefetch_batches = std::min(kPreFetch, n_batches_);
     CHECK_GT(n_prefetch_batches, 0) << "total batches:" << n_batches_;
@@ -140,7 +140,6 @@ class SparsePageSourceImpl : public BatchIteratorImpl<S> {
 
         std::uint64_t offset = self->cache_info_->offset.at(fetch_it);
         std::uint64_t length = self->cache_info_->bytes.at(fetch_it);
-        // std::cout << typeid(S).name() << " offset:" << offset << " length:" << length << std::endl;
 
         auto fi = std::make_unique<common::PrivateMmapStream>(n, true, offset, length);
         CHECK(fmt->Read(page.get(), fi.get()));